‘Collecting and saving seeds is a joy that can’t quite be matched by any other garden task.’ Photograph: Clare Gainey /Alamy

Autumn fills my pockets with strange seeds. Sometimes I wrap them up in slivers of paper, named and dated; sometimes I shove them deep in pockets from which I know they may not surface. Yet most find a suitable home, such as the white, everlasting pea with the prettiest pink edging, taken from my mother’s garden to grow in mine. These are best sown into pots and put in a propagator to germinate, and then booted outside somewhere frost-free for the winter: they can be slow to germinate, so be patient.

Collecting and saving seeds is a joy that can’t quite be matched by any other garden task. It’s partly the thrift and, like jam, you get to be generous: “Oh, please take some home with you.” Then there’s something wonderful about understanding the cycle: when to harvest, how to store, when to sow again.

Gather seed on a dry day. Damp seed can quickly become unviable, or rot (or, like one bag of echinacea I was waiting to process, germinate there and then). The best receptacle for collecting seeds is a clean, dry bowl or bucket, or, if the seedheads need further processing, paper bags. Bags with handles (the sort that posh delis hand out) are ideal, because you can hang them up somewhere cool, dry and out of direct sunlight.

The seedheads will often naturally shed their seeds for you, but some seeds need to be prised out. One of the easiest ways to do this at home is with a pestle and mortar. Give the seedheads a light bashing: don’t mash or grind – you’ll have nothing left. Then tip the whole thing into a sieve to remove the chaff.

If the seeds are small enough, they will fall through; if they are too large you can carefully grind the chaff through instead. You can buy sieves specifically for seed cleaning. Professionals use brass ones with an endless gradation down to the finest of seeds. These cost a bomb though (potters’ glazing sieves are a fraction of the cost). But for most of us, the flour sieve is adequate.

If you are left with too much chaff, you can learn to winnow. The easiest way is to use two large bowls or trugs, and do it on a slightly breezy day (if there’s no wind, steal a trick from Brown Envelope Seeds and use a fan). Hold one bowl up high and the other lower down, then pour the contents from one to another. The breeze (or fan) will blow away the chaff; the seeds, being heavier, will fall into the bowl.

Store seeds somewhere cool and dry, in paper envelopes, little plastic bags, fancy seed packets (there are numerous designs on the internet), or whatever other receptacle you see fit. To store seeds for the long term, place them in an airtight container in the freezer.

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