Summer

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

Favorite Summer Plants For Hummingbirds

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By Pamm Cooper, UConn Home and Garden Education Center  

Every spring I make a list of the plants that hummingbirds visited the   most the year before, and then my search at garden centers and nurseries begins in earnest. The plants I look for are the ones that not only hummingbirds seem to benefit from the most, but also the ones that bloom the longest. I also select the plants whose flowers I enjoy as well.  

Although annuals generally have the longest bloom time, there are some perennial ornamentals that are very attractive to hummingbirds and are worth considering for a garden or a landscape. Including a small group of these plants would be a great benefit to hummingbirds as they visit your property.  

Obedient plants, Physostegia virginiana, can bloom from early June through September. These drought tolerant perennials may get 3 feet tall and some will slowly spread. If that trait is a problem, The ‘Manners’ series such as the white ‘Miss Manners’ obedient plants are not spreaders. The flowers are also attractive to butterflies, especially tiger swallowtails, and pollinators.  

Native swamp milkweed, Asclepias incarnata, is also visited by hummingbirds. This plant likes moister soils than most milkweed, and mine is planted near a birdbath that gets emptied frequently to add fresh water. This milkweed, along with butterfly weed A. tuberosa, can be deadheaded to promote rebloom.  

Hyssops, Agastache spp., are also a favorite of hummingbirds, and most have a long bloom period, some starting in late spring. The ‘Kudos’ series with small flowers that are yellow, pink or orange are the ones visited the most by hummingbirds on my property. Another favorite is ‘Boa’, which has larger flower spikes lasting a good three months. Deadheading all will prolong bloom time.  

Annual flowering plants that are a favorite of hummingbirds include Salvias, cardinal climber, Fuschias, Lantanas and Cupheas. All are easy to grow, and all but the cardinal vine can be used in containers, hangers and window boxes.  

The cardinal climber, Ipomena x multifida, is an attractive, fast-growing annual vine that has small, brilliant red trumpet- like flowers. You can save seeds from this plant and use them next year. One plant can grow to fill a large trellis, and you may need to corral it in if it starts reaching out for nearby plants.  

Of the Cupheas, the ones most visited, in my experience, are the large firecracker plant, C. vermillionaire, and the smaller one, C. schumannii, also called the orange cigar plant. The former is superior, with a compact, mounding habit and continuous bloom of orange tubular flowers until frost. If the smaller cigar plant is planted directly in the garden, give it some room as it sprawls somewhat.  

Purple flowers on a dark purple upright stem.
Black and Blue Salvia. Photo by Pamm Cooper, UConn Home & Garden Education Center

Annual Salvias like the “Rockin’ series, the ‘Black and Blue’,  ‘Roman Red’ and the ‘Hot Lips’ salvias are the ones I always have in my containers or plant directly in the ground in spaces I leave for them. I would not venture to guess which ones hummingbird prefer, as they visit all of these throughout the day.  

There are a couple of shrubs that I learned by chance observance are favorites of hummingbirds. These are Weigelas, and butterfly bushes, Buddleia davidii. There are Weigelas that bloom only in the spring, some that bloom in spring and then again later in the summer through fall, like the ‘Sonic Blooms’, and some that bloom throughout the year, like ‘Crimson Kisses’ and ‘ Peach Kisses’. The last two are smaller shrubs which have a rounded habit.  

The plants I have included in this brief article are only a small example of plants that the average gardener can include on their property in gardens or containers of some type. I will mention that while I do have a hummingbird feeder, the hummers I see are favoring actual flowers over that source of food. Downy woodpeckers and orioles do visit the feeder instead, so it is useful to them, I guess. I may start calling it my downy feeder, at least during the summer. 

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 July 26, 2025

It’s Not Too Late! Plant Now for Fall Harvests

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By Heather Zidack, UConn Home & Garden Education Center

Squash seedling with first true leaves mulched with straw.
A young squash seedling planted in time for the fall harvest! Photo by Heather Zidack, UConn Home & Garden Education Center

Gardeners have had a broad range of experiences with their vegetable gardens this season. Some planted early in May with the warm weather, which was followed by a cold front that meant covering plants, or keeping them in pots longer than you had planned. For others, a pattern of cool, rainy spring weekends delayed planting! Cornell even sent out a reminder to residents to watch for tractors on the roads a little later this season as farmers, too, were scrambling to adjust in upstate New York. Thankfully, there is still plenty of growing season left for us to shift our practices and still have a bountiful harvest from our home gardens.

There are roughly 100 days left of the growing season until the first predicted frost date, according to the farmers’ almanac. That means you have an opportunity to still plant your dream vegetable garden! Look at the “days to maturity” to determine if planting now makes sense. Many summer crops, like zucchini, cucumbers, and even some types of winter squash have much shorter days to maturity and can be started from seed right in the warm, summer soil.

Have a type of bean, radish or leafy green you love, but can’t process bushels at a time? Plant every couple of weeks this month for a staggered harvest to enjoy your favorites for an even longer period at a more manageable volume!

Do you plan to harvest garlic this month? Be ready to follow up with a short-term crop like leafy greens, beets, carrots, or even some types of corn!

The practice of succession planting gives gardeners a chance to extend the garden season and promotes soil health by keeping your garden beds active. Rotating crops in this fashion reduces the risks of soil erosion, weed overgrowth, and nutrient depletion, when done correctly.

When setting up a succession or rotation schedule, consider what has been in the bed previously and how those plantings might interact. Determine the nutrient needs of the plants you are considering. You want to be sure you are not planting one heavy feeder right after another as this may mean you need to provide more nutritional support than you planned for. Instead, opt for plants that feed on different nutrients, or better still, plants that help to reintroduce nutrients into the soil.

Succession planting and crop rotation not only benefit the garden beds that have been put on the back burner as we’ve tried to find time between the rain and temperature swings, but it may also benefit those who have a history of battling with garden pests. Planting later in the season may help prevent or minimize damage from many single generation pests, like the Squash Vine Borer or the Four-Lined Plant Bug.

Many Cole crops (those in the brassica family) and cool season crops can be started from seed now in preparation for fall planting. However, it may be best to start these indoors instead of directly sowing in the ground. Temperatures over 85 may cause delayed germination or bolting too early once those plants pop out of the soil. Starting them indoors gives you a little more control over the temperature. Otherwise, search for heat tolerant varieties for better results.

If you want a rest from the care of vegetable gardening and harvesting, consider planting annuals. There are many varieties of marigold, cosmos, zinnia, and some other beautiful cut flower varieties that could happily take up some space and lend their services to some late season table arrangements for you!

There’s a lot to still do if you want a bountiful fall harvest, and there are a lot of considerations to make when planning what to plant next. Do your research with cooperative extension or land-grant university resources for science-backed information to guide you in your next steps. And remember, we’re here at the Home & Garden Education Center to help you make sense of it all!

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 July 12, 2025

Hyped for Hydrangeas

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Nick Goltz, DPM, UConn Home & Garden Education Center, UConn Plant Diagnostic Lab 

When I moved to Connecticut in July of 2021, I remember driving through neighborhoods looking for somewhere I might eventually want to live and being struck by the beautifully-landscaped yards that each home seemed to showcase. I particularly remember being impressed by the tidy hedges of hydrangea, filled with lush globes of blue, pink and purple flowers. Can you think of a flower more emblematic of breezy, long summer days by New England coast than the hydrangea? I’ll wait. 

Hydrangeas are a fascinating group of perennial plants with some unique quirks that make them a fun addition for the home garden. The genus is native to Asia and North America, but the species grown most commonly around the world, Hydrangea macrophylla, is native to Japan and has been bred extensively for hundreds of years, resulting in many cultivars. They are also bred with other species to help select for cold tolerance or inflorescence (flower cluster) shape.  

Hydrangea macrophylla are commonly known as “bigleaf hydrangea”, but may also be called “lacecap” or “mophead” hydrangea, depending on the shape of the cultivar’s inflorescence. While many species of hydrangeas have white flowers, bigleaf hydrangeas are prized for their beautiful inflorescences that act as a natural pH indicator of the soil the plants grow in. The petals of flowers will change depending on how basic or acidic the soil is. Flowers will be blue, indigo, or deep purple in acidic soils with a pH of 5.5 or less. Plants gown in a slightly acidic soil with a pH between 5.5 and 6.5 will have a mix of purple hues. Hydrangeas grown in neutral to basic soils with a pH greater than 6.5 (especially 7 and up) will generally have fuchsia to pink-colored flowers. Many gardeners will amend the soil of their hydrangea beds from year to year to achieve the color that they hope for.  

Many folks know of the color-changing capabilities of hydrangeas, but keep reading for a few tips on how to properly care for them beyond adjusting soil pH. Hydrangeas prefer moist, well-draining soil and a sheltered spot with partial shade. Some cultivars tolerate full sun well, but must be watered consistently to look their best. Hydrangeas do not grow exceptionally large and are considered “low fire risk”, so are a better choice for planting near the home. 

A small hydrangea with both purple and pink blooms
This ‘Summer Crush’ hydrangea near my house will have purple blooms in acidic soils and fuchsia blooms with basic soils. Because both colors are appearing, I’m guessing this soil must have a pH between 5.5 and 6.5!

There’s a reason why coastal New England towns seem to be filled with hydrangeas while interior towns, particularly for our friends in Vermont, western Massachusetts, Maine, and New Hampshire, have fewer. Bigleaf hydrangeas can tolerate cold temperatures, but only to an extent. Depending on the cultivar, bigleaf hydrangeas grow best from zones 6 to 8. Most cultivars will survive zone 5 winters, but might not flower well without protection – harsh winter temperatures, especially when paired with low snow cover, can kill flower buds.  

Flower buds form on old growth for most cultivars of bigleaf hydrangea. Because of this, many folks will accidentally prune away flower buds in winter, resulting in poor flower production come summer. For this reason, it’s important to never prune bigleaf hydrangea in fall, winter, or spring. Only prune away the bare stems from the previous year when you see that no new growth is being produced from them, or in summer when collecting flowers for the vase on your kitchen table!  

 If you find the twiggy winter appearance unsightly and can’t help but prune, if you struggle with deer feeding, or if you live in an area with common late spring frosts, consider planting a “reblooming” bigleaf hydrangea. There are a few cultivars, such as ‘Endless Summer’ and sports, that will produce flower buds on old growth and (usually) a second flush on new growth. Alternatively, you could plant other species of hydrangeas, such as smooth hydrangea (Hydrangea arborescens), or panicle hydrangea (Hydrangea paniculata), which tend to be a little more cold-hardy, or oakleaf hydrangea (Hydrangea quercifolia), if you’re looking for a hydrangea for an area with very hot summers.  

If you have questions about growing hydrangeas, or any other gardening topic, call the UConn Home & Garden Education Center (toll-free) at (877) 486-6271. You can also email us at ladybug@uconn.edu, visit our website, www.homegarden.cahnr.uconn.edu, or visit your local UConn Cooperative Extension center.  

 

This article was published in the Hartford Courant and The Westerly Sun July 5, 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