Collecting and storing seeds is suitable for many different plant species including shrubs, trees, perennials, annuals, aquatic plants, alpines, plants with bulbs, biennials, ornamental grasses, herbs and vegetables.
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When is the best time to collect seeds?
This will vary, depending on the species, but usually, the best time is late summer to late autumn.
Harvesting your own seeds can be enjoyable, but it also takes a little planning and understanding of what's required. Seed heads can ripen quickly, so you need to keep an eye on them and collect the seeds before they are dispersed by the wind.
The best time to collect the seeds, on average, is two months after flowering. It's preferable to collect certain seeds when they have developed, but are still green and relatively immature. This is the case with plants such as calendula, anemone nemorosa and ranunculus.
Collect seeds only from vigorous and healthy plants for the best chances of success. The healthier the plant, the better quality the seedlings and new plants will be. You will get true plants from the seeds and there will not be any hybrids.
Premature harvesting will result in seeds that will not germinate. Learning when they are ready to be collected comes with trial and error if you're new to gardening.
What are the most common types of seed?
There are many different varieties in the average garden. The most common types include capsules such as poppies; berries like holly; catkins including birch; pinecones; nuts such as hazel; euphorbia lathyris, otherwise known as "exploding" seed heads; pods including sweet peas; and winged seeds such as sycamore and acer. You certainly have a wide choice and the more time you can spend in the garden the better, as you can collect a wide diversity of different plants.
Aim to collect on a dry day, at the earliest opportunity after the seed heads have opened or ripened. You may be able to spot the ripening through the changing colours, as they will sometimes go from green to brown, red or black. You must collect them before they shed their contents, or it will be too late.
How do you collect the seeds?
Pick the seed heads, either on stalks or as single seeds. Lay them to dry on the greenhouse bench, in the airing cupboard, or on a warm windowsill indoors. You will need to keep the different types separate in clear containers so you can see what stage they are at.
It will help to label each container to remind you which species each set of seeds belongs to, unless you like surprises the following year! Putting them in a warm, dry place makes it easier to extract the seeds from the pods, capsules or cones.
To collect seeds from berries and fleshy fruits, mash them up in a sieve and rinse off the pulp in cold water. Leave the seeds to dry for a few days on paper towels on a tray or in a box where they won't be disturbed.
Check exploding seed heads every few days. Remove them from the stems when they turn brown and put them in a labelled container.
Collect nuts when they naturally fall off the trees, or place a sheet under the tree and shake the branches ‘til the loose nuts fall. Extract the seeds and clean off any surrounding chaff, as this material can rot the seeds, harbour mould and attract pests and diseases.
How do you store seeds?
You will need to sow some seeds immediately, such as hellebore, as their health can deteriorate if they are stored for a long time. However, most species can be safely stored until a suitable time of year for sowing.
Store the harvested seed in labelled envelopes or paper packets in an airtight container, with some silica gel or other desiccant to remove excess moisture. If the majority of seeds are left damp, they can rot before you have a chance to sow them.
However, some seeds that you must not allow to dry out completely include oaks, walnuts and magnolias. Store them safely in a box in a mixture of moist sand and coir compost for several months - they need moisture for germination. They will remain in good condition for many years if you store them in a refrigerator at 5°C (41°F).
Seed production can exhaust a plant, so some years will produce a good harvest, while others won't. The number of seeds produced can also depend on the weather. For example. a late frost, or a summer drought, can lead to reduced numbers.
When it comes to sowing the seeds, the best time for hardy plants including perennials, annuals and biennials is spring and early autumn. For less hardy plants, sow then in late spring when you can be sure any late frosts have finished.
Your hard work will be rewarded when your garden is ablaze with colourful blooms.