Click below to listen to my 2 min. Garden Bite radio show: Cutting back perennials to control height
I have a butterfly garden on my corner. And I was told by the city a few years ago that some of my plants were too tall. While I AM on the corner, only one street really gets much traffic. So, don’t tell anyone but my plants will be tall again.
However, I can cut them back, and you can too. For instance, you may not like the flopover that can happen with tall native plants.
You can stake the plants, which I have done with black-eyed susans or cut them back. In particular those late summer plants like Asters. They can get floppy too.
When plants are 12 to 18 inches tall, you can prune them to 6 to 10 inches tall. About a third to half their size. While it seems a little risky, it’s not, the plants bounce back bushier, just like I talked about with herbs yesterday.
Choose some plants for pruning and hold back on others so you get a mixed height! Often those that are cut back will bloom heavier too!
Perennials for cutting back include:
- Agastache – Anise hyssop
- Boltonia
- Turtlehead
- Purple Coneflower
- Joe-pye weed
- Sneezeweed
- Heliopsis
- Lobelia – cardinal flower
- Monarda
- Phlox – sweet william
- Garden phlox
- Obedient plant
- Black-eyed susans
- Goldenrod
- Aster
- Spiderwort
- Vervain
- Ironweed
There are some plants you should not prune back, blanket flowers, gentian, false indigos and liatris.