When should I plant Rhubarb in Zone 4a?

Start Rhubarb seeds indoors around Feb 24. Transplant outdoors after Apr 7. Expect first harvest around Apr 7.

What is the last frost date for Zone 4a?

The average last spring frost date for Zone 4a is May 5. The first fall frost averages Oct 1, giving a 149-day growing season.

Can I grow Rhubarb in Zone 4a?

Yes. Rhubarb needs 90 days to harvest. Zone 4a has a 149-day growing season, which is sufficient.

Growing Rhubarb in Zone 4a

Zone 4a has cold winters and a moderate growing season. Timing is key for Rhubarb in this zone. Last frost: May 5. First frost: Oct 1.

Planting Calendar

Indoor

Outdoor

Harvest

Feb 24Oct 1

Season: May 5 – Oct 1 (149 days)

Zone4a

Last FrostMay 5

First FrostOct 1

Season Length149 days

Days to Harvest90

SunFull Sun

Frost ToleranceHeavy

Spacing1/sqft (12" apart)

When to Plant Rhubarb in Zone 4a

Start Seeds Indoors: Feb 24

Start Rhubarb seeds indoors around Feb 24 (10 weeks before last frost). Optimal germination temperature: 65°F. Germinates in 7–21 days.

Transplant Outdoors: Apr 7

Transplant Rhubarb seedlings outdoors after Apr 7. Wait until soil temperature reaches 40°F. Space plants at 1/sqft (12" apart). Harden off plants for a week before moving outside.

Harvest: Apr 7

First harvest approximately Apr 7 (~365 days from transplant). Continue harvesting until first frost (Oct 1). Rhubarb can overwinter in mild climates for continued harvest.

Rhubarb in Other Zones

1a 1b 2a 2b 3a 3b 4a 4b 5a 5b 6a 6b 7a 7b 8a 8b 9a 9b 10a 10b 11a 11b 12a 12b 13a 13b

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