Fertilizer

Fall is a Great Time to Lime and Fertilize Lawns

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By Dawn Pettinelli, UConn Home & Garden Education Center

With the end of summer drawing near and hopefully bringing cooler temperatures and needed precipitation, now is a great time to attend to your lawn. While some of us are reducing the size of our lawns and adding native plants, in many cases lawns still serve a valuable purpose for practical uses, recreation and to set off plantings. Traditional cool season grasses like Kentucky bluegrass, fescues and rye grasses require a higher pH and more fertility than our native soils provide. Right now is the perfect time to add limestone and fertilizer, if needed. Improved soil conditions will assist lawns recovering from the heat and drought stresses of summer. Also, the cooler fall temperatures allow turfgrasses to resume active growth.

Having your soil tested before purchasing limestone and fertilizer is always a wise move. Check out the UConn Soil Testing Lab’s website or give them a call at (860) 486-4274. Many of our soils tend to be acidic with a pH of 5 or so. You might remember that the pH scales ranges from 1 to 14 with 7 being neutral and values below that acidic and above that alkaline. Cool season turf grasses prefer a soil pH in the mid 6’s. When the soil pH is too low, it reduces the amounts of nutrients that are available to turf grasses even if fertilizer has been applied, increases the solubility of toxic elements like aluminum and can cause a decrease in good root formation, contribute to thatch accumulation and affect soil microbes.

Fortunately adjusting your soil’s pH is relatively easy and affordable. Limestone can be purchased either as a ground white powder or in earth tone pelletized forms. There are two main types. Calcitic limestone consists predominantly of calcium carbonates while dolomitic limestone contains both calcium and magnesium carbonates. Usually, dolomitic limestone is more commonly found as it is mined locally and it is fine to use as magnesium is an essential nutrient.

A person pushing a spreader
Photo by dmp2024

Typically, limestone is applied at rates of 50 pounds per 1000 square feet. If the soil pH needs to be raised significantly, additional limestone can be applied either spring/fall or at 30-day intervals. Once your soil pH reaches the mid 6’s, a maintenance application of 50 pounds/1000 square feet every other year should suffice. Do keep in mind that limestone does take anywhere from 6 to 18 months to change the pH depending on environmental conditions. While some more costly products are advertised as ‘Fast Acting Lime’, studies comparing them to traditional ground or pelletized limestone are inconsistent. If using these products, just follow the instructions on the package.

Choosing a fertilizer is often a confusing task considering the vast selection available. All plants need at least 18 different elements to grow. The 3 that are most often deficient in our soils and components of most fertilizers are nitrogen (N), phosphorus (P) and potassium (K). So, the 3 numbers found on a bag or box of fertilizer, like 10-10-10 or 27-4-6 represent the percent of total nitrogen, available phosphate, and water-soluble potassium, respectively. For instance, a ten-pound box of 10-10-10 contains 10 percent or 1 pound of total nitrogen, and another 10 percent or 1 pound each of available phosphate and water-soluble potassium.

A law passed in 2013, limits the amount of phosphorus that can be applied to established lawns because it is the number one inland freshwater pollutant. Lawn maintenance fertilizers sold in Connecticut will typically have analyses like 30-0-4, 29-0-5 or 10-0-6. While phosphorus applications are prohibited on established lawns, fertilizers with phosphorus can be used when seeding, sodding or overseeding.

Fertilizers are also grouped as either those containing water-soluble nitrogen (WS) of water insoluble nitrogen (WIN). Look for a fertilizer that contains both. That way some nitrogen will be immediately available to your lawn and some will be released slowly over time. Fertilizers containing solely soluble N will produce rapid results but can easily burn if over applied and since some forms of nitrogen are readily leached from the surface soil, more frequent fertilizer applications may be necessary. No more than 1 pound of nitrogen per 1000 square feet should be applied at one time. If grass clippings are left in place then only 2 pounds of nitrogen per 1000 square feet of turf area will be needed each year. The best times to fertilize lawns are in September and in late April through the end of May. Avoid using too much nitrogen as it can lead to increased susceptibility to diseases and lower resistance to stress. If in doubt as to how much lime and fertilizer to apply, consider having your soil tested.

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 or reach out to your local UConn Extension center.

This article was published in the Hartford Courant September 20, 2025

It’s Spring! Time to Feed the Plants!

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By Dawn Pettinelli, UConn Home & Garden Education Center

Plants need nutrients to grow and develop just like we need vitamins and minerals. They get most of their nutrients dissolved in the water they take up with their roots. When we add fertilizer to the soil around our garden plants, we are adding vital plant nutrients.

Native Connecticut soils are typically low in pH and low in nutrients. Our native plants have adapted to our native soils but most of our garden plants are not from around here. Zinnias and tomatoes are from South America, bluegrass lawns and lilacs hail from Europe and rhododendrons from Asia. Our native soils may not supply the nutrients they need so it is up to us to do so.

Of course, the best way to know which nutrients and how much to add is with a soil test. April is a very busy month at the UConn Soil Nutrient Analysis Lab (www.soiltesting.cahnr.uconn.edu) but there is still time to get your soil tested before planting.

Without soil test recommendations, always follow the directions on the fertilizer package. Applying too much can injure your plants plus excessive nitrogen and phosphorus can wind up in our waterways. Before fertilizing, calculate out the square footage of your garden or lawn. You don’t need to measure exactly; you can measure a pace and then walk down the length and across the width of your gardens to get a rough estimate of area. For odd-shaped beds or lawns, break them down into more square, oval or rectangular areas and add them up.

All fertilizers come with 3 numbers on the package denoting the percent, on a dry weight basis, of nitrogen, phosphorus and potassium. Nitogen promotes green, leafy growth, phosphorus encourages fruits and roots, and potassium is for all round health and tolerance to stresses like drought, cold and disease. So, fertilizers with a higher nitrogen number would be most appropriate for turf grasses, trees and shrubs, while ones higher in phosphorus are generally used in vegetable and flower gardens.

Adding fertilizer to perennials with a watering can and a hand rake.
Fertilizer spread around a perennial. Photo by dmp2024

Whether you select a synthetic or natural organic fertilizer is a matter of personal choice. Both are beneficial to plants. For annual plantings, whether vegetable or flowers, it would be ideal to mix the fertilizer into the top 6 inches of soil. That’s where most of the roots will be so it makes sense that the nutrients they need are there too. Put down the fertilizer, as well as any limestone or other amendments shortly before planting. Long season annuals, like tomatoes, pumpkins and marigolds would appreciate a second application of fertilizer, referred to as side dressing, about 2 months after the first one.

As you are cleaning up your perennial beds and see the new shoots popping through the soil, add some fertilizer around plants and carefully scratch it in. Do the same for bulbs. It is harder to fertilize if the beds are heavily mulched. Not much fertilizer spread on top of mulch will make it to the plant roots. Rake or pull away the mulch, sprinkle some fertilizer directly to the soil around your plants and replace the mulch.

For trees and shrubs, fertilizer should be spread under the whole canopy as a healthy root system will grow at least as wide as the branches and perhaps even more so. Do your best to remove the mulch before fertilizing. Typically trees and shrubs are fertilized once a year in the spring. Once they have reached their mature size, often the fertilizer is cut down to half rate as woody plants can recycle many of the nutrients they need.

Lawns can be fertilized now but pay attention to the moisture level of the soil. With all the rain that we have been experiencing, the soil is pretty soggy in spots. Stay off wet soils as they will become compacted. Most lawns do well with just a spring and fall application of fertilizer. If the clippings are left down, they supply nutrients plus add organic matter to the soil. Be sure to set your spreader on the proper setting.

If you have questions about fertilizing or if you have any other gardening questions, contact the UConn Home & Garden Education at (877) 486-6271 or www.homegarden.cahnr,uconn.edu or your local Cooperative Extension Center.