When it comes to gardening in a self-sufficient way, nothing beats saving your own seed.
For our seed bank at the Botanic Garden, we collect, dry, clean and store seeds of wild Welsh plants for future conservation and restoration uses.
Many of the techniques we use to professionally conserve this seed can be applied to saving seeds from your garden – here’s a guide.
Timing is key
It pays to collect seed when the weather is dry. This reduces the amount of additional drying needed and minimises the risk of fungal disease or rotting.
To make sure the seed is fully ripe, collect when the plant is ready to naturally disperse its seed. Unripe seed is very unlikely to germinate.
Getting this timing right means keeping an eye on the development of seed heads and fruits you want to save seed from, to catch the seed just before it drops or is eaten by animals.
For dry seed heads like capsules or pods, look out for a change in colour from green to brown and signs of splitting or natural seed shedding. You can sometimes hear seeds rattling inside ripe capsules or pods if you give them a gentle tap or shake.
For fleshy fruits like berries, look for softening and a colour change from green to red or black.
Checking seed quality
To make sure seeds are healthy and pest-free, it is worth looking closely at them before collection. We always do a ‘cut test’ before collecting seed for the seed bank, by taking a few seeds and cutting them in half to check inside.
Healthy, viable seed is plump and full of contents called the endosperm, usually white in colour.
If you find flat and empty seeds without endosperm, these will not be viable – many factors can cause this, such as a lack of pollination. It can be helpful to attach small seeds to sticky tape, before cutting them in half with nail scissors. A hand lens or magnifying glass is useful to see small seeds up close.
You may find evidence of insects inside the seeds, such as the larvae of seed weevils, common for plants in the pea family. Avoid collecting any insect damaged seed.
Collect from healthy looking plants, as seed is more likely to have a high viability and be pest- and disease-free.
Harvest your seed
Collect seeds by hand or by cutting whole ripe seed heads. If collecting by hand, seeds that pull away easily from the plant are the ones to collect as they should be fully mature.
Place the material into breathable bags. Cotton bags such as tote bags or old pillowcases are perfect.
Paper bags are also good. Remember to label your collections.
Dry your seed
The viability of seed can be greatly knocked if the harvested plant material is left damp.
Air-dry the material by spreading it out on newspaper somewhere warm but not too hot, and out of direct sunlight – a shed or inside a house is ideal.
This drying stage also gives capsules a chance to fully open and release the rest of their seed.
Handling fleshy fruits like berries is a little different. Spread the fruits out in ambient conditions until the flesh is soft enough to turn into a pulp, ready to extract the seeds.
Clean your seed
The next stage is to sort the seed from the other waste plant material, known as chaff.
It is not essential to extract all chaff, but it is best to extract the bulk of it, as it can contain insects and contribute to fungal outbreaks when the seed is sown.
For dry seed heads, the cleaning involves carefully extracting seeds from their casings, e.g. shaking seeds out of their capsules, gently breaking capsules (a rubber bung is good for this) or shelling pods. A kitchen or soil sieve is really useful to extract the seeds from the chaff. It is advisable to wear gloves and a dust mask and do this outdoors, as it can be a very dusty process that can trigger allergies.
To extract seed from fleshy fruit, gently mash and rinse away the soft fleshy pulp with water, catching the seeds in a sieve. Spread the seeds out on newspaper to air-dry for about a week, replacing the newspaper if it stays damp.
Store your seed
Once your seed is fully dry, place it in small paper packets or envelopes (avoid plastic as excess moisture may be trapped inside). Your seeds are then ready for safe storage – read how to do this here.
Be aware that seed collected from garden varieties may not ‘come true to type’, meaning that offspring may be different from the parent – for example, seed grown from yellow nasturtiums may turn out to be orange nasturtiums.
If you want to save your own seed from vegetables, grow ‘open-pollinated’ varieties (not F1 hybrids). Such varieties are pollinated naturally by insects or other means and will come true to type.
This blog was written by Dr Kevin McGinn, Science Officer for the Growing the Future project.
This project has received funding through the Welsh Government Rural Communities – Rural Development Programme 2014-2020, which is funded by the European Agricultural Fund for Rural Development and the Welsh Government.