Seed sowing tips

Subtitle: All the things I wish I’d known when I started out growing flowers from seed

KEEP YOUR COOL

In my studio, there is a fridge as full as an apothecary’s chest, of labelled jars, boxes and bottles of magical specks of potential flowers. I am lucky enough to have a lot of yellow Japanese storage boxes from Niwaki and those, along with a Dymo labeller, keep me very much on track.

Yes, of course the fridge is also useful as an overflow drink chiller when we have parties, but for the vast majority of the time, it is full of seeds. Promise.

Now you don’t need to go out and buy a whole new fridge as a dedicated seed storage place, but the principles of cold and dark are solid ones. Some of the most habitual places that we keep seeds (the kitchen windowsill next to a radiator when they have arrived in the post, or in the greenhouse when we have been getting all our bits together to sow) will damage seeds and send their germination rates plummeting.

 I can tell you now, there is nothing more disappointing than feeling all the magic and the excitement of sowing seeds and having a blank seed tray and not knowing why. Seed that is too old or that has got hot is one of the main reasons. Oh, and this is one of the reasons why I don’t buy seed from garden centres, however tempting it is. Do you know how hot those places get in the summer? I do.  I worked in one for many years and it gets sweltering in August.

 Store in a cool, dark place. If you are really serious, put your seeds in a glass jar and add some of those silica gel sachets that come in handbag packaging. That’s where I keep my Piggy Sue.

DON’T SOW TOO EARLY

Do as I say, not as I do.

I am addicted to seeds. I love everything about them. I had to set up my seed business just to fund my habit and yes, I do very much dabble in my own supply. As soon as the yeast of spring starts to fizz in my veins, I get out the seed tin and plunge in.

This is a mistake. The air warms up before the soil does and just because I am dog  walking with one less jumper than I was last week doesn’t mean that the soil is warm enough to bump start seeds into life. And even if I use the warmth of the kitchen to get them germinating, it is going to be a long wait before the conditions in the field will be clement enough to plant out.

Steady that hand. Restrain yourself. There is much to be gained from waiting.

Even with seeds you may be starting indoors, it is worth taking your cue from Mother Nature. When your outdoor spaces start to cover with the green fuzz of germinating weed seeds, the magic moment has arrived. Go hell for leather on the seed sowing now, not before.  Exceptions to this are flowers that struggle to fit all their growing and flowering in one season and that need a bit of a head start.  For example, I always sow Cobaea scandens in February and even then I am impatient to see it by the end of August. Aquilegia also love an early start.

Or seeds that don’t mind a bit of cold growing time after they are up and growing (that’s basically just sweet peas).

CONSISTENCY OF TEMPERATURE MATTERS

My toppest tip that I have learned in the last year or two has been from the wonderful Charles Dowding.  It is worth hanging on his every word when it comes to matters growing but I have been particularly intrigued by his thoughts, not on the temperature of germination per se, but on the consistency of warmth.

What he says is that seeds will not germinate if the nights are cold, even if the days are warm and spring-like. Plants don’t mind warm days and cold nights (it is worth really grasping that what seeds need to germinate and what seedlings need to thrive are very different) but seeds do. Fluctuations and drops in temperature across the day and night mean they sense that their time has not yet arrived, and they will wait for more comfortable conditions.

So use this knowledge to your advantage. Where the one place that stays relatively warm overnight? Houses.

Human beings don’t like wildly fluctuating temperatures or brutally cold nights any more than seeds do, so let’s make the most of the coincidence. Invite those seeds into your home. I am lucky enough to have a whole room for seed sowing now. The new cottage is full of damp and I had to invest in a massively beefy cast iron radiator to try and dry the walls out. The result? A big, dark room with a constant temperature of about 15 degrees. You bet I’m making the most of it.

Germination in the house, growing on outside in the elements.

It doesn’t have to be glamorous, just cosy.

CHILLING MAKES A REAL DIFFERENCE

It has taken an embarrassingly long time for me to catch on to the importance of pre- chilling seeds. Some plants won’t germinate—or will germinate poorly or irregularly — unless their spring follows a prolonged period of cold weather. You can either do this by sowing them in autumn and hoping for a few good hard frosts, or you can fake it. This process is called stratification. It needs moisture and cold, not just cold, so the fact that I keep my seeds dry in a fridge isn’t enough. The way to do it is simple though; a little ziplock bag, a tablespoon or so of moist, neither wet nor dry, compost, shake in the seeds and put it in the fridge. If you have any Covid test packs knocking around still, raid them. They are a rich source of little ziplock bags. I swear by the freezer for Bells of Ireland and delphinium. They do really need a bit of mean treatment. About a week should do it.

I leave a month for fridge chilling to be sure, so it is worth getting organised in February for March sowing.

Aquilegia

Astrantia

Baptisia*

Bells of Ireland

Campanula

Clematis

Delphinium & larkspur

Echinacea

Eryngium

Poppies

Phlox

Rudbeckia

Sanguisorba

Scabiosa

Thalictrum (meadow-rue)

Viola

Remember to label very carefully indeed, especially if other people also use your fridge. And put a note in your diary when it is time to get them out. I have been known to find a parcel of Bells of Ireland at the bottom of a frosty freezer after a year. And yes, they still grew.

 *if you can germinate Baptisia, then absolute kudos to you. I have never managed it.

WATER FROM BELOW

So you’ve waited. You’ve got your seed tin out from the cool and the dark of underneath the bed in the spare room. You have sourced the best, peat-free compost and lovingly sprinkled on your seeds. They need moisture to germinate and so you find a watering can.

Stop.

Even with the finest rose, tiny seeds are going to go all over the place if you water from above. The only way I water, and the way to make sure that your seeds have a bed that is wet but not sodden, is to water from below. Where I have seeds, I have a tray of water. Just dip in the whole tray, wait for the surface to darken and lift out again. Let it drip a bit so the excess water comes out and then on to the next one.

For the sake of your paintwork, if you are putting pots and trays on windowsills, make sure you have a plastic or metal tray underneath. A compost bag as a liner won’t cut it; somehow the damp always finds a way underneath and will ruin paint faster than anything else. Exception to this? Sweet peas again. I grow mine in cardboard inners and if you soak them from below, they go mouldy and collapse. Just a dribble from the top.

& a bonus tip for you: Think cake

One of the easiest mistakes to make is to tamp down your compost too hard. Everyone seems to have one of those wooden tamper things and they can be fab, but keep a light hand. Seeds need warmth, moisture and oxygen to germinate but the oxygen isn’t coming directly from the air that we breathe, it is in the little pockets of air between the particles of compost. Press down too hard and you’ll squash all the air out. A little shake to settle the compost, and little tap on the bench to get any bigger gaps closed, and you’re done.  The texture of a really good Victoria sponge. If it’s more Dundee cake, you’ve gone too far.

This is also why it is entirely possible to drown a seed. If the compost is waterlogged, those crucial air pockets fill with water and the roots can’t reach the air.