By Anna, founder of Gardeners Box
A seed tray in December needs a reason to exist. Otherwise it’s another thing to move out of the way when someone needs the windowsill.
There are flower and plant seeds you can sow in December in the UK, but this is a selective month. Some specialist seeds benefit from winter conditions. Many other packets are better left closed until their recommended sowing season. I’d rather give you a small, useful choice than an impressive list of plants that need equipment you haven’t got.
This guide covers a patient seed project, established plants you can put into suitable ground, and the young plants already asking for a little attention. The flower photographs show what mature plants can look like in season, rather than a promise of flowers from a December sowing.
Start with the instructions on the packet
Look for a seed packet that specifically recommends winter sowing or a cold, moist period before germination. This treatment is often called cold stratification. It means keeping the seed moist and cool for the time the particular plant requires, rather than simply putting a dry packet in the shed.
Alpine plants vary enormously. Some need cold, some have different requirements, and some can take a long time to germinate. A photograph of a mountain flower tells you very little about its seed instructions. Buy from a supplier that gives a clear method for the named species.
You’ll also need somewhere to keep the pot afterwards: a sheltered cold frame or a suitable spot protected from persistent heavy rain, with ventilation and regular checks. An unheated greenhouse is not frost-free, and a heated propagator won’t provide a cold treatment.
Gentian seeds for gardeners who can wait
Gentians make a lovely longer project if you enjoy watching a labelled pot with very little happening in it. Those blue flowers are persuasive, but they are a later reward. Germination can be slow and uneven, and flowering takes longer again.
Choose seed with instructions that explicitly call for a cold, moist period or winter sowing. Follow those instructions for the species, including any temperature changes, covering and timing. Don’t assume all gentians need exactly the same treatment or soil conditions.
- Use a clean pot with drainage holes and the free-draining seed compost specified by the supplier. Moisten it and allow excess water to drain.
- Sow and cover the seed as directed. Some small seed needs very little covering, so resist the urge to bury everything under a generous blanket of compost.
- Label the pot with the exact plant name, sowing date and any treatment dates. Future you will be grateful for more than “blue flowers”.
- Put the pot in the recommended conditions, protected from heavy rain that could wash seed away or saturate the compost. Keep it moist without leaving it standing in water, and check it regularly.
- Follow the next stage of the instructions after the cold period. When seedlings appear, give them suitable light, ventilation and careful watering. Move them on according to their size and the supplier’s guidance.
Allow weeks or months, sometimes longer, rather than setting a Christmas deadline. Check the expected germination period before giving up on an apparently empty pot. There is no prize for tipping it out the day before something emerges.
If keeping track of this sounds like a chore, leave specialist sowing for another year. Your garden can manage perfectly well without a winter propagation experiment.
Plant hardy cyclamen for a sheltered corner
For a planting job, consider established hardy cyclamen bought in pots. Choose plants clearly labelled as hardy outdoors and suited to your site. Florists’ indoor cyclamen are a different purchase, so check the label before leaving a pretty pot out in the frost.
Hardy cyclamen generally suit partial shade and humus-rich soil that drains freely. Choose their position carefully, following the particular plant’s instructions. Waterlogged ground is a poor winter home, however good it looks on a mild afternoon.
Plant at the level they were growing in the nursery pot, unless the supplier directs otherwise. Water in, then check moisture rather than watering automatically. Leave the job until conditions improve if the ground is frozen or sodden.
Flowering times vary by species. The plants in the photograph illustrate hardy cyclamen in bloom; they are not a guarantee of a December display. This is about planting established plants. It is not a recommendation to sow cyclamen seed now for instant winter flowers.
Look after the flower seedlings already under cover
On a mild day, give the greenhouse or cold frame some air, then close it again before temperatures drop. Clear decaying leaves from around small plants and check for slugs and damage. Shelter is helpful, but it does not remove the need to look.
Feel the compost before watering. Cool plants growing slowly use less water than a busy tray in spring, and crowded, damp foliage can cause trouble. Space pots so you can inspect them without knocking half the shelf over.
Keep protected plants in the best suitable light you can offer. Turning up the heat will not compensate for a dim corner. If growth is pale and stretched, review the conditions before adding another sowing to the problem.
Put spring flowers on paper first
Sort the packets you already own by their recommended sowing window. Note which need warmth to germinate, which need protection afterwards and which can wait for outdoor sowing. Check how many pots your space can hold once seedlings need room of their own.
That last bit is easy to overlook. A packet fits in a drawer; its seedlings may take over a shelf. Choose the plants you have room to grow on, and leave some space for moving things when the weather changes.
If all you do this month is label a specialist sowing and keep your existing plants healthy, that counts. What have you got growing under cover? Tell me in the comments.
For something edible to grow indoors, plus suitable outdoor planting, read our December vegetable and fruit guide.
Example box shown. Seed selections change each month.
A growing project to look forward to each month
Fancy keeping a little growing going through the year? Gardeners Box delivers eight seasonally chosen seed varieties each month, with a printed growing booklet and wooden plant markers to help you get started. A lovely thing to open for yourself, or a gardener you know.
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