What to Sow in December: Seeds to Sow Indoors & Out This Month

December is the darkest month of the gardening year, and for most outdoor sowing it is a month off. But it is not a month with nothing to sow. The shortest days make December a turning point: the windowsill still produces fresh greens in a week, the coldest weeks are exactly what some hardy seeds are waiting for, and the slowest summer plants of all — begonias, geraniums and the hottest chillies — need a start before the new year if they are to flower and fruit on time. Here is what to sow in December, where to sow it, and what is better left until January.

• Windowsill sprouts, microgreens, cress & leafy herbs — ready in days to weeks
• With heat & light begonias, coleus, cacti, houseplants; from late December, geraniums & habaneros
• Outdoors hardy perennials & wildflowers that need frost, plus winter sowing in jugs
• December rule sow only where you can give light — or deliberately give cold

Why December sowing is different

In November there was still time for a last tray of sweet peas and a few winter leaves in the cold frame. In December, even that window has closed. Around the winter solstice, daylight in much of northern Europe falls to seven or eight hours — well below the 10-hour daylight rule, under which most plants barely grow. A seedling sown outdoors now simply waits for February.

That leaves three kinds of December sowing that make sense: crops harvested so quickly that light hardly matters; slow plants you raise under a grow light because they need five or six months to reach flowering size; and hardy seeds that actually need weeks of cold before they will germinate. Everything else is best sown in January or February, when the days are already lengthening.

On the windowsill: fresh greens in a week

The quickest harvest of the year comes from a jar or a tray. Sprouting seeds — mung bean, lentil, alfalfa, radish, rocket and broccoli — need no compost at all: rinse twice a day and eat them in three to six days. Our organic sprouting seeds are certified organic. On a tray of compost, microgreens such as pea shoots, mizuna, tatsoi, red mustard and daikon radish are ready to cut in 7–14 days, and cress on damp kitchen paper is ready in under a week. Our guide to growing microgreens and sprouts has the method.

For a pot of herbs, chives, parsley and coriander grow slowly but surely on a bright sill; basil really needs warmth and a grow light in December. See growing herbs indoors in winter for pots, watering and light.

With heat and light: the slowest summer plants

This is where December earns its place in the sowing calendar. Some summer flowers take so long from seed to bloom that a spring sowing only flowers in August. Sown in December or early January on a heated propagator at 20–24 °C, and grown on under a grow light for seedlings for 12–14 hours a day, they are bushy, budded plants by planting-out time in late May.

• Bedding begonias — Begonia semperflorens has seed as fine as dust and needs four to five months to flower. Sprinkle it on the surface of moist, fine compost, do not cover it (it needs light to germinate), and keep it warm under a clear lid. Expect seedlings in two to three weeks.
• Coleus — coleus is grown for its leaves, so you can start it any time you can give warmth and light. Surface-sow like begonias; December plants make large, colourful specimens for summer pots.
• Geraniums from seed — late December — zonal geraniums (Pelargonium) take 13–16 weeks from sowing to flower. Sow in the last week of December if you have a grow light, or in January on a bright windowsill.
• The hottest chillies — late December — habanero, Madame Jeanette, Dorset Pink and other Capsicum chinense varieties germinate slowly and need the longest season of all. They are the first chillies of the new season: sow at 25–28 °C in the last days of December or in January — but only if you can give them a grow light. Without one, a mid-February sowing catches up surprisingly fast. Ordinary sweet peppers and most other chillies and peppers can wait until February. Our guide to growing chillies from seed covers the whole season.
• Houseplants and exotics — houseplants, cacti and succulents, sensitive plant, bird of paradise, pink banana and agapanthus all germinate in steady warmth regardless of the season. They are slow, so winter is a good time to start them: you have time to wait.
• Climbers for next summer — passion flower and black-eyed Susan (Thunbergia alata) make bigger, earlier-flowering plants from a winter start. Soak passion flower seed for 24 hours first.

Outdoors: let the frost do the work

Many hardy perennial flowers and wildflowers carry a natural dormancy that only breaks after several weeks of cold, wet weather. December is an excellent month to sow them: in pots topped with grit, left outside against a wall, or as a winter sowing in milk jugs — the clear, ventilated containers act as mini greenhouses and the seed germinates on its own schedule in early spring. Our guide to perennials from seed and cold stratification lists which plants need the cold. Only sow outdoors when the compost is not frozen solid, and label everything: some of these pots will not show a seedling until March or April.

Your December sowing plan, in order

1. Start a sprouting jar this weekend Three to six days to the first harvest. Start a new jar every few days for a steady supply through the holidays.
2. Set up light and heat Put a heated propagator and a grow light on a timer before you sow the slow plants. Without both, wait until January.
3. Sow begonias and coleus first They need the longest run-up. Surface-sow, cover with a lid, keep at 20–24 °C and never let the compost dry out.
4. Sow the winter pots outdoors Perennials and wildflowers in gritty compost, or in milk jugs. Stand them where rain and frost reach them.
5. Add geraniums and habaneros after Christmas The last week of December is early enough for both — and only under a grow light; otherwise sow geraniums in January and habaneros in February.
6. Plan and order for January–February Sweet peas, onions, tomatoes, aubergines and the first broccoli follow soon. Use the quiet weeks to plan your vegetable garden and check old packets with a germination test — see how long seeds last.

Sow in December, or wait for January?

Common December sowing mistakes

• Sowing slow plants without a grow light. On a December windowsill, begonia and geranium seedlings stretch and flop. If you cannot add light, sow in January.
• Starting tomatoes too early. Tomatoes sown in December are leggy by March and no earlier to fruit. February is soon enough — see how to grow tomatoes from seed.
• Covering fine seed. Begonias, coleus and many houseplants need light to germinate. Press them onto the surface; do not bury them.
• Overwatering cool compost. In winter, wet compost plus low light is a recipe for damping off. Water from below and sparingly.
• Bringing cold-needing seed indoors. Perennials that need stratification will not germinate in a warm room. Leave the pots outside.
• Ordering too late. Popular varieties sell out early in the year. Order your January and February seeds in December.

Frequently asked questions

Can you sow seeds in December?
Yes, if you choose the right ones. Sprouts, microgreens, cress and herbs indoors; begonias, coleus, houseplants and exotics with warmth and light; and hardy perennials and wildflowers outdoors, where the cold helps them germinate.

What vegetables can I sow in December?
Outdoors, none that will crop before spring. Indoors, sprouting seeds, microgreens and cress give a harvest within days, and with heat and a grow light you can start the slowest chillies, such as habaneros, from late December.

Can I sow sweet peas in December?
You can, in a cold frame or unheated greenhouse, but there is little advantage. Plants sown in January under glass usually catch up with December sowings and are less likely to sit in cold, wet compost.

Is December too early to start chillies?
For most chillies and sweet peppers, yes — February is better. The exception is Capsicum chinense (habanero, Madame Jeanette, Dorset Pink), which is slow enough to benefit from a start at the turn of the year — provided the seedlings get a grow light. On a dim windowsill, wait until mid-February.

December sowing is small and satisfying: a jar of sprouts on the worktop, a lid of begonia seedlings under the light, and a row of frosty pots outside that will wake up in spring. If you are still looking for presents, our seed gifts for gardeners has twelve ideas they will actually use. Browse all our vegetable seeds, flower seeds and herb seeds, check the flower sowing calendar, or explore the rest of our growing guides.