Hands holding dry brown seedheads and pods over paper envelopes on a wooden potting bench — AI-generated image, not a photograph of a real person or place.

SEED SAVING, IN PLAIN ENGLISH

This year's flowers,
next year's seeds.

A ripe seedhead is a free packet of seeds, if you catch it in time.

The RHS says seed is set about two months after flowering. Collect it dry, keep it cool, and choose the right plants: only some come true from seed, and F1 hybrids do not.

≈ 2 months from flower to seed

Check a crop

Pick healthy plants
Dry before storing
Cool and dry lasts
Small packets, long lives

THE SHORT ANSWER

Collect ripe,
store cool and dry.

Seed saving is mostly timing and storage.
The rest is knowing which plants will come true.

WHEN TO COLLECT

Watch the seedheads

Ripe seedheads often turn from green to brown, black or red. Pick them on a dry day before they open and shed their seed.

Four steps

TRUE TO TYPE

Not every plant comes true

Save from open-pollinated varieties, not F1 hybrids. Crops such as brassicas and runner beans cross easily, so keep varieties apart.

Check a crop

STORAGE

Cool and dry

Garden Organic's rule of thumb: storage life doubles for every 5°C drop in temperature and 1% drop in moisture content.

See the numbers

A glass storage jar of dried bean seeds on a cool pantry shelf — AI-generated image, not a photograph of a real person or place.

FOUR STEPS TO SAVING SEED

Collect, dry,
pack and label.

The RHS rates seed collecting as easy to moderate. Most of the work is in timing and keeping things dry.

Choose healthy plants
Collect from healthy, vigorous plants on a dry day. If the plants are in a street or park, ask the gardener or owner first.
Catch the seed
Pick seedheads as they change colour, before they open. For exploding seedheads, place a bag over them and shake.
Dry and clean
Lay seedheads out to dry, then remove the chaff, which can harbour moulds, pests and diseases. Mash berries in a sieve and rinse away the pulp.
Pack and label
Keep dry seed in labelled paper packets in an airtight container in a cool place. A fridge at 5°C keeps most seed viable for many years.

TWO NUMBERS WORTH KNOWING

Drier lasts longer,
and old seed is kept.

One rule of thumb for storing seed,
one figure from a library that keeps seed alive.

2× longer

Seed storage life, for every 5°C cooler and 1% drier

Moisture is probably the most important factor: a dry seed lasts much longer at room temperature than a moist seed in the fridge. Fresh seed can be 10 to 15% water; drying to around 5% prolongs its life.

STORAGE · GARDEN ORGANIC

800+

Varieties held, many no longer sold

The library holds rare landrace and heirloom varieties and others no longer available to buy. Home growers can help by becoming seed guardians and growing seed for it.

HERITAGE SEED LIBRARY · GARDEN ORGANIC

Garden Organic warns that heat destroys seeds: they should never be exposed to temperatures above 35°C. Some seed, such as parsnip, should always be used fresh.

A QUICK CROP CHECK

How easy is it
to keep seed true?

Pick a crop. The bar shows how much care it takes to save seed that grows like its parent.

Crop check

Choose a cropPeas and French beansTomatoesRunner beansCabbages, beetroot and onionsAny F1 hybrid

Peas and French beansRarely cross

These inbreeding vegetables will not cross with each other, or cross rarely. Some precautions are still worth taking.

TomatoesSlight variation

Variation between plants is slight. Soak the wet seed for a few days to remove the pulp, then dry it.

Runner beansCover the flowers

Runner beans are outbreeding. Garden Organic suggests covering the flower trusses you want seed from, to keep out insects carrying other pollen.

Cabbages, beetroot and onionsIsolate varieties

Brassicas, beetroots and alliums cross readily. Grow one variety, keep varieties far apart, or flower them at different times.

Any F1 hybridWill not come true

The RHS says seedlings from a hybrid will be extremely variable. Save from open-pollinated varieties instead.

Sources: Garden Organic, Preserving varietal purity and Seed storage for longer life; RHS, Seed: collecting and storing.

Based on Garden Organic's Heritage Seed Library guidance and the RHS.

A runner bean plant in a vegetable garden with a fine net bag tied over one flower truss — AI-generated image, not a photograph of a real person or place.

WHEN NOT TO DRY

Some seeds
hate to wait.

The RHS says some seed, such as hellebore, is best sown immediately, because it loses viability in storage. Most seed germinates best if sown as soon as it ripens.

Others must not dry out at all: walnuts, oaks and magnolias can be kept in a plastic bag of damp vermiculite or sand for several months. When taking stored seed out, Garden Organic suggests letting the jar reach room temperature before opening.

Questions

Questions people ask

When should I collect seeds?

As a rough guide, seed is set about two months after flowering. Collect on a dry day as the seedheads change colour, before they open and shed their seed.

Can I save seed from F1 hybrids?

You can, but it will not come true. The RHS says seedlings from a hybrid will be extremely variable, so save from open-pollinated varieties.

How should I store saved seed?

Dry it, then keep it in labelled paper packets in an airtight container somewhere cool and dry. A fridge or freezer will keep it for longer.

How long does saved seed last?

Garden Organic says it is impossible to say exactly. Germination falls after the best storage time, but old seed is still worth trying before you throw it away.

Why did my plants not set seed?

Some plants are sterile, and in species like holly, male plants never bear seed. Seed production can also vary from year to year with the weather.

Sources

Updated 15 October 2026

This year's flowers,next year's seeds.

Collect ripe,store cool and dry.

Watch the seedheads

Not every plant comes true

Cool and dry

Collect, dry,pack and label.

Choose healthy plants

Catch the seed

Dry and clean

Pack and label

Drier lasts longer,and old seed is kept.

How easy is itto keep seed true?

Some seedshate to wait.