Your June Gardening To-Do List: Pruning, Perennials & More
June is National Perennial Month, and for good reason. This is one of the busiest and most rewarding times of year in the garden. Perennials are hitting their stride, spring bloomers are winding down, and now is the window to shape, feed, and protect your plants before summer heat sets in for good.
If you’re in the St. Louis area, here’s what to put on your list this month.
Pruning & Trimming: Get It Done Before the End of June
June has a hard deadline when it comes to pruning spring-flowering trees and shrubs. If you wait too long, you risk cutting off the buds that would have given you blooms next year. The general rule: finish any pruning of spring-flowering plants before the end of the month.
Shrubs You Can Trim Now
- Boxwoods – Trim for shape anytime in June.
- Burning Bush – Clean up and shape as needed.
- Lilacs, Forsythia, Viburnums & Azaleas – Wait until after they’re done blooming, then trim and shape. Doing this now gives plants plenty of time to set new buds for next spring.
Why the deadline matters: Pruning too late in the season can remove next year’s flower buds before they ever get a chance to develop. When in doubt, get it done before July.
Perennial Care: Deadhead, Cut Back & Clean Up
Your perennials need a little attention this month to keep them looking their best and performing well through fall.
Daffodil Foliage
In mid to late June, it’s finally time to cut back daffodil foliage. The key is patience: wait until the leaves have turned completely yellow before you remove them. The foliage is still feeding the bulb until then, and cutting too early can affect next year’s blooms.
Asters
Cut asters back by about half this month. It might feel counterintuitive, but this simple step prevents flopping later in the season and encourages fuller, bushier growth. Your asters will thank you in September.
Peonies & Other Spring Perennials
As spring-blooming perennials finish their show, deadhead spent blossoms to keep plants tidy and redirect energy. This includes peonies, which benefit from having faded blooms removed promptly.
Fertilizing: A Few Important Windows Before July
June is your last good chance to fertilize trees, shrubs, and roses before the summer slowdown. Here’s what to focus on:
- Trees & Shrubs: Fertilize as needed before July 4th. After that, it’s generally best to hold off until fall.
- Roses: After the first round of blooms, give your roses a boost. A fertilizer higher in phosphorus is ideal for promoting more blooms. If you don’t have one on hand, a balanced fertilizer works fine.
Watch for Powdery Mildew
Warm days and cool nights in June create ideal conditions for powdery mildew. It shows up as a white, powdery coating on leaves and can spread quickly if left unchecked.
Keep an eye on these plants in particular:
- Roses
- Phlox
- Monarda (bee balm)
- Zinnias
- Lilacs
If you spot it, remove affected plant material right away and dispose of it in the trash, not the compost. Don’t let it sit on the plant or fall to the ground where it can spread.
Quick June Checklist
- Trim boxwoods and burning bush
- Shape lilacs, forsythia, viburnums, and azaleas after bloom
- Complete all spring-flowering tree and shrub pruning before June 30
- Cut back yellowed daffodil foliage in mid to late June
- Cut asters back by half
- Deadhead peonies and other spring perennials as blooms fade
- Fertilize roses after first bloom
- Fertilize trees and shrubs before July 4th
- Monitor for powdery mildew and remove affected growth
Need a hand keeping up with summer garden maintenance? Quiet Village Landscaping has been caring for St. Louis properties since 2001. Contact us to learn more about our maintenance programs.
