Seed Collecting

Part of the joy of gardening is that there is so much you can do to help keep your garden blooming year after year – for free!  Collecting and storing seeds, keeping tubers, and propagating plants using cuttings from mature plants are all mainstays of the good gardener’s practises. It’s remarkable that you can produce dozens of new plants from a single flower, and the result of this is truly satisfying.

This is my first blog post charting my gardening endeavours for the Trust. Let’s hope we see these plants grow and feed bees next year. There is a discussion about this topic going on in the forum right now, click here to go view that topic. To find out which flowers are best for bumblebees, visit our Bee kind app.

Plants produce their seeds at different times of year, and the only way to know if the seeds are ready to be collected is to have a look for yourself. Without trying to generalise too much, you can tell when seeds are ready to be harvested when a hard outer case forms around them. This case is what protects them in the soil through the winter, and in most species is dull yellow or brown. If you harvest too early though, the seed won’t be fully mature and may not survive. On the other hand, leave it too late and all of the seeds will have fallen. Timing is everything.

As different plants have different ways of producing and releasing seeds, here are a few general tips for collecting seeds:

For those in pods (e.g. sweet pea and lupin), you should pick the whole pod when it turns from green to brown or black. Store the pod in a paper bag or envelope at room temperature, and as the pod dries, it will split and release the seeds. Leave the seeds to dry further for a few days, then remove the pods and any seeds that have split, and store or plant the seeds (see below for a guide to storing and sowing).


Lupin seed pods
 For flowers that produce heads of seeds (e.g. sunflower, cornflower, knapweed), simply wait until the flower head has become dry and husky– this usually indicates that flowering is well over, and that the seeds have formed. Test one or two flowers by splitting them in half, to see how developed the seeds are. If they are still soft and green, the seeds aren’t ready, and you’ll have to wait a little longer. If they are hard and dull yellow or brown, they’re ready to be taken. To harvest these seeds, squeeze them from the husk of the flower, making sure that remove any plant material that isn’t the seed. Leaving extra material can harbour disease or cause the seeds to rot, so it’s important to make sure this is all removed.    


Knapweed seed head with seeds

Poppies and other plants that produce tiny seeds that are stored inside hollow ‘heads’ are easy to take seeds from. You’ll know when they are ready when you see that the flower head is hard and not green. Shake the flower head – if you hear seeds shaking around inside, then you can simply pour these out – seed harvesting doesn’t get much easier than that!


Poppy plant with ripe seed heads (left) and poppy seeds (right)
 Some plants produce seeds that should be sown right after collection, because they don’t survive storage for long, or need to be exposed to the cold of winter frosts to initiate germination. Some of those include: cotoneaster, aquilegia, hellebore and honeysuckle. The majority of garden plants produce seeds that can be stored until spring. Some of the most common of those (which are bee friendly) are cornflower, nasturtium, poppies, sweetpeas, lupins, foxglove and sunflower. However, some of these are hardy enough to survive winter in the soil, and cornflower and nasturtium have both survived winter in the soil in my garden.

Any seeds that you are storing should be stored in an envelope (with the plant name written on), and placed in a glass jar with a sachet of silica gel. The silica helps reduce the moisture content in the jar, helping to prevent rotting. This should be kept in in a cool place throughout the winter.

Now that I have collected and stored my first batch of seeds this year, follow my blogs to see how to propagate plants using cuttings and tubers. I'll be providing updates on how the collected seeds and other plants fare, so check back!

For more information about collecting seeds and to watch a video on it, follow this link to the BBC Gardening website.


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