You might have landed on this blogpost quite by chance, having found it via a search engine, in which case, hello. If you landed via a link from our Seed Saving Kit, I do hope you're enjoying it, and hopefully you'll find some additional tips in here about growing plants from seed.
I absolutely love collecting seeds from the plants in the garden - to the point that it's a bit of a compulsion. From June onwards I try and keep a few paper bags in my pocket when I'm working in case I spot something ready to collect. Of course this means that every job takes twice as long, as I keep getting distracted…
I'm fascinated by all the different shapes of seed heads and seeds, and the wonderfully inventive ways that plants have of launching their offspring out into the world. Some are tiny and light, like Digitalis (Foxglove) seeds, almost dust. I guess these can travel quite a way on a breeze. Hardy geranium seed pods have explosive catapults that fire in five different directions. Others, like Orlaya grandiflora (White laceflower), have hard little hooks on the seeds, just like velcro, to catch on a passing animal and be scratched off elsewhere. One of my favourite seeds is pictured above. It's from a low growing grass, Stipa tirsa, which has long feathery ‘awns’, perfect for flying away on the wind. These seeds have a second trick up their sleeves too. If you look closely at the photograph, you can see that the stiff section above the seed is twisted. When the seeds touch the ground, the awns twirl round, drilling the seed into the ground until it's at the right depth. Isn't that just wonderful?
Every year I collect seeds from around 100 different plants from the garden. Where we have enough, we put some on the website for sale, while others are only collected in small quantities and we keep them back to produce new plants for the nursery - it's how we manage to keep our range so varied.
You might think that after 18 years here, we would have the job of growing plants from seeds down to a fine art, but it's not that straightforward. I've shared below some of our tips for growing plants from seed. It's just a brief summary - I could write a whole book on the subject. Maybe I will :-).
Before we start, it's worth answering one key question. What, exactly, is a seed? (If you are a botanist or a biologist, you might want to look away now, for my answer isn't going to use the language that you'll find in horticulture text books). Inside most seeds is a tiny, pre-formed plant, complete with a little shoot and a root bud, attached to a food store and wrapped in a hard protective case. You could think of a seed as an embryo plant sealed in an incubator, with all its systems shut down, awaiting the right conditions to grow. If you carefully slice a broad bean in half, you should just be able to make out the tiny, white plant on one side. It's really quite fascinating to see.
It takes a plant a lot of energy for a plant to produce a seed. Ensuring that it grows, thrives and produces more seed is vital to continuing the existence of the species. So plants take great care to ensure that seeds will only germinate when there is a good chance of success, using an armoury of defensive strategies. Some tiny seeds will only germinate when the can detect light, which tells them they are close enough to the surface to reach it. Lots of seeds will only germinate after experiencing a lengthy cold spell. This tells them that winter has happened and it is probably spring. Others have a tasty coating on the outside which is removed when digested by an animal, then passed through. This, of course, ensures they are deposited in a rich, fertile heap of manure.
What is extraordinary about this, is that it tells us that seeds have sensors. Some very tiny seeds, smaller than a pinhead, like Poppy seeds, can detect light, even when the seed is decades old. That's why the Flanders fields turned red with poppies - they were thrown to the surface by the shelling, detected light and grew. Others have temperature sensors and can record time - they know how cold it has been and for how long. Isn't that just extraordinary?
Interesting yes, but so what, you might be thinking? It matters because when we sow seeds, we're asking them to respond and grow, and if we haven't given the seed's incubator the right conditions, it simply won't.
So what have we learned in our years of growing plants from seed?
1. Firstly, think about where a plant comes from. Plants that come from parts of the world that never experience frost have no need to worry about accidentally germinating in winter, so they will usually germinate any time you offer it moisture and warmth. Tomatoes for instance, originally from South America, will germinate indoors any time of year. Seeds of plants from climates with cold winters are much more likely to have a built in mechanism for ensuring spring really has arrived before growing.
Seeds that need a winter chill can be mixed with some damp vermiculite and placed in a fridge in a plastic bag, or sown in a seed tray in autumn, topped with fine grit and left outside, like this tray of Anemone seeds that I sowed earlier this week.
2. Seed size is a useful clue too - usually, the smaller the seed, the closer it needs to the surface before it will germinate. Cover seeds in no more than twice their own depth, or with something that lets light in, such as vermiculite. I use a board to gently flatten the surface of a seed tray before sowing seeds. This ensures that it is evenly firm (I don't press hard) and there aren't any deep holes for small seeds to fall into.
3. Ifseeds have a fleshy covering, wash and dry them before sowing - the coating might have a chemical inhibitor in it.
4. The compost that you sow seeds into needs to have little air pockets all through it. This is wrong place to get into an explanation about respiration. Just trust me that root growth needs air. Wet, claggy compost is no good at all - your seeds will probably just rot. But don't let the seeds dry out either. Yes, it can be a difficult balance to strike. I sowed some seeds yesterday that are going to stay outside all winter, covered in grit. This is the mix I used for the Anemones above - it's a blend of peat-free compost, fine bark, perlite and sand. Feels about right to me.
5. Seeds have their own food store and some dislike emerging into rich compost that can ‘burn’ the new roots. So we start seeds off in a low nutrient mix and then either pot them up when they're big enough to handle, or give them a liquid feed.
6. If you sow seeds too close together, their roots will touch and compete for space when they are far too young and none of them will grow really well, or some will outcompete the rest. These Anemone seeds are too close together, I think - they're almost touching now and haven't started growing yet.
And these are about the right distance apart, I feel.
The only way to become successful at growing plants from seed is to try it. It's helpful to make notes of what you sowed, when and how, what worked, and what didn't. If you're new to growing from seed, try easier, cheaper seeds first - or even better, ones you've collected from your own garden :-).