Seed harvest date calculator

What this calculator does

After a plant flowers, seed takes a set span of weeks to ripen, and that span differs by crop. Count forward from the flowering date and you get an approximate window for when to start checking for ripe seed. The tool uses typical figures, but the plant is the real authority: seed is ready when it looks and feels ready, not when the calendar says so.

When to use it

• Planning when to watch a crop for ripe seed.
• Working out whether seed will finish before cold or wet weather arrives.
• Timing collection so pods are gathered before they scatter.

How to use it

1. Note the flowering date for the plants you want to save from.
2. Pick the crop for a typical number of days, or enter your own from experience.
3. Watch from the calculated date, checking pods, heads or fruits every few days.

Worked example

Tomatoes that flowered around 1 July take roughly 60 days to seed, putting the estimate near the end of August. In practice you judge by the fruit: seed is ready when the tomato is fully ripe and slightly past eating, so it can be fermented and cleaned.

Typical days from flowering to seed

Weather speeds this up or slows it down. Warm, dry spells ripen seed faster; cool, wet ones delay it.

Limitations

• It is an estimate. Varieties and conditions shift the number of days considerably.
• Seed ripens unevenly. On the same plant, some pods or fruits are ready before others.
• Do not wait too long. Dry seed scatters; check often as the date approaches.

Frequently asked questions

Related guides

• When to harvest seeds
• How to save tomato seeds
• How to save sunflower seeds