What to plant this week in Helena, MT
Helena gardeners are finally in the green zone, with average last frost passing on May 12 to allow aggressive transplanting of heat-lovers like Beefsteak Tomatoes and Habanero Peppers. This week marks the start of your final spring push before the October 1 freeze locks out late crops like Winter Squash and Pumpkins.
The next 7 days
Helena, MTGrowing in Helena right now
- Helena's cold snaps are unpredictable; cover newly transplanted Zinnias and Sunflowers with frost blankets if overnight temps dip toward -25°F thresholds typical for Zone 4b.
- Our clay-loam soils near the Missouri River hold moisture well but drain slowly, so ensure your Potato and Rutabaga beds have raised rows to prevent rot during wet late-May spells.
- Take advantage of our relatively low summer rainfall by pinching back Basil and Shiso now; this encourages bushier growth before the July heatwave intensifies.
- Start planning your fall harvest calendar immediately, as Garlic and Parsnips planted in spring will need protection against early October frost to mature fully.
Sow this week
No direct sowing windows open this week.
Transplant this week
Nothing is due to go out this week.
Harvest soon
50 crops- Basil
- Beefsteak Tomato
- Bell Pepper
- Borage
- Brussels Sprouts
- Bush Bean
- Cantaloupe
- Celery
- Cleome (Spider Flower)
- Cosmos
- Cowpea (Black-Eyed Pea)
- Cucumber
- Dahlia
- Edamame
- Eggplant
- Fennel
- Flour Corn
- French Marigold
- Garden Geranium (Zonal)
- Garden Verbena
- Garlic
- Habanero Pepper
- Honeydew Melon
- Jalapeño
- Lantana
- Leek
- Lima Bean
- Loofah (Luffa)
- Marconi Pepper
- Nasturtium
- Ornamental Sweet Potato Vine
- Parsnip
- Petunia
- Pole Bean
- Potato
- Pumpkin
- Rutabaga
- Scarlet Runner Bean
- Shiso (Japanese Basil)
- Summer Savory
- Sunflower
- Sweet Corn
- Thai Basil
- Tomatillo
- Vinca (Madagascar Periwinkle)
- Watermelon
- Winter Squash
- Yellow Summer Squash
- Zinnia
- Zucchini
Seasonal tips
- Finish succession planting bush beans and pole beans to extend the summer harvest window.
- Apply a thick layer of compost around root vegetables like parsnips and rutabagas as they mature.
- Deadhead spent flowers on zinnias, cosmos, and marigolds to encourage more blooms all season long.
Pest & disease watch
- Watch for aphids clustering on new growth of Pole Beans and Scarlet Runner Beans while plants are establishing roots after transplanting.
- Spider Mites often target Eggplant and Tomato foliage when humidity drops during Helena's dry, windy May days; spray with water or neem oil early.
- Root maggots can attack young Leek and Garlic seedlings if soil stays wet; use floating row covers immediately to create a physical barrier.
Watering this week
Water deeply at the soil line in the morning to prevent fungal issues on these thirsty summer crops.
Don't forget to save seeds from your favorite varieties like Beefsteak Tomato or Yellow Summer Squash before they ripen fully this week.
Helena gardening questions
3Can I plant my Zucchini and Summer Squash seeds directly into the Helena ground this week?
Yes, once soil temperatures consistently stay above 60°F, which usually coincides with our May 12 frost date. Avoid planting until then to prevent seed rot in our cool, wet spring soils.
My transplanted Tomatillos are wilting after coming out of the cold frame; is this normal?
It can be transplant shock or root disturbance, common when moving delicate crops into Helena's rocky soil. Water them deeply once and apply a 2-inch mulch layer to retain moisture while new roots establish.
What should I do with my Garlic if it gets frosty again next week?
Garlic is cold-hardy and can survive brief dips toward our minimum of -25°F, but heavy wetness combined with freezing threatens rot. Ensure your garlic beds have excellent drainage before the next storm.
Other cities in zone 4b
3See the full zone 4b guide → · Plan your Helena garden in SproutGuide →