Collecting and Preparing Seed

From summer onwards, you can start gathering seed produced by the plants in your garden. Seed is usually produced in abundance, so there is never any shortage in the supply. The trick is to collect it when its ripe before the plant discards it.

Cut the stems just as they are starting
to split and shake the seed out.

When can I collect seed?

Seed should be harvested when it is ripe, usually in late summer to autumn. Unripe seed will not germinate. If you want seed from a particular specimen, watch it closely so that you do not miss an opportunity.

Is seed-collecting suited to propagating particular species of plant?

Propagating by seed is an excellent method of producing sturdy, virus-free plants. You can only reproduce certain species by this method and the results are not reliable, depending on the genetic stability of the parent. For example, with the Lenten hellebore (Helleborus orientalis), which is worth trying, the flower colour cannot be predicted. Wisteria seedlings, on the other hand, often do not flower well.

Vegetative methods produce plants that are identical to the parent, but only limited material may be available, whereas seeds are usually available in abundance. Some plants have seeds contained in papery cases which split open when the seeds are ripe.

Which common garden plants are easy to grow from seed?

  • Acanthus
  • Agapanthus
  • Berberis
  • Clematis orientalis
  • Clematis tangutica
  • Cotoneaster
  • Helleborus orientalis
  • Juglans regia
  • Lathyrus latifolius
  • Lilium regale
  • Lunaria annua
  • Malus
  • Nigella damascena
  • Pyrus salicifolia
  • Quercus
  • Sorbus
The Lenten hellebore (Helleborus
orientalis) often seeds itself in gardens.

Can I grow hybrids from seed?

Hybrids are created by crossing two different species. Complex hybrids may combine the genes from several species introduced by later crossings. Hybrids are usually very robust plants with large flowers. Some do not even produce seed, but if you collect the seed from those that do, the resultant seedlings will not resemble the parent. They will revert to one of the hybrid’s ancestors, which may not be a plant that has any garden merit. 

How do I extract the seed from fleshy berries?

Cut the berries of plants such as Sorbus and Cotoneaster in autumn when they are soft and ripe – ideally after the first frosts. Squash the 
berries to release the seed, then wash in a small bowl of lukewarm water. 
Dry the seed on kitchen paper before you sow it.

How do I extract the seed from hard fruits?

To extract the seeds from hard fruits such as Malus, cut the fruit in half with a sharp knife to expose them. Apple seeds are dark brown when ripe. Remove them with the tip of 
the knife, discarding any that were accidentally damaged when making the cut.

How do I extract seed from the cone of a conifer?

You will often see cones on the grass around a conifer in autumn. To extract the seed, place a sheet of paper under the cone, then tap it sharply on the table. The seed should fall from 
the cone. If the cone is fully open, the seeds may already have been shed.

What should I do if the conifer cone is tightly closed?

You can encourage cones to open in one of two ways. Either place the cone on a sheet of paper near a gentle heat source, such as a radiator, or put it in a bowl of lukewarm water. Within 24 hours, the cone should open, and you will be able to extract the seeds.

Can I store seed?

Seed can be stored in a cool, dry place in paper envelopes or screwtop jars. Label with the plant name and the date of collection. Often packets of seeds will germinate long after the suggested date on the packet, and it is always worth trying.

What is stratification?

The seeds of many hardy trees and shrubs have hard coats that have to be broken down before the embryo within can begin to grow into a plant. This normally occurs naturally over winter. Freezing weather softens the hard coat, so that the new plant can emerge. Take any batch of seed, however, and the temperature at which this happens will vary – some will germinate at lower temperatures than others. So, if you sow the seed outdoors, some will germinate in year one, while others will only germinate after two or three years.

Can I stratify seed artificially?

Although you can sow seed and place the containers outdoors, waiting for nature to take its course, you are gambling on suitable conditions occurring over winter that will break the seed’s dormancy. To speed up the process, you can stratify the seed artificially before sowing. Mix the seed with damp perlite or vermiculite and seal in a clear plastic bag. Label the bag with the name of the plant and the date, then place in a refrigerator for three to six weeks. Then sow 
the seed as normal and place the containers outdoors. (Some seed may actually germinate in the refrigerator.)

Which tree and shrub seeds need stratification?

All true species that produce seed such as:

  • Acer
  • Amelanchier
  • Betula
  • Carya
  • Cotoneaster
  • Euonymus
  • Fagus
  • Hippophäe
  • Sorbus
  • Viburnum
Extracting seed from fleshy berries

1: Squash the berries, which should already be soft, between finger and thumb to release the seed. Discard the flesh.

Picture of Patio Planting

2: Wash the seed in a shallow bowl filled with lukewarm water to remove all traces of the flesh. Dry the seeds on kitchen paper.

Sorbus produces its seed in fleshy
berries – red, yellow, pink or white.

What is warm stratification?

The plant family Leguminosae contains many familiar garden plants including sweet peas (Lathyrus odoratus), laburnums and lupins. 
To accelerate germination of the seeds from this family, some gardeners like to soak the seeds in warm water for up to 24 hours prior to sowing.

How do I deal with large seeds?

Some seeds, such as oak (Quercus) 
and horse chestnuts (Aesculus), have a tough outer coating that inhibits germination. It is this coating that allows seeds to remain viable in the earth for several years without germinating. This can be overcome using a process known as scarification.

What is scarification?

Scarification involves a physical breaching of the seed coat, either by cutting or abrasion. If you are dealing with a large seed, such as an acorn or chestnut, nick the tough outer coat with a sharp knife, taking care not to damage the tissue beneath. The abrasion allows in air and moisture, allowing the seed to germinate. 
You can breach the seed coats of smaller seeds such as sweet peas by rubbing gently with sandpaper or 
by shaking them in a small jar containing sharp sand.

Are there any other pre-treatments for seeds?

The seed coatings of some shrubs 
can be softened by soaking the seed for a few hours in water – hot or 
cold, depending on the species. 
The following all benefit:

  • Arbutus (cold)
  • Camellia (cold)
  • Caragana (hot)
  • Coronilla (hot)

How do I deal with the seedlings?

After they have germinated, keep 
the seedlings growing strongly by watering and feeding them regularly. Keep them in a cold frame over the first winter. Pot them up in spring, either individually or in groups of three or five. They should be large enough to plant out in the garden after two to three years.

Sowing seed

1: Fill a pot with multi-purpose or seed compost (soil mix). Have spare plant pots to hand and some gravel and a plant label.

Picture of Patio Planting

2: Fill each pot with compost, then water it well and allow the container to drain – the compost surface should be just moist.

Garden Planning

3: Seed should be covered to its own depth. Very fine seed can be surface sown, then topped with a fine layer of sieved (strained) potting mix, horticultural grit or sand. For larger seeds, make suitably sized holes in the compost with a dibber, then draw the surrounding compost over.

Garden Planning

4: Cover the compost surface with a layer of horticultural grit or sand. Place the containers outdoors in a sheltered place. After germination, protect the seedlings from slugs and snails. Place them in a cold frame on nights when hard frost is forecast; remove them again the following day.