University of Illinois Extension


Sharon A. Yiesla
Unit Educator, Horticulture
Lake Unit

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Late Summer ‘Do’s and ’Don’t’s

Late summer is here, can autumn be far behind? Gardeners often find themselves wondering what gardening activities are best done at this time. Here is a list of things to get done now and some things to put off for a couple of months.


Keep up with watering. Water is always important, but especially so when the heat is on. Fruits and vegetables need water to develop their crops properly. Perennial and annual flowers will perform better with adequate water. Don’t forget the trees and shrubs. Even mature trees grow better when given supplemental water. For most plants, a good rule of thumb is one inch of water per week. Remember to water infrequently and deeply; avoid shallow watering.

Deadhead flowers. This is simply removing faded flowers. Deadheading annuals will keep them blooming throughout the whole growing season. Deadheading perennials will channel the energy that would have been spent on seed production, into root growth. When you deadhead, remember to remove the whole flower, not just the faded petals. The part that forms the seeds is usually at the base of the flower and that’s the part you need to remove.

Plant, transplant and divide perennials; plant spring flowering bulbs. As September rolls around, air temperatures will be cooling off, while soil temperatures stay warm. This makes for good planting. There will be less heat stress in newly transplanted plants and the warm soil encourages root development.


Don’t prune trees and shrubs yet. Woody plants need to slow down and prepare to harden off so they can survive winter. Pruning in late summer can stimulate growth that may not harden off properly and can be damaged by winter. If you want to do a late season pruning , wait until autumn is really here and the leaves are changing color and falling off the trees (usually around early October). Evergreens should not be pruned at the end of the season, wait until spring.

Don’t fertilize trees and shrubs. Just like pruning, fertilizing is a stimulus. It should wait until autumn is truly here. You can fertilize in autumn (very late September or early October), because the soil temperatures are still warm and the roots are actively growing.

Don’t mulch yet. Winter mulch can be very beneficial to perennials, trees and shrubs. Winter mulch helps to moderate soil temperatures and prevent freezes and thaws that can lead to soil heaving. Soil heaving can be detrimental to shallow rooted perennials. If you are going to apply mulch, wait until there have been a couple of light freezes, then apply the mulch.

August - September 2002:

"Pretty" Purple Plants Can Be Pesky
Rust Diseases on Home Lawns | Spring Bulbs
Late Summer ‘Do’s and ’Don’t’s | Fall Lawn Care

Past Issues

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