Winter Sowing UK: A Beginner's Guide to Growing Seeds in Milk Bottles

Empty milk bottles.

A bag of compost.

A few packets of seeds.

And the coldest, wettest, most miserable months of the year.

It doesn't sound like the start of a garden, does it?

But that's exactly what winter sowing is.

You sow your seeds outside in the middle of winter, in little homemade greenhouses, and let the weather do the rest.

So here's a beginner's guide to winter sowing in the UK: what it is, which seeds to use, how to turn milk bottles into mini greenhouses step by step, and what it costs to get started.

What Is Winter Sowing?

Winter sowing is a way of starting seeds outdoors between roughly December and February.

Instead of sowing indoors, you sow into see-through containers with a lid, like a plastic milk bottle cut in half.

They sit outside all winter.

They get rained on, frozen, thawed and frozen again.

Lots of hardy seeds need a spell of cold before they'll germinate.

Gardeners call this cold stratification.

Normally you'd fake it by popping seeds in the fridge for a few weeks.

Then, as the days get longer and warmer in spring, the seeds sprout when they're ready.

The idea has been around for years, but it's had a big boost lately, with gardeners sharing their rows of taped-up milk bottles all over TikTok and Pinterest.

It's one of the cheapest ways I know to grow a lot of plants.

Why It's So Good for Beginners

I love anything that makes growing your own a bit less faffy.

And this is about as low-faff as seed sowing gets.

• No indoor space needed. Your windowsills stay free and you don't need a propagator or lights

• The seedlings are tough from day one. They grow up outside, so hardy plants don't need hardening off

• Less watering. The lids hold the moisture in, and rain gets in through the top

• Fewer leggy seedlings. They get proper daylight instead of stretching towards a window

• It uses up rubbish. Milk bottles, juice bottles and clear food tubs all get a second life before they go in the recycling

What You'll Need

You've probably got most of this already.

• Clear or white plastic milk bottles, rinsed (the 4 pint ones are ideal)

• Seed compost or multi-purpose compost

• A sharp craft knife or strong scissors

• Something to make holes, like a skewer or a small drill bit

• Duct tape, because ordinary sticky tape won't survive the weather

• Plant labels and a pencil, plus a paint pen or permanent marker

• A tray, crate or old box to stand the bottles in

• Seeds, of course

The Best Seeds for Winter Sowing in the UK

The trick is choosing seeds that can cope with the cold.

Look on the packet for words like "hardy", "hardy annual" or "hardy perennial", or anything that says it can be sown in autumn or needs a cold period.

Hardy perennials (sow December to February)

These are the ones that really love it, because many of them need the cold to germinate at all.

• Foxgloves

• Echinacea

• Aquilegia (granny's bonnets)

• Lupins

• Sweet William

• Verbena bonariensis

• Hollyhocks

Hardy annual flowers (sow January to February)

• Calendula

• Cornflowers

• Nigella (love-in-a-mist)

• Poppies, including California poppies

• Larkspur

• Sweet peas

Hardy vegetables (sow February to March)

• Kale

• Cabbage

• Leeks

• Onions and spring onions

• Lettuce

• Spinach

What to wait on

Tender plants can't cope with frost, so don't sow these in winter:

• Tomatoes

• Courgettes and squash

• Peppers and chillies

• Basil

• Cosmos and zinnias

You can use exactly the same milk bottle method for these later on, from around April, once the worst of the frosts have passed.

Some people call that spring sowing.

How to Winter Sow in Milk Bottles

Step 1: Clean your bottles

Rinse each bottle well with warm, soapy water and peel off the label if you can.

Take the lid off and put it in the recycling.

You won't be putting it back on. The open top lets rain in and lets air out.

Step 2: Make the drainage holes

Poke four to six holes in the bottom of each bottle.

Drainage really matters.

Without it, the compost turns into a soggy, frozen block and the seeds rot.

A few small holes around the top half helps with air flow too.

Step 3: Cut the bottle in half

Cut around the bottle about 10 to 12cm up from the base.

Leave a small section uncut just under the handle, so the top flips open like a hinge.

Go carefully with the knife. Milk bottles are slippery things.

Step 4: Fill with damp compost

Wet your compost first in a bucket, until it feels like a wrung-out sponge.

Then fill the bottom half of the bottle, about 7 to 10cm deep.

Give it a gentle press so there are no big air pockets.

Step 5: Sow your seeds

Sprinkle the seeds over the surface and cover them to the depth it says on the packet.

Tiny seeds like foxgloves just sit on top.

Bigger seeds like sweet peas get pushed in about 1cm deep.

Don't worry too much about spacing.

Lots of winter sowers grow their seedlings in a clump and split them up later.

Step 6: Label it twice

Put a plant label inside, written in pencil.

Then write on the outside of the bottle too, with a paint pen or permanent marker.

Writing on the outside fades in the sun and rain.

By April you won't have a clue which bottle is which if you only do one.

Step 7: Tape it shut

Close the top and run duct tape all the way around the cut.

Make sure it's sealed properly, so it doesn't pop open in the wind.

Step 8: Put them outside

Stand the bottles somewhere that gets sun and rain.

Not under the eaves of the house, and not in the greenhouse, because they need the rain coming in through the top.

Grouping them together in a tray or crate helps them hold each other up.

If you're somewhere windy, weigh the crate down.

On the Scottish coast, an empty milk bottle would be halfway to the next village in one decent gust.

Then leave them be.

That's it.

Looking After Your Winter Sown Seeds

The good news is there's very little to do.

• Check them every couple of weeks. If the compost looks dry inside, give it a little water through the top

• Don't panic if they freeze solid. That's normal, and part of the process

• Snow is fine. It sits on top like a blanket and melts in as water

• Be patient. Some hardy perennials won't show until April or May, especially further north

• Open up on mild days. Once seedlings appear and the weather warms, untape the top on sunny days so they don't overheat, and close it again if a frost is forecast

• Take the tops off completely once the seedlings are touching the lid and the frosts are mostly over

When to Plant Them Out

Your seedlings are ready to plant out when they've got a few sets of proper leaves and look sturdy.

Because they've grown up outside, hardy plants don't need hardening off.

You can plant them straight into the garden.

If you sowed in a clump, either tease the seedlings apart gently or cut the whole block into little squares, like a tray bake, and plant each chunk.

The chunk method is quicker, and the roots barely notice.

In Scotland the last frosts can come quite late, so keep an eye on the forecast before planting out anything delicate.

A few old milk bottles.

A bit of tape.

And by spring, a garden's worth of seedlings that grew up tougher than anything on a windowsill.

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You'll notice that the images across my blog are a mixture of my own photography and AI-generated images.

I'm a one-woman band running this little corner of the internet, without a team of photographers, designers or editors behind me. Living with OCD also means I can be particularly careful about things like copyright and image permissions, so I sometimes use AI to help bring my ideas to life without those additional worries.

Where possible, I love sharing my own photographs, especially glimpses of my cottage, garden and everyday life here in Scotland. Other times, I'll use AI-generated imagery to illustrate an idea or provide a little creative inspiration.

I believe in being transparent, so I wanted you to know that you'll find a mixture of both throughout my website. The words, experiences, opinions and ideas are my own.

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