Plant Stress

Water your CT Garden with Confidence

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By: Heather Zidack, UConn Home Garden Education Office

Watering is an essential skill for gardeners that is often overlooked. “How often should I water and how much?” is a frequent question with new gardens or when establishing new plants.  

There’s no magic formula for watering your plants. The soil texture, local climate, and even the metabolism of your plants can affect how often water needs to be replenished. So how do we know what to do? Over time, experienced gardeners form a sense of their soil and their plant’s needs, and perfect their watering practices.   

Pepper plant growing in a garden bed with a drip irrigation hose nearby.What plants really need 

Most established garden plants require about 1 inch of water per week from rainfall and irrigation combined. When mother nature doesn’t provide this through rainfall, we can supplement by adding about 0.62 gallons of water per square foot in a garden bed.  However, actual needs vary with soil type, weather conditions, plant species, and stage of growth.   

Knowing your soil texture can help you anticipate what your watering schedule might look like. Sandy soils are known for rapid drainage, which often means they require more frequent watering. Clay soils, on the other hand, hold water for longer periods and generally need less frequent irrigation. Plants also have preferences for different soil types, many of which are related to water availability and drainage. Choosing the right plant for the right site can help ensure it receives adequate moisture. 

A plant's water demand may vary depending on its stage of growth. For example, we tend to encourage additional support for plants that are fruiting/flowering, or plants that have just recently been transplanted. Keep a close eye on these plants and their water needs during stressful periods. Newly planted trees, shrubs and perennials need this additional monitoring and support through their first year of establishment in the landscape. You may find that you’re watering them more frequently during this time. This can be totally normal.  

Sometimes, soil can appear dark even when it hasn’t been watered, so don’t rely on appearances alone.  Your hands are one of the most reliable tools for checking soil moisture. Dig a few inches below the surface and feel the soil. If it feels cool and slightly moist, watering can likely wait. If it feels dry and crumbly, it's time to water. If the soil feels saturated or releases water when squeezed, allow it to dry somewhat before watering again. 

Water Deeply 

Giving your plants a good soak does more than just help them in the short term. Deep watering provides a slow, thorough soak that reaches the plant’s root zone rather than just the soil surface. This encourages deeper root growth and can improve drought tolerance, often allowing for less frequent watering. For most vegetables and perennials, water should reach at least 6–12 inches into the soil. Trees and shrubs may benefit from moisture penetrating even deeper into the root zone. 

Apply water slowly at the dripline so it soaks in without pooling or running off. Use a soaker hose, or a regular hose on a slow trickle over the root zone of your plants. Avoid high-flow sprinklers, since they may cause runoff. Keep in mind that water movement depends on soil type.  

Check the soil every so often to ensure that water is penetrating deep enough and set a timer for yourself. After a few watering cycles, you will become familiar with the timing and flow rate for your specific soil and plants. 

Stay Consistent 

Don’t automatically change your watering habits just because the temperature changes.  Hot weather can increase water demand, but it is essential to always check the soil first. During periods of heat and drought stress, plants can close their stomata and reduce water use as a survival mechanism. While this may slow water uptake, plants still need adequate soil moisture. Overwatering, however, may not be helpful. Instead, roots can sit in saturated soil and develop diseases like root rot. Always check the top few inches of soil to ensure water is needed. 

When weather starts to cool off in the fall, continue your watering practices. By watering until the ground freezes, you help your plants, survive the winter. The effects of winter burn can be reduced when evergreens enter the winter properly hydrated.  

Watering is an essential task in the garden year-round. It is important to know your plants, your soil, and the climate you are growing in to ensure you are giving your plants enough hydration. By watering only when needed, watering deeply, and continuing these practices well into the fall, you will be sure to have healthy plants year round! 

The UConn Home Garden Education Office supports UConn Extension’s mission by providing answers you can trust with research-based information and resources. For gardening questions, contact us toll-free at (877) 486-6271, visit our website at homegarden.cahnr.uconn.edu, or reach out to your local UConn Extension center at extension.uconn.edu/locations.   

This article was published in the Hartford Courant July 11, 2026

What’s Going Down with Your CT Basil This Summer?

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By: N. Raymond and Emily Leahy, UConn Home Garden Education Office

What's Going Down with Your CT Basil This Summer?
By: N. Raymond and Emily Leahy, UConn Home Garden Education Office 

Basil growth is ramping up as we enter July. As these tasty plants begin to flourish, it’s important to keep an eye out for a pathogen known as downy mildew. Basil downy mildew (Peronospora belbahrii) severely impacts numerous varieties of basil (Ocimum spp.)  worldwide. The disease, caused by an oomycete pathogen, is especially prevalent in sweet basil (Ocimum basilicum). Oomycetes, also known as water molds, behave similarly to fungi yet are equipped with different structures and means of infecting plant material. Using water or water-based secretions, their reproductive cells (known as zoospores) adhere to the surfaces of plant tissue to inoculate their hosts.  

Leaves suffering from basil downy mildew exhibit yellow/pale discoloration (chlorosis) and browning on their upper surfaces. Chlorotic lesions expand and become necrotic, with leaves eventually falling prematurely. Small sac-like structures develop on the underside of leaves and are visible as purple-gray dots. These are called sporangia, which are specialized structures that can form, store, and release spores. Basil downy mildew prefers moist and humid conditions that encourage the growth and development of the pathogen.  

P. belbahrii must occupy a living host to survive and reproduce, making it an obligate parasite. The pathogen can only overwinter in warm environments where hosts will not freeze during cold temperatures. Sporangia germinate on hosts under high humidity and moderate temperatures. The germ tube of P. belbahrii enters basil leaves through microscopic openings called stomata where it can grow, expanding what is known as its hyphae network (filamentous growth structures of fungi and oomycetes) between plant cells. As the disease progresses, P. belbahrii will colonize the leaves, stems, and seeds of its host. Symptoms are often visible within 5-10 days of inoculation. However, infected hosts may also appear asymptomatic. Typically, sporulation of P. belbahrii occurs at night in conjunction with moist and humid conditions. Sporangiophores break through stomata on the underside of leaves, from which sporangia are released and travel to inoculate new leaves. Extended periods of leaf wetness, accompanied by moderate temperatures and high humidity, encourages prolific growth of P. belbahrii.  

Basil downy mildew can be controlled through cultural and chemical methods. Since P.  belbahrii thrives in moist conditions, it is crucial to maintain proper air circulation and space between plants. This can be achieved by planting at appropriate distances when you start your garden, or by thinning your plants later in the growing season. Planting seeds that are certified free of the pathogen minimizes the potential for disease as well. Utilizing drip irrigation or similar efficient watering systems can decrease standing moisture on and around basil plants. Avoid overhead watering or sprinkler systems. Fungicides are labeled for effective use against this pathogen, if chemical control is deemed necessary. Some cultivars with resistance to basil downy mildew are included in the table below.  

Type  Variety 
 

 

 

 

Sweet 

 Amazel 

Everleaf 

Evi 

Eleonora 

Prospera 

Prospera Active 

Rutgers Devotion 

Rutgers Obsession 

Rutgers Passion 

Rutgers Thunderstruck 
Purple  Red Rubin 

Prospera Red 
Scented  Sweet Dani (lemon) 

Lime Basil 

Our colleagues at Cornell have performed quite a bit of basil downy mildew research, which can be accessed at https://www.vegetables.cornell.edu/pest-management/disease-factsheets/basil-downy-mildew/. Visit this link to learn more. 

Have a question about plants? The UConn Home Garden Education Office supports UConn Extension’s mission by providing answers you can trust with research-based information and resources. For gardening questions, contact us toll-free at (877) 486-6271, visit our website at homegarden.cahnr.uconn.edu, or reach out to your local UConn Extension Center at extension.uconn.edu/locations. 

 

This article was published in the Hartford Courant July 4, 2026

Start Scouting Now for this Common CT Garden Pest

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By Heather Zidack, UConn Home Garden Education Office 

Close-up of a split green squash stem revealing orange plant tissue and a pale, grub-like larva inside, with soil visible in the background.Provide your feedback on BizChat
SVB larvae inside of a zucchini stem. Photo by H. Zidack

The Squash Vine Borer (SVB) is a red-orange and black winged insect. They emerge in early to mid-summer and lay their eggs at the base of squash stems. When those eggs hatch, larvae emerge and bore their way into the plant stem, continuing to eat your squash plants from the inside out until they are ready to pupate. Gardeners may not even notice their presence until they see squash plants wilting in the summer heat. Upon even closer inspection, a yellow, sawdust like appearance and entry hole at the base of the stem is often found. Once this is observed, it is often too late. While early June may feel too early to start scouting for these guys, it’s the perfect time to start planning defensive strategies to help protect your garden.  

The first thing you can do, especially if you have a history with these insects, is select resistant cultivars. Knowing which types of squash are common targets can help you determine whether you will want to keep a closer eye on them this season, or maybe plant something different, altogether.  

Cucurbita pepo is highly susceptible to Squash Vine Borer. This species includes Zucchini and summer squash. They have thin, hollow stems, which make it easy for these critters to get into. Pumpkins are also in this category. However, pumpkins are more likely to vine out and lay roots along the stems touching the soil surface. This helps the plant to withstand damage a bit better than its other counterparts.  

Cucurbita maxima, which includes winter squash like giant pumpkins, Kabocha and Blue Hubbard varieties, is also susceptible to the SVB. While it is less preferred than C. pepo, it can still be targeted. 

Cucurbita moschata is the most resistant plant species. C. moschata includes the butternut, honeynut and crookneck squashes. Their stems are thicker and more succulent, making them least favorable for the SVB to lay eggs on. Therefore, while not impossible, they stand a good chance against this garden pest.  These insects are also rarely found in cucumbers and melons.  

It is important to rotate your planting sites each year. These insects overwinter as pupae in the soil and emerge as adults in June-July. Planting in the same place each season is like placing a gift on their front doorstep. Moving your planting site and adding a protective row cover as soon as you plant can improve your odds at keeping the SVB away from your plants altogether. Leave the row cover until both male and female flowers begin to emerge. After that it is important to remove the row covers so pollinators can access the flowers.  

For gardeners unable to rotate their gardens, preventative measures can still be taken. Do not use row covers as they can trap the pest in with your plants. Some recommend placing aluminum foil around the first couple inches of stem at the soil line to prevent insects from laying eggs and boring through stem tissue. Treating the base of the plants with a preventative pesticide may also be effective.  

Chemical management is often tricky with these pests, and home gardeners may not feel it is worth the effort. Importantly, chemical management is no longer effective once the larvae have entered the stems, since they are then protected by the plants. In addition, these products can impact the pollinators visiting your cucurbits, so it’s important to carefully consider the full impact of chemical management. Always read the label in full and follow all instructions as prescribed.   

Start scouting for the adults early. In mid to late June, check the base of stems for eggs and early boring damage. You may even see the adult insects flying around. Symptoms, like wilting, often begin in late June and become more common in July. 

If you have a strong stomach and sense of adventure, you can carefully slice into the stem to try to find the larvae and extract it. Vining squash species may recover if the pest is removed and portions of vine are then buried in the soil, allowing new roots to take over and support the vine.   

Alternatively, removing affected plants entirely and disposing of them in the trash may help to break the life cycle and remove pests from your garden for future seasons.  

Since these insects typically only have one generation per year, your hard work does have a finish line. Paying extra attention and working to manage the SVB in early summer will allow your squash to grow healthy for the rest of the season. A second crop of summer squash can be planted in July, once adults are no longer out and laying eggs. This second crop should be unaffected by the SVB and produce healthy squash for your family to enjoy! 

The UConn Home Garden Education Office supports UConn Extension’s mission by providing answers you can trust with research-based information and resources. For gardening questions, contact us toll-free at (877) 486-6271, visit our website at homegarden.cahnr.uconn.edu, or reach out to your local UConn Extension Center at  extension.uconn.edu/locations.   

This article was published in the Hartford Courant June 7, 2026

Don’t Let Dry Soil Follow Your Plants Into Winter!

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By Holly McNamara, UConn Plant Diagnostic Lab

This year, Connecticut’s notably dry summer conditions have continued into fall. According to the U.S. Drought Monitor, all counties are abnormally dry for this time of year, and some are even considered to be in a moderate drought. Thus, many trees, shrubs, and perennials are heading into winter low on moisture. These conditions combined with the dry air, low precipitation, and fluctuating temperatures characteristic of Connecticut winters can lead to plant damage if no supplemental water is provided. Many of your plants will benefit from a deep final soak before the ground freezes.

Fall drought stress often doesn’t show up until spring, or even the following summer.Affected plants may appear perfectly normal and resume growth in the spring, using stored food energy. Plants may be weakened or die in late spring or summer when temperatures rise. Browning evergreens, delayed leaf-out, and sudden dieback are common signs of plants that went into winter too dry.

Moist soil is so important in the fall and winter months because it provides insulation to the roots. It may seem counter-intuitive, but properly hydrated soil does a much better job at protecting roots from freezing temperatures than dry soil. Root damage occurs for this reason when plants do not receive enough late-season moisture.

Woody plants with shallow root systems require the most supplemental water during extended dry periods in the fall and winter. Trees in this category include maples, birches, willows, and dogwoods. This category also includes perennials, and shrubs like hydrangeas, boxwoods, and azaleas. These plants benefit from mulch to further conserve soil moisture and buffer the roots from temperature swings. Apply mulch about 2 to 4 inches away from the trunk all the way to the outermost reach of its branches in a doughnut shape.

Evergreen needles up close
Evergreens need sufficient water in dry falls to help prevent winter injury. Photo by Heather Zidack

Evergreens also benefit from fall and winter watering because they do not go dormant in the winter. Evergreens of any age are still actively respiring during the coldest months of the year and will continuously lose water through their needles. If they go into the winter with dry soil, they are more likely to have a difficult spring recovery. This is especially true for those in open or windy areas.

Only water when daytime temperatures are above 40°F, ideally in the late morning or early afternoon so the water can soak in before possible freezing at night. Feel the soil at a depth of 4 to 6 inches to ensure that supplemental water is necessary. Soil should be consistently moist, but not oversaturated or muddy. Stop supplemental watering after the ground freezes because plants cannot absorb water through frozen soil. To water, use a soaker hose to provide a slow stream of water that can penetrate deeper into the soil with limited runoff. If your hose is already stored away for the winter, and your tree or shrub is small, consider drilling a 1/8-inch hole at the bottom of a 5-gallon bucket and filling that with water for a slow, steady stream. If dry weather continues into the winter and there’s little snow cover, additional watering once or twice a month may be needed until the soil hardens.

A final round of watering now can prevent root injury that won’t be visible until much later. Evergreens, deciduous trees, and other landscape plantings will head into winter stronger with a little extra attention this month. Giving the soil one last watering before it freezes is one of the simplest ways to protect your landscape from winter stress.

The UConn Home & Garden Education Center supports UConn Extension’s mission by providing answers you can trust with research-based information and resources. For gardening questions, contact us toll-free at (877) 486-6271, visit our website at homegarden.cahnr.uconn.edu, or reach out to your local UConn Extension center at extension.uconn.edu/locations.

This article was published in the Hartford Courant October 25, 2025

Why is My Lilac Blooming in the Fall?

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By Pamm Cooper, UConn Home & Garden Education Center

Bumblebees on fall blooming lilacs
Photo by Pamm Cooper, UConn Home & Garden Education Center

Spring-blooming woody plants like lilacs (especially the old, grafted varieties), ornamental cherries, forsythia, crabapples, azaleas and some magnolias set their flower buds for the following year in early summer shortly after flowering.  Usually, flower buds are triggered to bloom by environmental conditions which normally occur after an extended fall and winter cold period, followed by longer days and warming temperatures in spring. It is not typical for these plants to have a second bloom in the fall, but environmental conditions sometimes trigger premature flowering in the fall. Some plants may have only a few flowers rebloom, while other plants may have more flowers open in the fall.  

Some of the reasons for this out of season bloom are extended summer heat and drought conditions where supplemental water is lacking.  Severe early defoliation, especially from certain fungal pathogens, can also contribute to reblooming. The past two springs have been very wet and diseases such as anthracnose and Pseudocercospora spp. leaf spot may have caused leaves to brown, shrivel and drop early. This stresses the shrub and contributes to out of sync rebloom if other conditions are right. Good sanitation practices such as cleaning up infected leaves will be helpful in reducing fungal infections the following year. 

If a plant is healthy and relatively unstressed, the normal seasonal move to cooler weather triggers dormancy. Plants that are deciduous will drop leaves as daylight length and temperature both decrease. Next year’s leaf and flower buds will also remain in a dormant state. Flowering and leafing out will be triggered by increasing daylight and air temperatures the next spring. 

Lilac flowers opening in October
Photo by Pamm Cooper, UConn Home & Garden Education Center

If certain woody plants have been stressed during the growing season, however, the change to cooler weather followed by some warmer weather can trigger some of the flower buds to open prematurely. This false dormancy especially affects flower buds near the tops of old-style lilacs where it is sunnier and warmer. Ornamental cherries may show sporadic flowering all over the tree where there is a southern exposure.  

While fall reblooming of ornamental trees and shrubs can lead to a disappointing floral display the following spring, it is not harmful to the plant. After a less showy spring bloom period, flower buds will be produced normally. If stressful conditions caused by environmental conditions, insect pests or fungal pathogens are minimal, then a second bloom in autumn is unlikely to occur. Gardeners and landscapers can only do so much, and while the weather is out of our control, making sure plants are maintained properly to avoid stress during the summer will go a long way in helping them remain as healthy as possible.  

The UConn Home & Garden Education Center supports UConn Extension’s mission by providing answers you can trust with research-based information and resources. For gardening questions, contact us toll-free at (877) 486-6271, visit our website at homegarden.cahnr.uconn.edu, or reach out to your local UConn Extension center at extension.uconn.edu/locations.

This article was published in the Hartford Courant October 18, 2025

Dodder – A Common but Weird Parasitic Plant

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By Pamm Cooper, UConn Home & Garden Education Center

Dodder plant wrapped around a host and flowering
Photo by Pamm Cooper, UConn Home & Garden Education Center

Dodder is an obligate parasite of certain plants. This unusual member of the morning glory family is also known as “Angel’s Hair” and “Strangle Weed.” Like Indian pipe, another parasitic plant, Dodder has no chlorophyll to manufacture its own food, so nutrients and water are obtained from its host plant.  Its yellow to orange twining stems can form stringy, dense orange mats that cover its host plants, and it will often climb over other nearby plants as well. This vine twines counterclockwise around stems and other parts of its host.  Look for it in mid- July through September in damp fields or on stream and pond banks. 

Dodder germinates from seeds produced in earlier years. The new plants have only a few days to find a suitable host plant, or they will die. After connecting with the host plant, dodder will degrade at the soil level where it originated and is then free of any soil contact. Dodder has no leaves or roots, but it does produce flowers and then seeds.  The only way new plants can be re-established is from seed produced at least the previous year or even earlier.  

Dodder feeds on its host by means of small tubes called haustoria that pierce into the hosts leaf or stem vascular system. One type will siphon water from the xylem, and another type will obtain food (minerals, sugars etc.) from the phloem of the host plant. In this way, dodder obtains essential nutrients and water for its own survival at the expense of its host plant. Five-angled dodder Cuscuta pentagona, a very common dodder species found here in Connecticut does not have specialized host plant preferences. 

Since not all plants are suitable hosts for dodder, and because it needs to find a host quickly, dodder has a unique ability to “sniff out” certain plant chemicals and will gravitate toward these plants soon after germination. Notable hosts are jewelweed in the wild and tomatoes in crop cultivation. Thus, if you are interested in finding dodder, in July and August check out places where jewelweed abounds. Look for mats of orange, stringy vines covering the tops of this plant and perhaps on nearby Joe-pye weed and goldenrods.  

Yellow strings of dodder encompassing plants in a field
Photo by Pamm Cooper, UConn Home & Garden Education Center

Dodder seeds can survive in soil for twenty years or more and will germinate as conditions are suitable. Because of the longevity of its seed viability, dodder may be found either yearly in the same area or appear there years later. Flooding can also relocate the seeds, so it may appear along various spots along the same stream or pond. Look for its small white flowers appearing in clusters along the vine in late July and August. 

Once dodder is firmly established on the host plant in the wild, research has shown that removal of the host plants and the dodder, especially before seeds are set on the dodder, will be more effective than other methods. This may need to be done yearly until any seed bank is exhausted. Try to scout early in July as dodder is getting established. Sometimes small dodder plants can be removed from the host. Some people with dodder persisting in extensive areas have burned these sites, and this will also severely impact any seeds on the ground. 

Dodder is an aggressive plant, but it is not considered invasive because it is a native plant. It has received the dubious honor of making the Federal List of Noxious Weeds, though.  Although its hosts may be severely weakened, dodder does not always kill its host. While that is not reasonable cause to let it run rampant in a garden, in the wild it is in more of a tournament for survival. May the best plant win… 

The UConn Home & Garden Education Center supports UConn Extension’s mission by providing answers you can trust with research-based information and resources. For gardening questions, contact us toll-free at (877) 486-6271, visit our website at homegarden.cahnr.uconn.edu, or reach out to your local UConn Extension center at cahnr.uconn.edu/extension/locations. 

This article was published in the Hartford Courant September 1, 2025

Extreme Sports for Plants: Temperature Tolerance

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By Dr. Matthew Lisy, UConn Adjunct Faculty

Spathiphyllum wallisii in a pot wilting indoors

This Spathiphyllum wallisii is forty years old. In the fall of 2024, it wilted due to an extreme negative temperature change. (photo by M. Lisy)

Spathiphyllum wallisii outside, lush and healthy

This is the same Spathiphyllum wallisii showing a lot of new growth during the warm, humid summer of 2025. (photo by M. Lisy)

Plants, like humans, have an ideal temperature preference.  In general, we like to have temperatures between 60 to 80 degrees Fahrenheit.  Temperatures outside this range cause us stress.  Our plants have very similar temperature requirements, only they have no ability to shiver or move!  This past winter, I had a 40-year-old houseplant near my bedroom window.  Our fall weather hit, and we dropped about 30 degrees in a day.  My plant wilted and looked like it was going to die.  After a long process of investigation and discussions with my fellow plant professionals, I can only conclude it was the rapid temperature change.  The good news is that it made a full recovery once it adapted to the cooler weather.

This past winter, I had some Sansevieria that were under my windowsill.  They get beautiful light in the later part of the day.  The house is heated to 55 degrees, which is above their lower temperature tolerance, but the plants were not looking good.  This spring, I found out that the storm window had fallen out of place.  This set up a cold draft that negatively affected the plants, causing some formerly unexplained rot over the winter.

Not all plants have the same susceptibility to temperature.  Cacti and succulents are usually from hot, arid climates.  These plants are used to seeing temperatures soaring in the day, and then getting comparatively cold at night.  As long as they are given proper light, most of these plants can tolerate life very easily in our homes.  Even cold, unheated basements or outdoor greenhouses are just fine as long as temperatures stay above freezing.

Many of our plants come from the tropical forest floor where they are used to similar temperatures during the day and the night, all year long.  While there is some adaptation to life in our homes, they have a preferred temperature and humidity range.  There are some really neat “new” Philodendron species being offered for sale.  Many of them have minimum temperatures of 60 or even 65.  This can be difficult to do in an era where our smart thermostats are programed to turn down while we are not home, and up when we return in the evening.  These temperature swings may be intolerable to our plants.

Be careful watering plants when the sun is shining.  Those little water droplets can end up capturing the sun’s rays just like a greenhouse would.  The droplets heat up and can actually burn a spot in the plant leaf.  Remember, each drop can do this, so many times, the whole plant can look like a spotted mess!

Temperature can many times mark the difference between success and failure to keep some of the more difficult species of houseplants.  Changes should be done slowly to avoid stress.  If houseplants are kept outside in the summer, waiting too long can see the loss of some plants with lower temperature tolerances.  Placing plants closer to the house or inside a simple greenhouse can help during the first cool nights of early fall.  Especially sensitive plants should be brought in before any threat of cool weather.  I learned this lesson the hard way with my prized Philodendron squamiferum.  Its ideal temperature range is 65-85 degrees Fahrenheit.  I had it in the basement and was planning on moving it to the first floor, but left it down there as the light was nice.  While this plant technically can tolerate temperatures in the 50s for a short duration, it got too cold for too long and it dropped all its leaves one night (it died).  As a general rule of thumb, if it is too cold for people, it will be too cold for our houseplants!

The UConn Home & Garden Education Center supports UConn Extension’s mission by providing answers you can trust with research-based information and resources. For gardening questions, contact us toll-free at (877) 486-6271, visit our website at homegarden.cahnr.uconn.edu, or reach out to your local UConn Extension center at cahnr.uconn.edu/extension/locations.

This article was published in the Hartford Courant August 2, 2025

Plants Enjoy Summer Too!

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By Dr. Matthew Lisy, UConn Adjunct Faculty 

A monstera adansonii with yellowing, curling and damaged leaves
This Monstera adansonii, that was sunburned. The damage can take weeks to fully appear, first starting as faint yellowing, then brown dead tissue (photo by M. Lisy).

A summer vacation can be beneficial for our houseplants provided that we pay attention to some abiotic (nonliving) factors.  Plants need time to adapt to new growing conditions or they can have deadly consequences.  Try and make the change as gradual as possible.  I usually wait until the end of May, where temperatures are consistently in the 70s for the highs, and no lower than 50s for the lows.   

Our plants cannot go from dim, indoor lighting to super bright full sun outside.  Any leaves subject to this will burn and die.  The best way to acclimate plants to life outdoors is to place them in the shade of a large tree for about a week, and then gradually expose them to some direct sunlight.  At first, start with only an hour or two of sun, and then add a bit more the following week until you transition them to full sun.  This is assuming that the plants in question are ones that need full sun.  Cacti and succulents can generally be transitioned to full sun (one notable exception are the forest cacti).   

Most of our houseplants are actually forest-floor species or epiphytes (these grow and live on the trunks of other trees).  Either way, those two groups of plants grow in the understory shade of a larger tree in nature, and do well there over the summer.  Some plants I saw recently for sale were called neon philodendron.  These have light green leaves (similar color to neon pothos).  The light was so intense that it bleached the leaves to a pale-yellow color, and some were turning brown.  The plants looked miserable, and the grower said she was going to move them to a shadier location.   

 I am not sure why we cannot have normal weather, but it seems we have had either too dry or too wet the last five years.  When it rains consistently, it keeps our plants in a constantly moist state, which leads to root rot.  I lost a few really nice philodendrons due to them being too moist in last summer’s constant rain.  The ideal setting would have the plants exposed to good light while under cover.  This way, the gardener can water them appropriately based on the needs of each plant.  If this is not an option, repotting and adding some extra perlite to the mix will help the pot shed the excess water.  Be sure to remove the saucer from the pots and hanging baskets while the plants are outside.  These will hold excess water and keep the plants in a constantly moist state and favor fungal infections.   

 A pot or hanging basket may only have about a gallon or two of soil at best, and will dry out quickly in the heat.  Depending on your soil type, it may be almost impossible to water enough.  Try to avoid full sun in the hottest part of the day between noon and 2:00 p.m.   

 In an exposed location, wind can rapidly desiccate, windburn, or break plants. A good friend of mine with a large houseplant collection in the Midwest had almost everything he owned blown over and damaged when a tornado swept through his town last summer.  Although he did not experience a direct hit, the winds were so bad it ruined many of his mature plants.  I told him to look at it like an unintentional propagation event.  When vining plants are grown in hanging baskets, they sometimes start to cling to the branches around them and rip in the wind.   

Hopefully this article will help plants enjoy their summer vacation.  It is a great time for plants to grow and be propagated.  Be careful of the extremes of summer, and give the plants a gentle exposure to the outdoors. 

 The UConn Home & Garden Education Center supports UConn Extension’s mission by providing answers you can trust with research-based information and resources. For gardening questions, contact us toll-free at (877) 486-6271, visit our website at homegarden.cahnr.uconn.edu, or reach out to your local UConn Extension center at cahnr.uconn.edu/extension/locations. 

This article was published in the Hartford Courant and The Westerly Sun June 21, 2025

Put an End to Blossom-End Rot: Water and Nutrient Management is Key

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By Nora Doonan, UConn Soil Science Graduate Student, Department of Plant Science & Landscape Architecture

5 ripe tomatoes
Photo by Julie-Ann Adorno, Soil Science Graduate Student, UConn Plant Science & Landscape Architecture

It can be frustrating to put time and energy into growing tomatoes, only to find that your tomatoes have developed blossom-end rot. Blossom-end rot is a physiological disorder that commonly affects tomato plants, characterized by a black, sunken spot on the fruit. This disorder is caused by insufficient calcium as a result of nutrient and water management challenges. Blossom-end rot can also affect peppers, eggplants, squash, and watermelons. In tomatoes, it is commonly seen on larger and elongated varieties, which can have a greater demand for calcium. Calcium is an essential plant nutrient that is required for proper growth, especially for the development of cell walls in the tomato fruit. When a fruiting tomato plant experiences calcium deficiency, the cell wall can collapse and show the appearance of blossom-end rot. Soil tests can reveal if your soil has sufficient levels of calcium and can determine if your soil pH is optimal for nutrient availability.  

Oftentimes, the soil is sufficient in calcium levels, but blossom-end rot still occurs. Blossom-end rot can be closely associated with soil moisture that is too wet or too dry. The soil should never dry out completely. It is important to water regularly to ensure that plants receive 1 to 2 inches of water a week. A cycle of dryness followed by overwatering is only promoting calcium deficiency in the plant. If soil is too saturated, there may be insufficient oxygen levels in the soil that can affect the roots’ ability to take up water and nutrients.  

One method of maintaining optimal soil moisture is to mulch tomato plants with an organic mulch, such as wood chips or straw, after the soil has warmed up. This will help to prevent excessive evaporation and drying of the soil. Another method is to plant tomatoes in a mound of soil that is high in organic matter or compost. Organic matter can retain soil moisture and provide adequate drainage.  

There are other factors that can affect calcium uptake by the plant, such as high concentrations of ammonium, potassium, and magnesium in the soil. This can be caused by over fertilization. Specifically, over fertilizing with nitrogen can promote excessive production of leaves in the tomato plant, which can preferentially distribute calcium to the leaves rather than the fruit.  

Calcium movement in the plant is dependent on transpiration, which is the loss of water to the atmosphere from plant leaves, stems, and flowers. Calcium is taken up through the roots and relies on water flow through the xylem for transport through the plant. This movement of water through the xylem is driven by the process of transpiration. Calcium is not redistributed from the leaves to the fruit. In addition, the overfertilization of ammonium, potassium, and magnesium can allow for competition in root uptake of calcium because they are all positive cations. Damages to roots, caused by fertilizer burns or cultivation, can also be a factor in impairing nutrient and water uptake. To prevent blossom-end rot through fertilization practices, apply fertilizer as recommended by a soil test and apply nitrogen fertilizers in the form of nitrate, rather than ammonium.   

Any affected fruits can be removed from the plant, as they will continue to drain moisture and calcium for development from other fruits. A foliar application of calcium can be made to the leaves when the fruit is young, but it is not the most effective method, since calcium in the leaves is relatively immobile. The goal is to prevent the need for foliar application through water and nutrient management across the tomato plant growth stages. Hopefully these methods will allow you to prevent blossom-end rot starting at beginning stages of growth, so that you can enjoy a bounty of beautiful, red tomatoes.  

The UConn Home & Garden Education Center supports UConn Extension’s mission by providing answers you can trust with research-based information and resources. For gardening questions, contact us toll-free at (877) 486-6271, visit our website at homegarden.cahnr.uconn.edu, or reach out to your local UConn Extension center at cahnr.uconn.edu/extension/locations. 

This article was published in the Hartford Courant June 14, 2025

Rocky Start for Rhododendron’s This Spring

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By Heather Zidack, UConn Home & Garden Education Center

Two Rhododendron shrubs. Shrub in the foreground showing leaf curl while shrub behind it looks healthy and is not displaying any signs of stress.
Rhododendrons are showing a varying degree of stress responses to winter conditions in the landscape. Photo by Heather Zidack

Rhododendrons are looking rough this spring. You’ve probably seen it in your yard or in your neighborhood. The UConn Home & Garden Education Center has been seeing an increase in the number of calls regarding injury or damage to rhododendrons.  In most cases, we are finding these reports to be winter injury. This is an environmental type of damage, caused by a perfect storm of conditions that we have seen throughout the state. So, let’s take a closer look into why this is happening.

Plants lose water through their leaves. During active growth, that water is constantly replenished from the roots. When the temperatures drop and the ground freezes in the winter, available water becomes limited. Plants have adapted to this in many ways. Dormancy is triggered by multiple factors, but water conservation is certainly one of those. Deciduous trees shed their leaves completely. Evergreens have developed various leaf adaptations to help with survival, too.

As broadleaf evergreens, rhododendrons have developed a waxy coat on their leaves to help prevent water loss. They also have a physiological mechanism to help defend themselves further. Just as you’d clasp your hands together on a cold winter day to shield them from the elements, rhododendron leaves curl themselves into cigar-shaped cylinders. The leading theory is that this happens to protect the leaves from further water loss. This natural defense mechanism has grabbed our attention this spring, since our weather patterns have lent a hand in amplifying a natural phenomenon.

At the end of last summer, CT started to see a moderate drought in much of the state. These conditions have persisted through this spring. Water availability was limited as plants went into the winter and remained limited throughout the season. Add in frozen soil and harsh winter winds and the environmental stress increased even more. When water is unavailable to the roots – through either freezing or drought conditions, plants lose their ability to return water to the living tissues. This drying out, referred to as desiccation, leads to winter injury or winter kill depending on the severity of damage. While we are finally seeing rain, these plants need time to recover and may not be ready to unfurl just yet.

Many have noted that some plants are faring better than others even within the same bed. This is also normal to some extent. It can be easy to forget that plants are living things in our landscapes. There is going to be variance in their ability to withstand environmental pressures and their recovery rates.

If you are seeing this in your rhododendrons, be patient this spring and monitor over the next month or so. With an increase of rain in the forecast, the extra hydration should help plants recover - or at least push out new growth. These shrubs will shed any leaves that are damaged beyond repair on their own. Do not prune or fertilize shrubs until the end of May to avoid further injury.  If we go a week without rain, consider watering your shrubs to help speed up recovery – but only water if the soil feels dry to the touch! If by mid-late May you are seeing absolutely no improvement, we start to consider other factors that may contribute to the plant’s health. For now, they just need a little more time.

The UConn Home & Garden Education Center supports UConn Extension’s mission by providing answers you can trust with research-based information and resources. For gardening questions, contact us toll-free at (877) 486-6271, visit our website at homegarden.cahnr.uconn.edu, or reach out to your local UConn Extension center at cahnr.uconn.edu/extension/locations.

This article was published in the Hartford Courant Apr. 12 2025