Leggy seedlings and the lamp I should have bought in January
The problem with starting chillies in January is that the seedlings arrive on the windowsill in the darkest weeks of the year. This year the first batch came out of the boiler cupboard on the 2nd of February, onto a kitchen windowsill that faces north-west and gets no direct sun until April. By the 20th they were 9 centimetres tall with a single pair of seed leaves and a stem the thickness of a cotton thread, leaning towards the glass at forty-five degrees. That is a leggy seedling, and once it has stretched it does not shrink back.
The lamp arrived on the 24th: a small full-spectrum grow lamp with a clamp, the kind that fits on a shelf edge. I clamped it to the curtain rail so that it hung about 20 centimetres above the pots, and plugged it into a timer running from six in the morning to eight at night. The light is a cold pinkish white that makes the kitchen look like a fish tank in the evenings, which the rest of the household has opinions about.
The effect on the second batch, which came out of the cupboard on the 1st of March and went straight under the lamp, was clear. At three weeks those seedlings were 5 centimetres tall with two pairs of true leaves and stems I could not easily bend. Comparable seedlings from the first batch at three weeks had been 9 to 10 centimetres with no true leaves at all.
The first batch I tried to rescue. Repotting them deeper, burying 3 centimetres of the stretched stem, helped a little, since chillies will root from buried stem and it stops the wobble. Under the lamp they stopped stretching and put on true leaves. But in late March, when I set the two batches side by side, the early ones were still thin-stemmed and top-heavy, and I think they will always be a step behind. I will keep the four best and give the rest away.
The obvious lesson is to have the lamp before the seeds, and to count the lamp as part of the cost of starting early. The less obvious one is that a south-facing windowsill would have solved this for nothing, and I do not have one. Fourteen hours of lamp at 20 centimetres is the compromise this house allows.