May garden checklist
UNIVERSITY OF MINNESOTA EXTENSION - www.extension.umn.edu
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Mystery of the month
What happened to these eggplant seedlings?
The solution is at the bottom of this article.
Pests and diseases
Monitor your plants for pests, because early detection can mean less work later. Look on the underside of leaves and where leaves and branches meet.
Some signs of pest issues include discolored leaves, chewed areas, speckling on leaf blades, and sticky residue on and around the plants, among others.
Not all “pests” are an issue, and some may even be beneficial. Make sure you know what the insect is before you remove it. Learn about common Minnesota yard and garden insects.
Trees and shrubs
Prune spring-flowering shrubs after they are done blooming this month, because next year’s flower buds will form this summer and fall. If you wait and prune in winter, you will remove the flowering buds for next year!
Pruning trees and shrubs is important for healthy, resilient plants.
Flowers and other garden plants
Plant cool-season flowers in early to mid-May, like snapdragons, violas and pansies, and sweet alyssum. These plants can handle light frosts. You can also safely direct-seed cool-season vegetables into the ground once the soil is workable. Try peas, lettuce, carrots, and radishes.
Hold off on planting warm-season annuals until your area is free of frost, like tomatoes, peppers, zinnias, and sunflowers. If you do plant some frost-sensitive plants early, you may need to cover them and/or bring them indoors overnight.
When planning your vegetable garden, check the approximate dates for when it is safe to plant outside.
Houseplants
Check the last frost date for your area before you begin bringing plants outside for the year. The average last frost date is based on a hard freeze (28°F), which is much too cold for your pampered houseplants.
Most houseplants grow best when temperatures do not drop below 60°F, well above the temperatures used for determining last frost.
Lawn
Your lawn should be greening up and beginning to grow at this point. If some of the lawn succumbed to winter stresses, you may want to spread seed or lay sod to reestablish turf.
Raise your mowing height to at least 3.5 inches and begin mowing as needed when the majority of the lawn is a little over 5 inches tall. A taller mowing height will result in a deeper-rooted lawn that needs to be mowed less often, is more drought-tolerant, and is more resistant to weeds like crabgrass.
Other tasks
Remove the faded flowers from spring-flowering bulbs and fertilize the plants. Leave the leaves as long as possible so they collect sunlight and put energy into their bulbs to form next year’s flowers.
Watch our Hort Short on removing tulip flowers.
Solution to the mystery of the month
The nighttime temperatures dropped to 32°F, which is much too cold for warm-season plants, and cells in the leaves were damaged by the cold.
To prevent this from happening, wait to put warm-season plants, like eggplants, tomatoes, peppers, and cucumbers, outside until nighttime temperatures are consistently above 50°F.
If you do have plants that are prone to cold damage outside, you can bring them indoors at night and put them out after temperatures warm up mid-morning.
