Cool-season annuals can start going in the ground

  • It's time to plant cool-season annuals, such as pansies and primulas, which can tolerate a light frost. Plant them near flowering bulbs, such as tulips.

    It's time to plant cool-season annuals, such as pansies and primulas, which can tolerate a light frost. Plant them near flowering bulbs, such as tulips. Courtesy of Chicago Botanic Garden

By Tim Johnson
Chicago Botanic Garden
Posted4/21/2019 7:00 AM

Plant cool-season annuals, such as pansies and primulas that can tolerate a light frost, to add color to your early spring garden. Other annuals sold for spring are good to use too but not as tolerant of very cold weather, so they benefit from a slightly later planting date or protection during cold nights.

You may want to consider installing your annuals a bit later if there is unusually cold weather predicted. Temperatures that drop into the low 20s can damage even the more cold-tolerant annuals, such as pansies. Temperatures that go down to 25 degrees will likely damage the flowers on pansies -- the plants should survive but their spring flower display will be severely impacted.

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These early spring annuals can be planted under bulbs to complement their flowers and extend color until summer annuals are planted in mid- to late May. Choose plants that are well developed with lots of flowers and buds.

The cool-season annuals do not have much time to develop after planting. If an exceptionally cold night with temperatures below 28 degrees is predicted, then it would be a good idea to cover your early spring annuals.

• It is time to begin spraying crabapples that are susceptible to apple scab (typically this disease affects older varieties of crabapples).

If your tree's leaves become covered with black spots and fall off in mid- to late summer, it is in need of a protective spray program, or it should be replaced with a new disease-resistant cultivar or completely different plant. Begin spraying after the buds open and treat once every seven to 10 days until the leaves are fully open (generally three treatments suffice).

Call Plant Information, (847) 835-0972, for recommended fungicides and timing for applications.

• Install bare root plant material as soon as you can after it arrives in the mail. Unpack plants and make sure the packing around the roots is moist. Store the plants in a cool place that will not freeze until they can be planted.


It is a good idea to soak the roots of trees and shrubs in water for a short period of time before planting. Do not let the roots dry out.

Prune only broken branches and roots before planting. There is no need to prune to compensate for transplant shock.

• Apply crabgrass control if you had problems with crabgrass last year. Apply to lawns in mid-April before the weeds begin to germinate. Complete this work before lilacs begin to flower.

If you did not have problems with crabgrass last year, then you probably do not need to apply crabgrass control this year.

• Tim Johnson is director of horticulture at Chicago Botanic Garden,

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