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Perfect for gardening enthusiasts at any level, this podcast is your companion to cultivating success and beauty in your own backyard or flower patch. Hosted by Jane Westoby from Fuchsia Blooms Florist and The Hampshire Seed Company.
Each episode is a treasure trove of practical tips, expert advice, and insider flower farming guides designed to help you sow and grow with confidence and harvest with pride. Whether you’re dreaming of rows of neat vegetables or cutting flowers for bouquets all year round, we’ll walk you through every step.
Let’s grow together!
5. Full Transcript Seed Stratification
Jane Westoby (00:05)
Welcome to the Blooming Garden podcast with me, Jane Westoby from the Hampshire Seed Company. Each week I'll be sharing my journey and the inspiring journeys of my guests as we delve into the world of sowing and growing. So whether you're just starting out and you need advice on the basics or you're further along your garden journey and looking for expert tips, we've got something to help you navigate through the seasons with success. Together,
We'll explore the joys and the challenges of gardening, celebrate the beauty of nature and discover how you too can make the most of your growing space, whether you're a gardener or a flower farmer. So grab your gloves and join me on this blooming adventure.
So today I will be diving into an essential, but sometimes often overlooked part of the seed sowing journey, which is seed stratification. And I just wanted to catch you early before the season really kicks off because if you've ever tried growing certain types of seeds over and
over again with no luck, then stratification might be the missing step in your process. So what is seed stratification? So at its core, it's really just about recreating the natural conditions that seeds need to wake up to start germination. So some seeds have this built in mechanism.
which protects them from sprouting at the wrong time. So if you think about it in nature, seeds might drop from the plant in autumn, but they don't want to germinate right before winter because they just won't be able to grow. instead, will lie dormant on the forest floor and they'll wait for the right combination of conditions to signal that it's time to grow. Okay.
So let's just start with the basics. all seeds need water and oxygen to germinate. These are essentially the two non-negotiables. Without those two, you simply won't get anything. But then there are two big variables which make the biggest difference. And this is where you can get quite a lot of problems. And here's the kicker. Not all seeds are the same.
The conditions that they need depend on the habitat that they are naturally adapted to. So for example, seeds from plants native to cold climates, they will often require a period of cold stratification, which just mimics the winter chill that they would experience in the wild. And on the flip side, there will be seeds from plants in warmer climates.
which might need heat or fluctuating temperatures to trigger their germination. So if you think about hardy annuals, we also call them cool flowers. So they like cool temperatures and they will often require cold stratification. So flowers such as or Orlaya and Dacus, Larkspur and even Bells of Ireland, these all need a period of cold.
and will also benefit from some fluctuating temperatures. So by sowing them in the autumn time and leaving them in a cold greenhouse or a polytunnel or a...
cold frame, mother nature will actually do this work for you. So with the temperatures dropping at night and sometimes freezing, that's ideal conditions for these flowers because they just won't germinate if it's too warm. So if you're sowing seeds in springtime, which you might also want to do to get a succession of blooms,
with these flowers. or Lyre if you sow it in the autumn, it will flower in the springtime. But if you sow it in springtime, you'll get it during the summer period. So it is good for succession. But you would need to give them the same conditions for germination. And the easiest way to do this is to simply just put the seeds in the fridge for a few weeks.
At its basic level, this will do the trick. But if you want to go one step further and get an even higher germination rate, then the trick is to take the seeds in and out of the fridge to mimic Mother Nature. So in the morning, when you make your tea or your coffee and you take the milk out the fridge, you pop your seeds next to the milk jug.
and you'll remember to take them out. So take those seeds out the fridge in the morning when you make your coffee, leave them on the countertop all day long. So they'll be warmer. And then in the evening, maybe when you're making dinner, just pop the seeds back in the fridge again. So if you do this for a few weeks, you will get the absolute maximum germination rate possible for those seeds. Obviously you have to give them the rest of the conditions that they require, but this is a really, really good start.
So some perennials and bulbs also need this same kind of stratification like bluebells, astrantia, aquilegia, lupins and angelica. These, I don't even put these in the greenhouse unless it's forecasted below about minus five degrees or maybe snowing. I essentially, I just leave them in pots outdoors in the corner of the garden somewhere. I completely forget about them.
I don't need to water them, don't need to do anything. When it rains, it rains, they'll get wet. And what happens is when the weather then warms in springtime, they'll have had their cold spell. And then in springtime, when it's still quite damp as well outside, they will germinate. So they'll germinate when they're ready. Okay? So that's just, it's just perfect. And you can just let mother nature do that. Now.
If you haven't been able to do that for some reason, maybe you've only just bought your seeds in the springtime, again, you can just pop them in the fridge and just do the same thing. So on the other hand, there are some other seeds which require warmth to germinate, or they'll at least just germinate quicker and maybe have a higher germination rate. So especially if you're starting seeds early in the year and they do require heat.
And it's best to check the seed packet on what the recommendation is. And I just use heated mats, just those plug-in ones, which you can buy online. They work wonders even in springtime. So not even early in the season, but even in spring when it's already starting to get warm, because it just speeds things up. It speeds up that germination. And what that can do is avoid bottlenecks in my germination area.
because I have a separate area where I do my germination with all my heat mats in and some lighting where I need it. And then I will move the seedlings once they've germinated into cooler conditions, which is what they need, slightly cooler. I'll then move them into the greenhouse. And by speeding up things in the germination area, because it's only quite small, my germination area, it just means that I can avoid that bottleneck. Okay, so the other variable.
that we can talk about today is light. So some seeds actually need light to germinate and some seeds need the darkness to germinate. So as a general rule of thumb, I tend to look at the size of the seeds. So the larger the seed, the deeper it needs to be buried, the more darkness it needs. And then the smaller the seeds, they just need to be more surface sowed or closer to the surface.
So some seeds will absolutely need light to germinate or dark to germinate, but your seed packets should tell you which ones they are. Okay, so just make sure that you read your seed packet before you start sowing.
So sometimes the seed packet will say just to surface sow something and maybe cover with maybe a light sprinkling of soil or vermiculite. And that's because the darkness will inhibit their germination. So it's just so important that you do read that seed packet before you start sowing. I can't tell you the number of times that I've buried my seeds quite deep and then I've looked at the seed packet to read that they need like to germinate. And scraping off the soil is
almost impossible. So there are also some seeds, and I'm talking specifically, probably lisianthus here, which require a lot of light to germinate and grow. So typically 16 hours, and this mimics their natural habitat. So in the UK, you definitely need grow lights to grow these because we typically sow these in November time.
when we only get nine to 10 hours of daylight. And that's just not enough for lisianthus. So grow lights are the trick. And I do have a blog all about growing lisianthus in the UK. So if that's something you want to do, I will pop the link to that in the show notes for you. So let's just take a moment to now think about water and oxygen. So these are the two non-negotiables for germination. Okay, without this,
nothing's going to happen. Okay, so water kickstarts the entire process and it does this by softening the seed coat and allowing the embryo inside to begin growing. And here's the thing, constant moisture can be one of the biggest challenges when it comes to successful seed germination. So picture this, you've really carefully sown your seeds and you're keeping an eye on them every day and then
A hot sunny afternoon sneaks up on you, those clouds disappear and that lovely moist compost you prepped so carefully, it can all dry out in a matter of hours. And if the seeds lose that consistent moisture at a critical moment in their development, it can just completely interrupt germination. So some seeds might stall, but others might just fail to germinate altogether.
So the number of times that I've sown, let's say two trays of seeds, and I've had them on different shelves in my greenhouse, but I've sown them at the same time, same potting mix, exactly the same seeds from the same packet. One has germinated and the other one hasn't. And I suspect it's because one of them has dried out more than the other at a critical moment. So it's really, really important to
to really keep an eye on soil moisture during those early stages. So seeds, they don't like to sit in soggy waterlogged soil, but they do need to be kept evenly moist. So think of it like a sponge, so damp, but not dripping. And here's my best tip for this. If you can use lids over the top of your trays, just those clear lids, I buy big ones that fit over the top of my trays, then that will help to keep in
the moisture, okay? And you can also use these in combination with a heated mat. So this will give you the absolute best germination rates and as quickly as possible. So another trick I often use for this is to actually sow my seeds inside a poly bag. So I've got some more information on this in my Seed Stratification blog.
I'll pop that link in the show notes for you. And I've also got one on growing or Laia grandiflora and there's another one on growing bells of Ireland. So I'll pop those in the show notes too because I use some of these tricks for those seeds as well. But essentially the method is really simple. So you'd wet a kitchen towel, just a paper towel. I just spritz mine with some water from a fine water sprayer and then sow the seeds on the top of the paper.
fold the piece of paper up a couple of times just to keep the seeds in place and then pop that inside the ziplock bag and place the bag somewhere warm indoors but not in direct sunlight, so preferably not on a sunny windowsill. Just check on it every few days and when you check on it and you unzip the bag you're also refreshing the oxygen inside the bag.
And as soon as each one germinates, can then pop them, you can pop them up individually. So this works really, really well for some really tricky seedlings like bells of Ireland and also parsnips. I would never sow bells of Ireland without using the baggy method. Last year I did sow my parsnips in the bags, but I also sowed them in the ground. And the ones which I sowed
in the bag came up and I got so excited when they came up in the bag. So a lot of people I know have real difficulty in actually getting their parsnips to germinate and it's a really great way of knowing that your seed is still viable. So you can try to germinate a handful of seeds using the poly bag method a few weeks before you actually want to sow your seeds outside in the ground to see if they'll germinate first. And if they don't, then you know they're not viable. You can chuck them and buy some more.
in time ready so that you can still sow them on time. So last year when mine germinated in the bag, I got very, very excited. I sowed quite a lot because I've had problems with them before too. So I sowed my, I won't say my whole batch, I'd already sown some outside in the garden and they just weren't germinating. So I sowed some more in my bag. And when they germinated, it was after about two weeks, my seeds in the ground had been,
in the ground for, in a raised bed for I think three or four weeks. And when I took my poly bag outside to go and sew them in the bed where I'd sewn them in the ground, I actually found the ones in the ground had also germinated. So I did get a double whammy last year, which was fantastic, but it's a really good way. If I'd have done that first and checked the germination first, I could have just saved myself the effort. But anyway.
So the next time you're sowing seeds, keep in mind that moisture, isn't just a nice to have, it's a deal breaker. So give your seeds the environment they need and they will thank you with those magical first green shoots. So if you're struggling to germinate a particular seed, I do encourage you to just do a little bit of research on its native habitat and just ask yourself.
Is this plant used to frosty winters or warm deserts or damp jungles? And from there, you can just mimic those conditions. So patience is key. Some seeds take a little bit more effort and time to coax into action, but the reward is worth it. And there's nothing quite like seeing those tiny green shoots emerge after all your hard work. So today's episode is a real shorty episode and that's it for today.
packed with top hints and tips though. So I hope that I've been able to demystify some of your sewing problems and give you the confidence to try again with any of those seeds that you might have failed with in the past. So do have another go, use my tips, do a bit of research, read your seed packets, have a look at my blogs, I'll link to them in the show notes because if you've been failing with some of those seeds then they'll give you a good tip.
And until next week, happy sowing and do let me know if you've got any seeds that you're stumped on that you're struggling with year after year, I would love to help. You can DM me on Instagram at The Hampshire Seed Company and I'm always happy to help. So goodbye until next week.