According to Hal Hultgren, a URI Master Gardener who has volunteered to answer hotline questions since 2007, “as nature begins to perk up, so does the hotline.” And about half of the questions he fields at this time of year are about lawns.
His first recommendation for anyone trying to improve the health of their lawn is to get a soil test. “If you think about how wineries always talk about the soil forming the complexity of the grape, in our case the soil is the basis for everything that grows.” And different plants require different soil characteristics.
New England soils tend to be acidic, he said, which is ideal for growing blueberries and rhododendrons, but not for most lawns, vegetables and flowers. In that case, lime should be added to reduce the soil’s acidity. How much lime depends on the soil’s pH, so Hultgren suggests bringing a soil sample to the URI Outreach Center for testing. Detailed information about how to bring in a sample can be found at soil testing.
Callers also often inquire about the right time for treating their lawn to combat crabgrass and grubs. Hultgren said the time is now for preventing crabgrass – between when the forsythias bloom and the lilacs bloom. And grub preventative should be added in mid- to late-June, just before the grubs emerge as adults in July. Mow the lawn before application and water in the insecticide.
“But make sure you have a grub problem before treating your lawn for them,” he said. “Dig up a foot-square of sod and then count the number of grubs. Healthy grass can withstand up to 10 per square foot.”
When should Rhode Islanders plant their vegetables? That’s the second-most common question at this time of year. And the answer, in most cases, is not until after May 15, which is the average date of the last frost. Tender vegetable plants like tomatoes and peppers cannot survive a frost, so Hultgren says to hold off until the second half of the month. Seeds can be planted earlier for hardy plants such as snap peas and spinach.
The Rhode Island Planting Calendar can be found in the resources section of the URI Outreach Center website – Planting Calendar.
A soil test for your garden soil is also worthwhile, because it will determine what kind of amendments should be added to the soil to make it most productive. Hultgren says that everyone should add compost to the soil to provide a better “growing medium.” It helps the soil retain nutrients, moisture and air for better plant growth.
He also said that flowers and vegetables purchased from local retailers should not be planted immediately. Instead they should be “hardened off” for five to seven days by putting them outside during the day in an area protected from wind and direct sun to acclimate them to your local environment. Plants should be brought inside at night.
What else should gardeners do to get ready for the growing season? Prune winter-damaged shrubs, but not too soon. “Timing is important, so the rule of thumb is to wait until you see the new growth coming and prune down to the new growth,” Hultgren said. Most hotline questions about pruning focus on hydrangeas, which shouldn’t be pruned until early June, because this year’s blooms occur on last year’s growth, and this year’s growth hasn’t fully started until then. “So if you can live with sticks until June, it’s best to wait,” he said.
Lastly, Hultgren advises gardeners to diligently scout their plants for pest insects and diseases, especially on the underside of the leaves. If you need help identifying the problem, snap a photo of the plant or insect and email it to the hotline for identification and advice.
Lily leaf beetles, which decimate lilies, appear in May and should be picked off and killed, including adults, eggs and nymphs. Aphids, Japanese beetles and European chafers should also be picked off, and gardeners should scout at night for earwigs and Asiatic garden beetles. Later in the growing season diseases such as mold, mildew, and blights appear.
“If you think you have to spray pesticides or fungicides, find out what bugs or diseases you have before doing anything, because different pesticides or fungicides work for different insects or diseases,” Hultgren said. “And use the least environmentally harmful methods first.”
The URI gardening hotline is staffed from March through October from Monday through Thursday between 9 a.m. and 2 p.m. by URI Master Gardener volunteers trained by the University. Emails are answered year round. Call 1-800-448-1011, email firstname.lastname@example.org, or visit the URI Outreach Center at 3 East Alumni Ave., Kingston.