My Gardening Journey

Missed the early sowing window? This is the UK catch-up guide. It tells you what is still worth sowing indoors. Learn what to sow outside instead. Discover when to buy plug plants. Find out how to stop wasting weeks on doomed sowings.

For the comprehensive indoor sowing technique, check out this guide. It includes propagator settings, compost, and pricking out. This post is different. It is the “I’m behind, what now?” decision system.

Over the years I’ve found life events, failed germination and the weather can impact when I start to sow. Sometimes I’m left frustrated with myself but I’ve learned that gardening should be enjoyable, and not chasing perfect. Below are ways I have managed to still have a great year when I’ve started later than I hoped.

Decide if indoors is still worth it

Late sowing often works because plants grow faster once days are longer and temperatures are higher. The problem is not “late” in general. The issue arises when starting a crop that needs a long season. This leads to running out of time before it can flower and crop properly.

Use this simple test:

1. Is it a long-season, warm-loving crop? Tomatoes, peppers and aubergines usually need a long run of warmth. If it is late March or later, and you do not have consistent heat, treat these as “buy plugs” crops. This is especially important for long-season crops.
2. Does it hate root disturbance? Most root crops (carrots, parsnips, beetroot) are better direct sown. Starting them indoors is usually a false economy.
3. Can you harvest it in 6–10 weeks? If yes, it is a perfect catch-up crop. Think salads, radishes, quick herbs, dwarf French beans, and cut-and-come-again leaves.

Before you sow anything, reduce wasted time by checking seed viability. If you are unsure about an older packet, test if old seeds are still usable. Sow only what is likely to germinate.

Helpful references: RHS has a clear baseline on how to sow seeds indoors. For seasonal timing mindset (and avoiding sowing too early), Charles Dowding’s sowing timeline is a useful reality check.

Pick your month catch-up plan

If you only read one section, read this. Choose the line that matches where you are right now, then use the decision table below to fill the gaps.

• February to mid-March: you can still start many long-season crops if you have warmth and light. If you do not, focus on hardy module sowings and get your space ready. This is also a good time to plan plug plants for anything you know you will be late for.
• Late March to April: switch mindset from “start everything” to “start what is quick”. Begin tender indoor sowings that require only a few weeks under cover. Prepare for direct sowing outdoors as soil warms.
• May: you are not too late. You are in prime growing speed. Sow tender crops indoors only if they benefit from a short head start, and direct sow fast crops outdoors. For long-season crops, buy healthy plugs and move forward.
• August to September: start again for autumn and winter salads. Many leafy crops prefer cooler nights and are less likely to bolt.

Choose the right late indoor crops

Late indoor sowing works best when the crop is fast, tender, and benefits from a short protected start. Think “two to four weeks under cover”, not “months on a windowsill”.

• April to early May indoor starters: courgettes, squash, pumpkins, cucumbers, sweetcorn, French beans. Sow them close to your planting-out date so they do not sit around getting stressed in small pots.
• Quick modules under cover: Lettuce and salad mixes are ideal. Include spring onions, and brassicas for later planting. This is useful if you are tight on space outdoors.
• Warmth lovers (usually not worth late seed sowing): tomatoes, peppers, aubergines. If you are late, treat these as “plug plant” crops unless you have strong heat and a long season.

If you want inspiration for fast varieties, Suttons has a useful overview. These plants still earn a harvest after a late start. It lists fast-growing vegetable seeds for summer. Use it as a “switch crop” shortlist, not a shopping list.

Switch to direct sowing when soil warms

Direct sowing is the late-sower’s superpower. As soil warms through spring, many crops grow better when sown in place, with no transplant check.

• Always direct sow: carrots, parsnips, beetroot (best results come from sowing where they will grow).
• Perfect for succession sowing: radish, rocket, salad leaves, spinach. Sow little and often for a steady harvest.
• Good direct sow options once conditions are right: peas and beans (avoid cold, waterlogged soil).

If you want a month list, use it as a cross-check. Do this instead of duplicating it here: what to sow in March.

Use plug plants as a smart shortcut

Plug plants are not “cheating”. They are a time trade. If you have missed the best seed-start window for long-season crops, use plugs. This is usually the best way to protect your harvest.

• Best as plugs when you are late: tomatoes, peppers, aubergines, chillies, celery, leeks, many brassicas.
• What to look for: compact plants, healthy colour, no pale stretching, roots not tightly circling the pot.
• How to recover lost time: pot on quickly if needed, then harden off and plant out at the right moment.

For a “not too late” framing, Unwins’ guide to seeds to sow in May serves as a useful external reference. This avoids turning it into a month list.

Late-summer indoor sowing for autumn salads

August and September are ideal for restarting under cover. Warm days help fast germination, and cooler nights reduce bolting. This is where indoor sowing earns its keep again.

• Great August–September module starts: winter lettuces, rocket, spinach, chard, mizuna, mustard leaves, lamb’s lettuce, spring onions.
• Where they go: greenhouse beds, polytunnel, cold frames, or containers on a sheltered patio.
• Goal: steady pickings through autumn, and a longer season if you can protect from hard frost.

If you want the full deep guide (varieties, protection, harvest windows), use: grow winter salads in the UK.

Avoid the common late-sowing traps

Late sowing usually fails for boring reasons. Light, heat, pot size, and timing. Fix those and you will be surprised how much catches up.

• Leggy seedlings: caused by low light and too much warmth. Use the brightest spot you have, keep seedlings cooler, and avoid forcing growth. If this is a recurring problem, use prevent leggy seedlings to fix the setup.
• Overgrown modules: late-sown seedlings grow quickly. Pot on early if roots fill the cell, or sow later so plants are the right size at planting-out time.
• Wrong crops indoors: root crops and very fast greens often waste time indoors. Direct sow them instead.
• Clinging to impossible crops: if you are late for long-season warmth lovers, buy plugs and move on.

Catch-Up Decision Table

This table is the fastest way to decide what to do next. Pick your category, then act.

Mini table: August–September indoor starts for autumn and winter cropping

Conclusion

If you are behind, you do not need a perfect plan. You need a fast decision. Pick crops that match the season. Switch to direct sowing when it makes sense. Use plug plants for anything that needs a long run. Restart in late summer for autumn salads. Do that, and “too late” becomes “still productive”. Check out our guide to hardening off seedlings for when you are getting ready to plant them out.