Your Complete Care Checklist for Beating the Summer Heat
St. Louis summers don’t play around. Once temperatures climb into the 90s, your garden needs a different approach than it did in May or June. Whether you’re maintaining your own landscape or just want to know what your lawn care crew should be doing this month, here’s what July calls for in the St. Louis garden.
Hold Off on Trimming Boxwoods in Extreme Heat
It’s tempting to keep everything tidy, but pruning boxwoods when temperatures sit in the 90s puts unnecessary stress on the plant right when it can least afford it. The same goes for spring-flowering shrubs like azaleas and lilacs. These set next year’s flower buds shortly after they bloom, so a midsummer trim now means fewer blooms next spring.
If you’ve got yews or burning bush that are looking a little wild, a light trim is fine this time of year. Just save the heavier shaping for cooler weather.
Clean Up Daffodil Foliage
By July, daffodil leaves have done their job of feeding the bulb for next year and are ready to go. Cut back any foliage that’s turned yellow or fully died back. Leaving it in place any longer doesn’t help the bulb and just makes your beds look unkempt.
Cut Back Asters Before Mid-July
If you want bushier asters with sturdier stems that won’t flop over later in the season, now’s the time to cut them back by about half. This is a hard deadline, though: don’t cut back asters after mid-July, or you’ll be removing the buds they need to bloom in fall.
Keep Deadheading Perennials
This is the month deadheading really earns its keep. As perennial blooms fade, snip them off to keep plants looking clean and to encourage another round of flowers. The general rule: cut back to where the flower stem meets the rest of the plant, rather than leaving a stub behind.
Watch for Powdery Mildew
St. Louis humidity is the perfect breeding ground for powdery mildew, and it loves roses, phlox, monarda (bee balm), zinnias, and lilacs. Look for a white or gray dusty coating on leaves. If you spot it, remove the affected foliage and dispose of it away from the rest of your plants so spores don’t spread.
Fertilize Stressed Annuals
Heat and humidity take a toll on annuals, and by midsummer many start to look tired or leggy. An application of Osmocote can give them the boost they need to keep performing through August. Pair it with a round of deadheading so the plant is putting its energy into new growth instead of spent blooms.
Divide Bearded Irises If Needed
July is a workable window for dividing bearded irises, though most varieties only need this every three to five years. If your irises are crowded or blooming less than they used to, division can help. Otherwise, there’s no need to disturb them just because it’s an option this month.
Why July Maintenance Matters
Skipping these small midsummer steps is one of the most common reasons St. Louis landscapes look worn out by August. A little attention now, especially around deadheading and disease control, keeps your garden blooming through the rest of summer instead of fizzling out early.
Quick July Checklist for St. Louis Gardens
- Skip pruning boxwoods, azaleas, and lilacs during 90-degree heat
- Cut back dead/yellowed daffodil foliage
- Trim asters by half before mid-July (not after)
- Deadhead perennials regularly
- Check roses, phlox, monarda, zinnias, and lilacs for powdery mildew
- Feed stressed annuals with Osmocote
- Divide bearded irises only if overdue or requested
Need help keeping your landscape on track this summer?
Quiet Village Landscaping has been caring for St. Louis-area lawns and gardens for over 25 years. Fill out the brief form below to learn more about our garden maintenance program.
