Stop planting seedlings straight from the windowsill.
Indoor seedlings are soft, and sun and wind shrivel them. A week of half days outside first.
Seedlings raised on a windowsill or under cover are soft, and planted straight into full sun and wind they can shrivel, stall or die. Harden them off first: a week, up to two, of increasing time outside, starting with a few hours of gentle morning light and building to full days. Keep the water up, plant out in the cool of the day once the soil holds 16°C for tomatoes and the warm end of that range for capsicum and chilli, and give basil the longest wait of all.
The tomatoes were sown in August on the kitchen windowsill and turned every day. By late September they are 10 centimetres tall and the first warm weekend arrives, so out they go, into the bed, into the sun, and by Monday the leaves are bleached and curled. They were not bad seedlings. They were soft seedlings, and the correction is a week of half days.
Why windowsill seedlings shrivel outside
Seedlings raised indoors, on a sill or under cover have never met wind, direct sun or a cold night, and their growth is soft. Gardening Australia's Millie Ross describes hardening off as reducing the shock a plant gets when it goes from a molly-coddled environment straight to the open vegie patch. Sophie Thomson says the same of bought punnets: from a shop, glasshouse or shade house they are likely to be a bit soft and need to harden up before planting, so give them the same week or so. The fix is not a product. It is time.
The week of half days
Hardening off is about a week, up to two, of getting the seedlings used to outside in stages. One workable schedule, drawn from ABC Organic Gardener's Justin Russell and Gardening Australia's Jane Edmanson:
- Day 1 to 2: a few hours outside in a sheltered spot, in gentle morning sun or filtered light, then back under cover.
- Day 3 to 4: half to three quarters of the day outside.
- Day 5 onward: full days outside.
- Once nights are mild and no frost is forecast, a night or two outside before planting.
- Frost, a gale or a storm in the forecast: bring them under cover and pick up where you left off.
Keep the water up. Pots dry out far faster outdoors than on a sill, so check them daily and never let them wilt; a seedling that dries out even once can be lost. Water when the top of the mix is dry rather than on a fixed schedule. Many growers also skip the liquid feed for the week so the growth stays tight rather than soft.
Leggy seedlings, and what to do with them
Windowsill seedlings lean to the light and stretch. Turn the tray daily and give them the brightest spot you have. Leggy tomatoes are forgiving: strip the lowest leaves and bury the stem to just below the first leaves when you plant, and it grows roots along the buried section, which is why Gardening Australia and Sustainable Gardening Australia both recommend planting tomatoes deep.
Capsicum and chilli do not root along the stem as readily, so plant them at the level they were growing and fix legginess with light and a bigger pot instead. They are slower off the mark in any case, 10 to 20 days to germinate against 7 to 10 for tomatoes, and they need warmth to sprout. Pot them on once they have their first true leaves and hold them under cover until the soil is properly warm; cold soil can set them back for the whole season.
When they are ready, and when the bed is
A seedling is ready to plant when it has at least a couple of sets of true leaves and stands roughly 10 centimetres tall. Tomatoes get there four to eight weeks from sowing. The root ball should slide out of the pot intact; roots matting the surface and a punnet that feels rock hard when squeezed mean they are overdue.
The bed has its own test. Tomatoes go out after the last frost and once the soil holds 16°C, and 18 to 20°C is better. Capsicum and chilli want the warm end of that range and go out last. Basil is the sook of the group: in cold soil it sulks and one frost kills it, so plant it a couple of weeks after the tomatoes, once nights are reliably mild. Our kitchen thermometer test covers how to take the reading.
Planting day
Plant in the cool of the day, late afternoon or an overcast still day, not a hot windy one. Water in well with diluted seaweed. In hot weather shade the new plants for the first few days: a square of 50 per cent shade cloth on stakes, or a bottomless pot or upturned crate over each seedling, and take it off once they stand up on their own.
Where nights are still cold, a cloche made from a plastic bottle with the bottom cut off, a cold frame, or a sheltered spot against a north-facing wall is the halfway house.
A note for every zone
Brisbane, the Gold Coast and the Sunshine Coast are mostly past this: the soil is warm and hardening off is a matter of days. Sydney, Newcastle, Wollongong and Perth are in the window now, Bunbury and Albany run a couple of weeks behind Perth, and Perth's afternoon sea breeze is the reason to start with morning light only. Adelaide, Melbourne and Geelong harden off through October and plant from the middle of the month as the readings allow. Canberra waits for the last frost, often early November; Hobart's traditional marker is Show Day in late October; and in both the cold frame is the bridge that gets seedlings there.
Grow it: seeds in stock
Four lines that go through this routine every spring.
Tomato Oxheart Pinka big heirloom that repays the deep planting leggy seedlings need.See the seeds
Capsicum Californian Wonderthe classic bell capsicum, potted on once and planted out at the same depth it grew.See the seeds
Chilli Jalapenoslow to start and worth the wait; sow under cover and hold until the soil is warm.See the seeds
Basil Lemonthe last one out of the door, once nights stay mild.See the seeds
A week of half days is a small price for a seedling you have already spent six weeks on. Our lesson on why coriander bolts covers the herbs that would rather be sown direct than moved at all.
Frequently asked questions
My seedlings are ready but the soil is still cold. What do I do?
Pot them on into a bigger pot and keep hardening them off. A tomato potted on will wait a couple of weeks quite happily; a tomato planted into cold soil can sit and sulk for weeks.
What if a frost is forecast the night after I plant?
Cover each plant at dusk with an upturned pot, a bucket or a cloche, and take it off in the morning. One cold night under cover usually does no harm.
