Fall in Washington brings crisp air, changing leaves, and the vibrant colors of chrysanthemums brightening our gardens. For many of us in the Pacific Northwest, these autumn jewels mark the season’s transition, but keeping their blooms looking fresh through our unpredictable weather can be challenging.
Whether you’re growing mums in containers on a Seattle balcony or in garden beds east of the Cascades, these nine techniques will help your chrysanthemums continue flowering until the first hard frost arrives.
1. Choose Late-Blooming Varieties
Garden centers throughout Washington offer numerous mum varieties, but not all bloom at the same time. Select cultivars specifically labeled as ‘late-season’ or ‘late-blooming’ for extended color well into November.
Local nurseries often carry varieties adapted to our region’s growing conditions. Ask staff about cushion mums, which naturally bloom later and tolerate cooler temperatures better than early varieties.
When shopping, look for plants with lots of tight buds rather than those already in full bloom. This simple selection trick ensures weeks of fresh flowers ahead rather than blooms that are already halfway through their show.
2. Perfect Your Pinching Technique
Pinching back mum plants early in the season creates bushier growth and more flower buds later on. For Washington gardens, continue this practice until about July 4th, then stop to allow flower buds to form.
The technique is simple but effective. Using your thumb and forefinger, pinch off about an inch from the growing tips of stems. This encourages side branches to develop, resulting in a fuller plant with many more blooms.
Resist the urge to pinch after mid-summer, as this removes the very buds that will become your fall flowers. Timing this cutoff properly leads to an explosion of blooms just when you want them most.
3. Feed With The Right Fertilizer
During the growing season, Washington gardeners should use a balanced fertilizer (like 10-10-10) to promote strong root and stem development. Come August, switch to a bloom-boosting formula higher in phosphorus.
Look for fertilizers with a middle number (phosphorus) that’s higher than the first and last numbers. Something like 5-10-5 encourages flower production without stimulating excessive leafy growth that won’t have time to mature before frost.
Apply at half-strength every two weeks rather than full-strength monthly. This gentler approach prevents fertilizer burn while still providing the nutrients needed for continuous flowering through our extended fall season.
4. Master The Watering Balance
Our Washington autumn brings unpredictable rainfall patterns. Check soil moisture regularly by inserting your finger about an inch into the soil near your mums. Water only when the top inch feels dry to prevent root rot in our often-damp conditions.
Water at the base of plants rather than overhead, especially as temperatures cool. Wet foliage in fall increases disease risk, while keeping leaves dry helps blooms stay fresh longer. Consider soaker hoses for efficient watering.
During hot, dry spells that sometimes surprise us in early fall, increase watering frequency but maintain the same volume. Consistent moisture—neither soggy nor parched—keeps flower production steady through the season.
5. Relocate Potted Mums Strategically
Container-grown chrysanthemums offer flexibility that’s perfect for Washington’s variable microclimates. During September heat waves, move pots to afternoon shade to prevent wilting and extend bloom time. When nights turn chilly in October, relocate them to south-facing walls.
Thermal mass from brick or concrete walls releases stored heat overnight, protecting your plants from early frosts. This simple relocation trick can add weeks to your display, especially in cooler areas like Bellingham or Spokane.
For apartment dwellers, balconies or patios with morning sun and afternoon shade create ideal conditions. The protection from buildings often creates a microclimate that’s several degrees warmer than open gardens.
6. Cover During Surprise Frosts
Washington’s fall weather can swing dramatically, with unexpected freezes threatening your mums. Keep old sheets, frost cloth, or lightweight blankets ready to drape over plants when temperatures dip below 32°F.
Apply covers before sunset to trap daytime warmth, and remove them promptly the next morning once temperatures rise. This prevents condensation from building up under the covering, which could damage delicate petals.
For extra protection in eastern Washington where frosts arrive earlier, place plastic milk jugs filled with warm water among your mums before covering. These act as mini heat reservoirs throughout the night, raising the ambient temperature just enough to save your blooms.
7. Deadhead With Precision
Removing spent blooms signals the plant to produce more flowers rather than seeds. In our Washington gardens, check mums twice weekly during peak bloom season, removing any flowers that have begun to fade or turn brown.
Use sharp, clean scissors or pruners rather than pulling blooms off by hand. Cut just above the first set of healthy leaves below the faded flower. This precision approach prevents damage to developing buds nearby.
During rainy periods common in western Washington, increase deadheading frequency. Wet petals deteriorate quickly and can spread botrytis (gray mold) to healthy blooms. Prompt removal keeps your display looking fresh despite our damp fall conditions.
8. Mulch To Regulate Soil Temperature
Apply a 2-inch layer of organic mulch around your mums once the weather cools in September. Pine needles, shredded leaves, or bark chips help maintain even soil temperatures despite Washington’s fluctuating fall conditions.
This insulating layer keeps roots warmer during cold snaps and cooler during unexpected warm spells. Stable root temperatures translate directly to longer-lasting blooms above ground, particularly in areas with greater temperature swings like the Columbia Basin.
Keep the mulch from touching the stems directly to prevent rot issues. Create a small donut-shaped barrier around each plant, allowing air circulation while still providing the temperature-moderating benefits that extend your chrysanthemum display.
9. Site Plants For Wind Protection
Washington’s autumn winds can damage tall mums and dry out blooms prematurely. Place or transplant chrysanthemums where they’ll receive protection from prevailing winds—often from the south or southwest in our region.
Natural windbreaks like shrubs, fences, or garden walls create ideal growing pockets. For existing plants, install temporary barriers using garden stakes and burlap on the windward side. This simple shield prevents excessive transpiration that shortens bloom life.
In particularly exposed sites like coastal gardens or eastern Washington’s open spaces, choose shorter, mounding varieties that naturally resist wind damage. Their compact growth habit helps them weather gusty days while continuing to produce fresh flowers.