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Succession Planting Calculator — Continuous Harvest
Plan sowing intervals for a continuous harvest throughout the season.
Pick a quick-maturing crop — salads, radish and spinach gain most from staggered sowing; slower crops like carrot benefit less.
Length of harvest season you want supply for — e.g. 20 weeks covers March to August.
How many plants or modules you want ready per batch — e.g. a short row or quarter-tray of lettuce.
Scale the seed-to-harvest time for your variety/site (1.0 = default). Higher = slower-maturing, pulling the last safe sow date earlier in the year.
How We Calculate This
The sowing interval follows RHS Successional Sowing advice — small batches every 2-3 weeks for a continuous supply (faster croppers like radish and beetroot at the 2-week end). Total sowings = Desired harvest weeks ÷ Sowing interval, rounded up.
Total plants = Total sowings × Plants per sowing batch.
Last sow date is the crop's maturity time counted back from the typical UK first-frost window (~mid-October), so the final batch ripens in time. Approximate seed-to-harvest times used: lettuce 8, radish 4, spinach 6, rocket 4, spring onion 10, beetroot 10, carrot 12, peas 12 weeks. Use the Maturity Time Factor to fine-tune for your variety and site.
Frequently Asked Questions
Sowing small batches of the same crop at regular intervals, so plants reach harvest at different times, giving a continuous supply rather than a glut.
Quick-maturing crops: lettuce, radish, rocket, spinach, spring onions, beetroot. These have short harvest windows so benefit most from staggered sowings.
Every 2-4 weeks for most salad crops. Match the interval to the harvest window — sow again when the previous batch starts producing.
Allow enough time for the last sowing to mature before first frosts (typically mid-October in the UK). Count back the crop maturity time.
Lettuce, radishes, spring onions, and salad leaves give the best returns from succession sowing. Sow every 2-3 weeks from March to August for continuous harvest.
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Last updated: February 2026
All calculations are estimates based on standard gardening guidelines. Results may vary with soil conditions, climate, and plant varieties.