When to Plant Brussels Sprouts in Washington (2026 Guide)
Growing Brussels sprouts in Washington can be a rewarding endeavor, especially with their ability to enhance in flavor after frosts. These cool-season crops, which thrive in the cooler temperatures of fall and winter, require careful planning and attention over their lengthy growing season. The median last spring frost dates in many parts of Washington, such as April 9 in Zone 6b, shape the best planting strategies for successful harvests.
Washington's diverse climate zones mean that gardeners need to adjust their planting schedules accordingly. For example, in Zone 6a, the last frost is later, occurring around April 20, allowing for a slightly different timing in seed starting and transplanting outdoors. Properly timing your indoor starts and outdoor transplants can lead to a bountiful harvest while avoiding the risks of unexpected frosts.
Understanding the best times for indoor seed starting, outdoor transplanting, and harvesting can dramatically influence the success of your Brussels sprouts. With harvests ranging from late October through early winter, it’s important to consider the first fall frost date of October 26 in Zone 6b and other dates specific to your region, ensuring that you can enjoy the sweetest sprouts during the holiday season.
Planting Schedule by USDA Zone in Washington
| Zone | Indoor start | Transplant out | Direct sow | Harvest |
|---|---|---|---|---|
| Zone 6b | Start May 1 – May 15, ~6–8 weeks before April 9 | Transplant outdoors May 15 – May 31, after the last frost | Direct sow June 1 – June 15, after the last frost | Harvest October 1 – November 15, after exposure to several frosts |
| Zone 6a | Start April 20 – May 5, ~6–8 weeks before April 20 | Transplant outdoors May 25 – June 10, after the last frost | Direct sow June 10 – June 20, after the last frost | Harvest September 25 – November 15, after several frosts |
| Zone 5b | Start March 1 – March 15, ~6–8 weeks before May 6 | Transplant outdoors May 20 – June 5, after the last frost | Direct sow June 5 – June 15, after the last frost | Harvest September 1 – October 15, well after initial frosts |
Brussels Sprouts Planting Windows in Washington
- Indoor start: Start Brussels sprouts indoors between May 1 and May 15 for optimal growth.
- Transplant outdoors: Transplant your seedlings outdoors from May 15 to May 31 for the best results in Washington.
- Harvest: Plan to harvest your Brussels sprouts from October 1 to November 15 to enjoy the sweetest flavor.
Common Mistakes Growing Brussels Sprouts in Washington
- One common mistake Washington gardeners make is planting Brussels sprouts too late in the season, especially in Zone 5b, where frost comes as late as May 6. Adjust your planting schedule to account for the risk of late spring frosts.
- Failing to properly water during the dry spells that might hit Washington's summer can lead to stressed plants. Brussels sprouts require consistent moisture, especially during their early growth period, to thrive and develop healthy sprouts.
- Washington's coastal humidity can foster disease, particularly if plants are overcrowded. Ensure good air circulation around your Brussels sprouts by spacing them adequately and removing any yellowing leaves as they develop.
- Many new gardeners in Washington overlook the importance of nitrogen-rich fertilizers early in the season. Consistently feeding your Brussels sprouts every three to four weeks will help them grow to their full potential.
- The heat waves that can occur in Washington can be detrimental to the development of Brussels sprouts. While these plants prefer cooler temperatures, ensuring their fertility and water needs are catered to during these hotter periods will mitigate the heat's effects.
Frequently Asked Questions
What if I'm in a cold pocket of Washington?
Cold pockets can lead to unexpected late frosts, so be cautious about your planting dates. Use the last frost date for your specific zone to adjust your schedule and consider starting seeds indoors to get a head start.
Can I still plant Brussels sprouts in May?
Yes, you can plant Brussels sprouts in May, but it's essential to ensure you do so after the last frost for your zone. If you’re in Zone 6b, aim for transplanting by May 15 to guarantee a successful harvest.
How can I tell when to harvest Brussels sprouts?
Harvest Brussels sprouts when they're firm and a decent size, typically from October 1 to November 15. Allowing them to experience multiple frosts can enhance their sweetness, so don’t rush the harvest.
Do Brussels sprouts need a lot of sun?
Brussels sprouts thrive best in full sun, although they can tolerate partial shade. Aim for a space that receives at least six hours of sunlight per day to promote healthy growth and sprout development.
Should I prune my Brussels sprouts?
Pruning is beneficial for Brussels sprouts. Remove the top growing tip 4-6 weeks before your first frost to help focus energy on sprout development. This will result in larger and more uniform sprouts.
Keep Learning
City guides in Washington
Other crops in Washington
Typical fall sowing window for Brussels Sprouts in Washington: August 23 – August 23.