What to plant this week in Boulder, CO
Boulder gardeners are currently in a high-activity harvest window where your summer crops like Beefsteak tomatoes, Zucchini, and Sweet Corn need immediate picking to prevent spoilage from the city's intense afternoon sun. While no new starts can be planted yet due to lingering chill risks, it is the perfect time to sow fast-maturing seeds like Bush Beans and Yellow Summer Squash directly into the warming soil.
The next 7 days
Boulder, COGrowing in Boulder right now
- Protect young seedlings with row covers immediately after frost danger passes on April 21 to guard against sudden temperature swings common in our valley terrain.
- Amend your rocky Front Range soil heavily with compost before sowing anything this week, as Boulder's native gravelly texture struggles to retain the moisture these crops crave.
- Water deeply in the early morning rather than evening to reduce evaporation loss during our dry spring season and prevent fungal issues on leaves.
- Monitor your Brassica harvests closely; beet tops can bolt quickly once temperatures consistently climb above 70 degrees Fahrenheit.
Sow this week
7 crops- Bush Bean
- Cucumber
- French Marigold
- Nasturtium
- Okra
- Yellow Summer Squash
- Zucchini
Transplant this week
Nothing is due to go out this week.
Harvest soon
58 crops- Anaheim (New Mexico) Pepper
- Banana Pepper
- Basil
- Beefsteak Tomato
- Beet
- Bell Pepper
- Borage
- Brussels Sprouts
- Bush Bean
- Cantaloupe
- Carrot
- Cayenne Pepper
- Cleome (Spider Flower)
- Cosmos
- Cowpea (Black-Eyed Pea)
- Cucumber
- Dahlia
- Edamame
- Eggplant
- Fennel
- Flour Corn
- French Marigold
- Garden Geranium (Zonal)
- Garden Verbena
- Garlic
- Honeydew Melon
- Jalapeño
- Lantana
- Lima Bean
- Malabar Spinach
- Marconi Pepper
- Nasturtium
- Okra
- Ornamental Sweet Potato Vine
- Parsley
- Parsnip
- Petunia
- Poblano Pepper
- Pole Bean
- Potato
- Roma Tomato
- Rutabaga
- Scallion (Bunching Onion)
- Scarlet Runner Bean
- Serrano Pepper
- Shiso (Japanese Basil)
- Snapdragon
- Summer Savory
- Sunflower
- Sweet Corn
- Thai Basil
- Tomatillo
- Tomato
- Vinca (Madagascar Periwinkle)
- Watermelon
- Yellow Summer Squash
- Zinnia
- Zucchini
Seasonal tips
- Succession sow bush beans every two weeks for a continuous harvest throughout summer.
- Mulch around established tomato and pepper plants to retain moisture as soil temperatures rise.
- Prune dead or diseased foliage from Brassicas like Brussels Sprouts and Kale to improve air circulation.
Pest & disease watch
- Aphid colonies are exploding on newly transplanted peppers and tomatoes, requiring early intervention with insecticidal soap or strong water sprays.
- Cutworms remain active in our loose topsoil this week, chewing the stems of young beans and squash right at ground level before they establish.
- Powdery mildew is beginning to appear on Cucumbers and Squash due to fluctuating humidity levels between our dry mornings and humid nights.
Watering this week
Water deeply in the morning to encourage strong root growth while minimizing fungal disease risk.
Pinch back the tips of young Bush Bean plants if they are leggy to encourage bushier, more productive growth.
Boulder gardening questions
3Can I finally move my Tomato and Pepper plants out from the cold frame?
Yes, provided there is no threat of frost after April 21, you can transplant these heat-loving crops into prepared beds today. Ensure the soil has warmed to at least 60 degrees by sticking a finger in before placing roots.
My Zucchini plants are producing but look wilted in the mid-afternoon; what is causing this?
This is likely 'midday wilt' common in Boulder's exposed valley spots, caused by rapid water loss during our strong solar radiation. Water deeply at dawn and apply a thick layer of mulch to keep root zones cool and moist.
Should I start sowing Okra seeds now even though it feels chilly?
Absolutely not; Okra is heat-intensive and will rot in the ground until late April or early May when soils are consistently warm. Wait for that window, then sow directly into your garden rows for best success.
Other cities in zone 6a
12See the full zone 6a guide → · Plan your Boulder garden in SproutGuide →