Fall cleanup is important, but timing matters. Cutting perennial plants back too early can reduce winter survival and may remove food reserves that plants need for next year’s growth.
For gardeners in Kamloops and much of the Southern Interior, wait until a hard frost has blackened and collapsed foliage before cutting back most perennials. This typically occurs from late October through November, although local microclimates may vary.
General Fall Cleanup Tips
- Remove and dispose of diseased plant material rather than composting it at home.
- Municipal composting facilities reach much higher temperatures than backyard compost piles and are more likely to destroy disease spores and insect pests.
- Clean pruning tools regularly using 70% rubbing alcohol between plants to prevent spreading diseases.
- Avoid using bleach on metal pruners, as it can cause corrosion and damage.
Bearded Iris
Why Cut Back?
Old iris foliage can harbour pests and diseases. While the notorious iris borer is not a major pest in British Columbia, removing dead foliage still helps reduce overwintering insects and fungal problems.
What To Do
- Wait until after a hard frost.
- Cut foliage back to 5 to 8 cm (2 to 3 inches).
- Remove all dead leaves and garden debris around the rhizomes.
- Dispose of material in yard waste.
Spring Check
Inspect new growth for damage or signs of rot and remove affected leaves promptly.
Peonies
Why Cut Back?
Peonies can suffer from Botrytis blight and leaf blotch, especially during cool, wet springs.
What To Do
- After frost, cut herbaceous peonies to ground level.
- Remove all fallen leaves.
- Dispose of plant debris rather than composting.
Kamloops Note
Our dry climate generally reduces disease pressure compared to coastal regions, but wet springs can still trigger fungal problems.
Tree peonies are different. Leave their woody stems intact and remove only fallen leaves.
Hostas
Why Cut Back?
Dead hosta leaves create shelter for slugs and snails, which can be problematic in irrigated or shaded gardens.
What To Do
- Remove frost-damaged foliage to the crown.
- Check around crowns for slug eggs.
- Dispose of leaves in yard waste.
Spring Tip
Apply an iron-phosphate slug bait around emerging shoots if slug damage has been an issue.
Bee Balm (Monarda) and Garden Phlox
Why Cut Back?
Both are prone to powdery mildew, especially during warm periods followed by irrigation and poor air circulation.
What To Do
- Cut stems back to 2 to 5 cm (1 to 2 inches) after frost.
- Remove all infected foliage.
- Improve spacing and airflow.
Good Resistant Choices
- Bee Balm: ‘Jacob Cline’
- Phlox: ‘David’ and ‘Jeana’
These varieties perform well in many Interior BC gardens.
Hollyhocks
Why Cut Back?
Hollyhock rust commonly survives on infected leaves and stems through winter.
What To Do
- Remove and dispose of infected foliage.
- Cut stems back after frost.
- Pull nearby mallow weeds, which can also host rust.
Spring Management
Watch for rust spots early and remove affected leaves promptly.
Daylilies
Why Cut Back?
Removing old foliage helps reduce leaf streak and rust diseases.
What To Do
- Wait until frost turns foliage yellow and soft.
- Pull or cut leaves back to ground level.
- Dispose of diseased material.
Additional Tip
Inspect new plant purchases carefully before introducing them into the garden.
True Lilies (Lilium)
Why Cut Back?
Botrytis blight can overwinter on infected foliage.
What To Do
- Allow foliage to yellow naturally.
- Cut stems at ground level only after they have finished feeding the bulbs.
- Remove all leaf debris.
Kamloops Note
The lily leaf beetle, a serious pest in Eastern Canada, is currently not established in the Kamloops area, but gardeners should remain aware of any reports from BC.
Delphiniums
Why Cut Back?
Powdery mildew and bacterial leaf diseases can survive on old plant material.
What To Do
- After frost, cut stems to ground level.
- Remove fallen leaves and debris around the crown.
- Ensure winter drainage is good.
Kamloops Consideration
Good air circulation and avoiding overhead watering are especially important during hot summer weather.
Plants to Leave Standing for Winter
Not everything should be cleaned up in the fall.
Leaving healthy seed heads and stems through winter provides:
- Food for birds such as chickadees, finches, and juncos.
- Shelter for beneficial insects and native bees.
- Additional snow capture and insulation around plant crowns.
Consider leaving healthy:
- Coneflowers (Echinacea)
- Black-eyed Susans (Rudbeckia)
- Sedums
- Ornamental grasses
- Native grasses
Only remove foliage if it is clearly diseased.
Garden Rule of Thumb
Cut back diseased plants. Leave healthy plants standing whenever possible.
In our dry Interior climate, many perennials experience fewer disease issues than gardens in wetter regions. A selective cleanup approach supports pollinators, birds, and beneficial insects while still reducing disease carry-over into the next growing season.
This balanced approach creates a healthier, more wildlife-friendly garden and less work for gardeners in the spring.
