Montana planting calendar

When to plant rhubarb in Montana — sow, transplant & harvest dates

Montana is mostly USDA zone 4b (range 3a-6a). Dates below are derived from rhubarb's frost tolerance and Montana's frost window — not generic national averages.

Rhubarb planting timetable for Montana

Stage	When in Montana	Anchor
Direct-sow outside	early May (May 4)	21 days before the last frost (late May)
First harvest (estimate)	early November (November 2)	~547 days from direct sow

Dates are state-wide averages for the dominant zone. Local microclimates — elevation, urban heat, coastal moderation — can shift the window by 1-2 weeks. Use the frost-date calculator for a date tuned to your town.

Why Montana's climate shifts the rhubarb dates

Montana's last spring frost averages late May and first fall frost mid-September, which sets the whole planting clock. Montana is a cold, short-season state with big elevation effects. Western valleys are milder than the high plains and mountain basins. Wait for warm soil — rhubarb stall in cold ground even after the air warms, so don't rush them out.

Rhubarb is planted as divisions or crowns in early spring while the soil is still cool, 2-3 weeks before the last frost; it is extremely cold-hardy and actually requires winter chilling to break dormancy (reliably hardy to zone 3, marginal in zones 9-10 where inadequate chilling reduces vigour). Do not harvest in year one; take only 2-3 stalks per plant in year two; harvest freely from year three onward, always leaving at least 3-4 strong stalks per crown. Never eat the leaves — rhubarb foliage contains toxic oxalates at harmful concentrations.

Frost-risk note

Don't plant before late May — a hard freeze can still set young plants back. In the high mountain valleys and northern plains (zone 3a) the safe date runs a week or two later.

Regional variation within Montana

the high mountain valleys and northern plains (zone 3a) runs roughly 1-2 weeks behind the state average; the lower western valleys near Missoula (zone 6a) can plant 1-2 weeks earlier.

Billings — USDA zone 5a
Missoula — USDA zone 5b
Bozeman — USDA zone 5a
Great Falls — USDA zone 4b
Kalispell — USDA zone 5a

What else to plant in Montana around then

Pair the post-frost slot with other warm-season crops — peppers, beans, squash, and cucumbers.

Quick-grow guide

Sun: Full sun — 6+ hours direct (tolerates light afternoon shade in hot zones).
Soil temperature for germination: Soil 4-10 °C (40-50 °F) at crown planting.
Spacing: 36-48 inches (90-120 cm) between plants.
Days to harvest: ~547 days from planting out.

Frequently asked questions

When is the best time to plant rhubarb in Montana?

In Montana (mostly USDA zone 4b), direct-sow rhubarb early May (before the last frost, late May), and harvest from early November. Rhubarb are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

What USDA zone is Montana?

Most of Montana sits in USDA hardiness zone 4b, with the state spanning roughly 3a-6a from the high mountain valleys and northern plains (zone 3a) to the lower western valleys near Missoula (zone 6a). The last spring frost averages late May and the first fall frost mid-September.

Can you grow rhubarb in Montana?

Yes. Montana's dominant zone 4b supports rhubarb — the key is timing. Rhubarb are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

Does the planting date change across Montana?

the high mountain valleys and northern plains (zone 3a) runs roughly 1-2 weeks behind the state average; the lower western valleys near Missoula (zone 6a) can plant 1-2 weeks earlier.

What else can I plant in Montana around the same time?

Pair the post-frost slot with other warm-season crops — peppers, beans, squash, and cucumbers.

Source and methodology

State zone spans from the USDA Plant Hardiness Zone Map (2023); frost-date averages from NOAA Climate Data Online. Hot-state two-season timing cross-checked against the UF/IFAS Florida Gardening Calendar and the University of Arizona Cooperative Extension planting calendar. Curated by the Growli editorial team.