Herb Seeds to Sow Indoors in Late Winter

Most people buy herbs as small potted plants from a garden centre, nursery or even a supermarket. However, with a little patience you can sow your own herb seeds indoors in late January or February for a fraction of the cost.

Home grown herbs will make you wonder why you ever bought bunches of sad looking herbs wrapped in plastic from the supermarket. Growing herbs from seed at home will not only save you money, it will also result in less waste, and give you an abundance of garden aromatics you can preserve for longer term storage.

The post below is written with newer gardeners in mind and focuses on herbs that are useful in everyday cooking, reliable to start indoors, and happy in a UK climate. We will look at basil, rosemary, thyme, and sage, covering how to sow, what conditions they need to germinate, and how to care for each plant through to maturity.

We will refer to a propagator which is clear (plastic or glass) cover for seed trays or pots that trap warmth and humidity to help germination. You can also get heated versions which provide gentle bottom heat. Heated propagators are great, but don’t fret if you don’t have one. Popping your seed pot or module tray in a clear plastic bag (a food zip lock bag is fine) and keeping it on a sunny window sill should suffice. Many seeds like to soil warmer at this time of year, so bring your seed compost indoors a few days before planting. This will allow the compost to warm up a bit and result in happier seeds.

You’ll also see references to succession sowing (sowing small batches at intervals so you always have fresh plants coming along) and transplanting (moving plants on into larger pots or outside once conditions are right). Both are simple, practical techniques that quickly become second nature.

General Setup for late winter Sowing

Before we dive into individual herbs, it’s worth getting the basics right.

You will need:

• Seed trays or small pots (2–3 in / 5–7.5 cm) deep
• Multi‑purpose compost or seed compost
• A warm sunny windowsill
• Clear plastic bags or a clear lid (for humidity) or heated propogator

Light & warmth: In January/February, light levels are low. A bright windowsill is ideal. Most herbs germinate best at approximately 10 –21°C. (60–70°F). The best advice for seed germination temperatures will be written on each seed packet.

Watering: Keep compost damp, not wet. Overwatering is the quickest way to lose seedlings. Seeds can get mouldy if they are too wet.

Humidity trick: For slow or fussy germinators, loosely place a clear plastic bag over the pot or seed tray to trap humidity. Remove it as soon as seedlings appear. This is a good idea for most seeds started indoors at this time of year such as chillies or aubergines (Eggplant). Unless of course you have a heated propagator.

See here for seeds to sow in late January What Vegetable Seeds to Sow in Late January: A planting Guide for Beginners

Basil (Ocimum basilicum)

Good varieties for the UK

• Genovese – classic Italian basil, excellent for pesto
• Sweet Green – reliable and fast growing (high notes of mint & clove)
• Greek (Bush) Basil – compact, ideal for windowsills (smaller leaves – strong flavour)

How to sow

• Sow seeds ¼ in (0.5 cm) deep
• Space seeds about 1 in (2.5 cm) apart
• Lightly cover and gently water

Basil needs warmth to germinate, ideally 18–24°C. (65–75°F) A plastic bag or propagator lid is very helpful here.

Germination

• Time: 5–10 days
• Remove plastic cover as soon as seedlings emerge

Growth and repotting

Basil grows quickly. Once seedlings have 2–3 true leaves, thin them out or pot on into 4–5 in (10–12.5 cm) pots. Basil dislikes having cramped roots.

True leaves are the first set of leaves that appear after the initial seed leaves. The true leaves will look the same as the leaves on a mature plant. The seed leaves will show first and are generally smaller. If you are unsure check with the picture on your seed packet or do a quick internet search. You can also wait until you have more than 2 true leaves. It won’t be the end of the world if you don’t pot on until you have 3 or 4 leaves.

If you have 3 or 4 true leaves before it’s time to plant outside then just transplant to a slightly larger pot until it’s time to plant out – around April/May or after your last frost date.

Succession sowing

Highly recommended. Sow a new batch every 3 – 4 weeks to ensure a constant supply.

Rosemary (Salvia rosmarinus)

Rosemary is native to the Mediterranean, where it grows in poor, well‑drained soils and plenty of sun. Understanding this makes its preferences much easier to meet indoors.

Good varieties for the UK

• Common Rosemary – hardy and reliable
• Miss Jessopp’s Upright – neat growth, good for pots
• Tuscan Blue – strong flavour, vigorous once mature

How to sow

• Sow seeds on the surface and lightly cover with compost
• Use small pots rather than trays

Rosemary prefers slightly cooler conditions than basil, around 15–18°C (60–65°F)

Germination

• Time: 14–28 days (sometimes longer, so be patient)
• A plastic bag helps retain humidity, but sure there is some ventilation.

Growth and repotting

Rosemary grows slowly. Seedlings can stay in their original pots for several months. Repot only when roots clearly fill the pot.

Ongoing care

• Plenty of sunlight
• Allow compost to dry slightly between watering. Rosemary doesn’t like soggy roots.
• Avoid high humidity once established, so remove any plastic bag covers

Succession sowing

Germination can be uneven, so sowing a second pot as backup is sensible.

Thyme (Thymus vulgaris)

Thyme also originates from the Mediterranean region, thriving in sunny, dry conditions. This heritage explains why it prefers good drainage and dislikes being overwatered.

Good varieties for the UK

• Common Thyme – versatile and hardy
• Lemon Thyme – fresh citrus flavour
• English Thyme – reliable for cooking

How to sow

• Sow on the surface
• Press seeds gently into compost
• Don’t bury the seed too deeply into the compost

Germination

• Time: 10–21 days
• Best temperature: 15–21°C (60–70°F)
• Plastic bag useful until germination, once the seeds show a few millimetres above the soil, change the plastic bag for a propagator lid.

Growth and repotting

Thyme stays small and doesn’t mind being slightly root‑bound. Pot on only when growth slows noticeably.

Ongoing care

• Sunlight light is essential
• Water sparingly
• Trim lightly to encourage bushiness

Succession sowing

Resow if germination is patchy.

Sage (Salvia officinalis)

Sage is native to the Mediterranean and Balkan regions, where it grows as a hardy, shrubby perennial. It adapts well to UK and cooler climate well once established.

Good varieties for the UK

• Common Sage – classic culinary variety
• Broad‑Leaved Sage – excellent flavour
• Purple Sage – ornamental and edible

How to sow

• Sow seeds ¼ in (0.5 cm) deep
• Space well, as seedlings grow steadily

Germination

• Time: 10–21 days
• Temperature: 15–21°C (60–70°F)
• Plastic bag helpful in early stages

Growth and repotting

Sage seedlings are sturdy. Pot on once roots fill the container. Avoid oversized pots early on as you risk over watering. Sage can be potted on a number of times into sequentially larger pots as the plant develops. Just be careful you don’t damage the roots when repotting – gently does it!

Ongoing care

• Plenty of light
• Moderate watering
• Good air circulation prevents mildew

Succession sowing

Optional. Sage is long‑lived, so one or two healthy plants are usually enough.

When to Move Herbs Outdoors

From late April to May, herbs can be hardened off and moved outside once frost risk has passed. Start by placing them outdoors for a few hours a day, gradually increasing exposure.

When I first plant outside I make sure the new plant is protected form slugs, snails and other beasties until it becomes more established. I will generally use little closh or some netting.

Final Thoughts

Growing herbs indoors in January is about small steps and steady progress. Not every seed will germinate, and that’s normal. Succession sowing, patience, and observation are the to turning those tiny seeds into a fruitful herb bed that can be utilised in any kitchen or medicinal cabinet.

Let me know in the comments what your favourite herbs are in the garden.

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