Beware the false promise of early May heat | The Complete Home Gardener

Published 12:00 pm Wednesday, May 6, 2026

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The first week of May is usually a call for May Day alert.

Danger awaits as gardeners think that the first week of May is the green light and go message to plant out everything into the garden. Not so fast! A few warm and sunny days the start of May does not mean we don’t have chilly nights ahead.

There are a few heat-loving plants that will suffer if the temps drop in a week or so. You can safely set out most hanging baskets, bedding plants, many vegetable starts and keep on planting trees, shrubs, roses and berries.

It is these triplets of temperature trauma to watch out for this next week. If you have already planted these three, make an effort to cover them with a sheet or bring them under cover close to the house at night.

Top Three Plants to keep indoors until late May – or June:

TOMATOES

Yes, you see tomato plants for sale and yes, some gardeners have a nice warm protected spot for their chill- sensitive tomato plants, but for most people, it pays to wait until late May or even June before leaving your tomato plants unprotected overnight.

When it comes to tomatoes, they are so in tune to chilly nights that even a dip to below forty degrees can stunt their growth as they pout and go dormant from even one cool night.

Purple leaves on tomatoes are a sign of distress

The most common signal that you jumped the gun and shot down the chances of an early harvest are tomato leaves that show a purple hue to their leaves. This is your reminder to cover those plants at night and hope for more sunny days.

BASIL

Bountiful basil plants grow in the hot and dry Mediterranean. If you want beautiful basil in Western Washington, just wait. You can keep potted basil plants indoors until June and they will reward you with fast growth once they are set free outdoors in June.

Dirt Cheap Tip: Look for potted basil plants at the grocery store. Then take the pot home, dump out the plants and repot them into separate pots or divide them up and plant directly into the ground once the soil is warm. This means waiting until June when the nights are no longer chilly. Basil will not turn purple like a tomato but it will let you know how upsetting it is to become chilled on a cool May night. A chilly basil will stop growing, lose lower leaves and might even go limp from the shocking cold.

COLEUS

Colorful and carefree as a summer pot plant, coleus are the heart breakers of the garden center during the month of May. You bring home a beauty of a plant, add it to your container garden or bedding plants scheme (so many colors!) and then watch as the coleus drops lower leaves, wilts and then slowly melts into the soil. Coleus death is most often caused by the young plants into cold soil. They fare better in warmer potting soil found in container gardens. Buying coleus plants now is fine – just make sure they have a warm and protected spot for the next few weeks.

Coleus Houseplant Tip

Solve your yearning for the most colorful coleus by bringing home these beautiful foliage plants and enjoying them as houseplants until after Father’s Day in June.

Marianne Binetti has a degree in horticulture from Washington State University and is the author of “Easy Answers for Great Gardens” and several other books. For answers to gardening questions, visit plantersplace.com and click “As The Expert”. Copyright for this column owned by Marianne Binetti. For more gardening information, she can be reached at her website, www.binettigarden.com.