As autumn gets into its stride, many perennial plants are going over and if flower heads are left on the plant, they will go to seed.  Last year I benefited greatly from the seed distribution scheme run by the Hardy Plant Society.  This scheme relies on donations from members all over the world – last year there were over 2000 varieties to choose from.  This year I’m going to save some seed for myself, but send the majority of what I collect to the HPS.  I confess that at the back of my mind I’m aware that this will entitle me to an extra 10 seed packets in my order.  It’s all about me!

Some plants have seed dispersal mechanisms that make it difficult to collect seeds, but for many the procedure is broadly similar and straightforward.  If there’s a particular flower I want to grow from, I make it obvious which stem I want to collect the seeds from.  On a given plant or group of plants, there might be a particularly interesting flower that would be good to propagate. For instance, I have my eye on some particular rudbeckia that had fantastic markings, and some helenium that were unusually coloured in comparison to their stable-mates.  This is a good idea as once the flowers have faded and the petals dropped, the seed heads all look the same.  Trust me when I say you won’t be able to tell for sure which one is which. I have used various methods in the past – tied some twine round the stem, or a coloured ribbon, and this year I have just stuck a plant label next to the base of the stem.  This is mainly because I had some in my pocket at the time, no cunning plan as such.

The seed heads need to be ready to give up their seed. If the pod is still soft and green it’s too soon, they should be brown and dead-looking. Next thing is to make sure the seed heads are nice and dry. Ideally, wait for a dry, breezy day.  If they’re nice and dry I go straight to the next step, but if the weather is not cooperative, I cut the stems off and leave to dry on some newspaper in the shed.  With some plants the dry seed will come pouring out of the seed heads, some pods are more reluctant to release their passengers.  Rather than wrestle with individual seed pods, I snip off all the pods and put them all in a plastic tub, which importantly has a tightly fitting lid, then give it a good shake, up and down, side to side, for a minute or so.  This loosens the seeds nicely.

How do I collect seeds from plants?

It’s possible to separate the seeds from the other detritus manually, but that is extremely fiddly.  For teeny seeds, I use a fine metal sieve that I temporarily liberate from the kitchen, over a soup bowl. I pour the contents from the tub into the sieve and gently shake that about.

Why collect seeds?

The seeds usually fall through pretty readily into the bowl.  Some debris usually comes with the seed, but that is easily removed just by blowing very gently across the bowl – the fluff is much lighter than even the teeny seeds. Gently though – the seeds are light themselves and you don’t want seeds all over the place.  If the pods were dry in the first place, or have been dried out first, the seeds will also be very dry.  They must be nice and dry before storing or they might rot.  I just use whatever envelopes are handy, pouring the seeds in carefully.

How to save seeds

By the way, both sieve and bowl will need a good wash in hot water afterwards, a dishwasher hot cycle is good, as some seeds are toxic.

If you plan to keep seeds for years, and many do store for a long time, it’s important to consider storage methods.  A sealable tub or box is good, particularly if some silica gel is included to capture any remaining moisture. The storage box should be kept somewhere dry and cool, not too hot, humid or damp.  If you have room, seeds can be kept in good condition in a freezer for years.

Clearly label the envelope or packet, whatever, with the plant name, variety, date collected, and any other information that might be useful months or even years in the future.

Because propagation by seed relies on a planty sexual encounter, in most cases there is another flower involved somewhere.  50% of the genetic material in the seed comes from the parent plant, but the other 50% comes from another flower. It might be from the same plant, from a neighbouring plant in the same group, from a different group of the same plants elsewhere in your garden, or just as likely, from someone else’s garden.  Those bees get about.  One of the joys of propagating from seed collected this way is that you never really know what you’re going to get when you sow them. The resulting plant could be similar looking, or have quite different flowers, occasionally a really fantastic one. At its most basic, this is how plant breeders get new varieties, although I expect it’s done a little more scientifically.

Even if you don’t plan to grow from seed yourself next year (what!?), I would encourage you to find a local seed exchange and donate some seeds, they’ll be grateful.

Some plants in my garden that set seed that is easily collected this way are:

  • Rudbeckia
  • Helenium
  • Gaillardia
  • Lychnis coronaria
  • Digitalis
  • Echinacea
  • Aquilegia
  • Geum
  • Carnation

Why not give it a try?

I’ll be back soon with more propagation nonsense.