Now
17°C · Partly cloudy
Today
18° / 4°
Soil 6 cm
13°C
First frost
~19 days (Sep 27)
Gardening in Bozeman
AI field guide · refreshed weeklyBozeman Garden Guide: September 8–14, 2026
You're in zone 4b with 19 days until the average first frost (September 27). Soil at 13°C is cool but workable for cool-season crops. Spring frost was June 7, so you've had 93 frost-free days—enough for most annuals to finish, but tender plants need protection soon. Expect hard freeze risk by late September; plan accordingly.
Sow outdoors now
Spinach (Bloomsdale, Space or Tyee)
Direct-sow now for fall harvest before frost. Germinates well at 13°C soil; ready in 40–50 days if frost holds off.
Arugula (Roquette)
Fast-growing (30–40 days); sow thickly in rows or broadcast. Tolerates light frost and tastes better after a chill.
Radish (Cherry Belle, French Breakfast)
Matures in 25–30 days at this temperature. Sow every 10 days for succession; last sowing by mid-September.
Mâche (Corn Salad)
Cold-hardy winter green; sow now for October–November harvest. Germinates slowly but thrives as temps drop.
Garlic (German Extra Hardy, Chesnok Red)
Plant cloves 5 cm (2 in) deep, 15 cm (6 in) apart, by late September. Needs winter chill; mulch after ground freezes.
Start indoors now
Kale (Winterbor, Lacinato)
Start seeds indoors now; transplant to garden in 3–4 weeks for late-fall harvest. Improves flavor after frost.
Cabbage (Early Jersey Wakefield, Red Acre)
Sow indoors for transplant in 4 weeks; needs 70–100 days to head. Aim for harvest before hard freeze.
Broccoli (Arcadia, Belstar)
Start now for transplant by late September. Prefers cool weather; heads form as temps drop toward frost.
Harvest now
Tomatoes (all varieties)
Pick all remaining fruit, including green ones; ripen indoors or use for salsa. Frost will kill plants within 2–3 weeks.
Peppers (sweet and hot)
Harvest mature peppers; immature ones won't ripen before frost. Bring potted plants indoors if you want to extend season.
Beans (bush and pole)
Pick pods regularly to encourage final flushes. First frost will end production; pull plants and compost.
Summer squash and zucchini
Harvest daily; frost will kill vines. Pull plants once production slows; winter squash can stay in ground until first hard frost.
Tasks this week
- Stop fertilizing perennials and shrubs now to harden them for winter.
- Cut back dead perennial foliage only after hard frost; leave standing stems for winter structure and wildlife.
- Mulch around trees and shrubs with 5–8 cm (2–3 in) of compost or aged bark; keep mulch 10 cm (4 in) away from trunks.
- Drain and store garden hoses; shut off outdoor water if you haven't already.
- Scout for aphids and spider mites on remaining greens; spray with neem oil or insecticidal soap if needed.
Watch out for
- Frost can arrive any night after September 20; cover tender plants with row cloth or cloches on clear, calm nights.
- Dry conditions (0 mm rain forecast) mean fall-planted seeds and transplants need consistent watering until soil freezes.
- High winds (up to 39 km/h by September 13) can topple tall plants and dry soil quickly—stake or tie down as needed.
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