January in the UK is very much a “behind the scenes” gardening month, but there is plenty you can be getting on with if you want to take the chance. With soil cold, wet and often frozen, most vegetable seeds need significant protection, warmth and good light to get going. With last frost dates in the UK falling somewhere between late April and late May depending on region, anything sown now will have to spend a good while indoors or undercover before they can be planted out. The key is to match each crop to the right conditions: warmth for germination, steady moisture, and enough light to prevent weak, leggy growth.
In this blog we will look at what seeds you might want to start in January and the conditions needed to keep them healthy until planting out time. Before we start, I do need to say that planting in January is not essential and you shouldn’t feel pushed into planting seeds early. You have plenty of time and it’s not the end of the world if you wait a few more weeks or even a month or so. You do you 😊
And don’t forget to always label you seeds whatever you are planting see ‘Labelling: simple but vital ‘ for guidance on labelling your sowings.
Chillies, sweet peppers and aubergines can be sow early as they need a long growing season. Sow seeds about ¼ inch (0.5 cm) deep in small modules or seed trays filled with fine, free-draining compost. They germinate best at 21–27°C, (70–80°F) so make sure the seeds have a heat mat, an airing cupboard or warm shelf ideal until shoots appear, this is usually in 7–14 days. Once you have visible shoots move them into bright light. A south-facing windowsill or under grow lights will be fine. Keep compost just moist rather than wet. These plants will stay indoors until after the last frost and are usually planted outside or into an unheated greenhouse in late May or even early June, once nights stay above 10°C (50°F). This means your plants will need to stay indoors for some time, so will need attention to ensure they don’t get cold or leggy. From the first shoots to outside ready I generally wrap mine in some fleece at night as the temperature in the house drops overnight. During the day I keep I keep a them under a plastic closh which covers the seed tray, and keeps them in their own wee microclimate.
Onions, leeks and early salad crops like winter lettuce can also be started in January. Onions and leeks are best sown thinly in trays, covering seeds with about ½ inch (1 cm) of compost. They germinate in 10 –14 days at around 10 –18°C. (50 – 65°F) and don’t need a heat mat, they should be fine on a windowsill in a seed tray with a closh/ clear plastic lid or in a frost-free greenhouse. Even in a greenhouse I would also use a plastic or glass closh or cover to add further protection. Keep compost evenly moist and give them as much light as possible. They’ll grow slowly at first, producing grass-like leaves, and can be planted out from March or April once soil is workable and no longer waterlogged. Lettuce can be sown shallowly, barely covered with compost, as it needs light to germinate, and will sprout in 7–10 days in cool but bright conditions.
If you have a sheltered garden or heavy protection such a fleece, there are a few seeds that can be sown direct even in January. Broad beans are the standout option. Choose hardy varieties such as Aguadulce, and sow seeds 2 inches (5 cm) deep and 6 inches (15 cm) apart into soil that is not frozen and drains well. A cloche (row cover) or fleece is strongly recommended to protect seedlings from frost and birds. Broad beans germinate slowly in winter, often taking 2–3 weeks, and growth will be minimal until days lengthen. They prefer cool conditions, need little extra watering at this time of year, and benefit from soaking seeds overnight to speed germination.
Peas can also be started now, but are usually more reliable under cover. Sow them in deep modules or small pots, about 1–1½ inches (3 – 4 cm) deep, and keep them in an unheated greenhouse or cold frame. They germinate in 10–14 days at cool temperatures and don’t need much heat, just protection from hard frost. Light is important to keep growth sturdy, and watering should be modest. Seedlings can be planted out from March, depending on soil condition, with protection if cold weather returns. My best advice is to have a closh at the ready even when planted out and keep a good eye on the weather for colder snaps
Across all January sowings, water lightly but consistently. Cold, wet compost is the fastest way to lose seedlings. Good drainage is essential, especially for indoor sowings, and bright light after germination is just as important as warmth before it. Soil outside should only be used if it crumbles easily in the hand rather than sticking together, a sign it’s ready to work. By starting the right vegetables now, using windowsills, airing cupboards, heated pads, grow lights or heated greenhouses or cloches as needed, you set yourself up for strong, healthy plants that are ready to thrive once spring truly arrives.
You can also start chilli seeds in January. Sow them indoors as it’s far too cold outside not even an outside closh or heated greenhouse will be warm enough for the seeds to germinate. Use small pots or a seed tray filled with seed compost (seed-starting mix), lightly press the seeds onto the surface and cover them with a thin layer of compost. To give them the warmth they need, place the pots on a heated propagator or heat mat, aiming for a constant 22–28°C (72–82°F) and use grow lights (plant light) to make up for short winter days, keeping the compost just damp, not wet. They need both light and heat to germinate. Clear lids or plastic covers help retain moisture until seedlings appear, after which keep young plants warm, well lit, and frost-free. One of the biggest problems with planting chillies in January is that the plants can become leggy, so it might be worth considering waiting until late Feb for this one.
If you are looking for a video demonstrating some of the equipment mentioned in this post Jessie at Plot 37 has an excellent guide to her indoor set up. The set up starts around 14 mins into the vid. However, I have no doubt you will find some if not all the information in her vid useful My DIY Indoor Grow Setup for New Year Chilli Sowing!
January Sowing Quick Reference Guide
Chillies, Sweet Peppers & Aubergines
- Where to sow: Indoors under cover
- Containers: Modules or seed trays
- Depth: ¼ inch (0.5 cm)
- Germination time: 7–14 days
- Heat needed: High 21–27°C (70–80°F)
- Light: Very bright once sprouted (windowsill or grow lights (shop lights, daylight lamps)
- Water: Light but consistent, never waterlogged
- Soak seeds first: Optional, can speed germination
- Plant outside: Late May–June, after last frost
Onions
- Where to sow: Indoors or frost-free greenhouse
- Containers: Seed trays
- Depth: ½ inch (1 cm)
- Germination time: 10–14 days
- Heat needed: Low 10–18°C (50–65°F)
- Light: Bright but cool
- Water: Even moisture
- Soak seeds first: Not needed
- Plant outside: March–April when soil is workable
Leeks
- Where to sow: Indoors or under cover
- Containers: Seed trays
- Depth: ½ inch (1 cm)
- Germination time: 10–14 days
- Heat needed: Low
- Light: Bright, cool conditions
- Water: Moderate
- Soak seeds first: Not needed
- Plant outside: April–May
Winter Lettuce
- Where to sow: Indoors, cold frame or cool greenhouse
- Containers: Trays or shallow modules
- Depth: Surface sow, barely covered
- Germination time: 7–10 days
- Heat needed: Cool conditions
- Light: High (needs light to germinate)
- Water: Light and regular
- Soak seeds first: No
- Plant outside: March onwards under protection
Broad Beans
- Where to sow: Direct outside or under cloche
- Containers: Direct sow or deep pots
- Depth: 2 inches (5 cm)
- Spacing: 6 inches (15 cm)
- Germination time: 14–21 days
- Heat needed: None
- Light: Natural daylight
- Water: Minimal in winter
- Soak seeds first: Yes – overnight recommended
- Plant outside: Already in position
Peas
- Where to sow: Under cover or cold frame
- Containers: Deep modules or pots
- Depth: 1–1½ inches (3–4 cm)
- Germination time: 10–14 days
- Heat needed: Low
- Light: Bright to prevent leggy growth
- Water: Light, avoid soggy compost
- Soak seeds first: Helpful but optional
- Plant outside: March with protection
Chilli
- Where to sow: Indoors under cover (heated propagator or warm room)
- Containers: Small pots, seed trays, or modules
- Depth: Surface sow, lightly covered with compost (about ¼ inch / 0.5 cm)
- Germination time: 7–21 days
- Heat needed: High 22–28°C 72–82°F)
- Light: Very bright; grow lights recommended to prevent leggy growth
- Water: Light and regular; keep compost damp, not soggy
- Soak seeds first: Optional, can potentially speed up germination
- Plant outside: May – June after last frost, harden off first
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