Growing Chilli Pepper Seedlings: Heat, Light and Potting up

Germination is a temperature problem, not a patience problem

Chilli seed wants the compost held at 80 to 85F (27 to 29C) to come up quickly and evenly. At 70F (21C) the same seed takes three weeks instead of one, and a good part of it rots before it emerges. If germination has disappointed you in the past, the compost was almost certainly colder than the room.

The hotter types are slower than the mild ones at any temperature. Give the very hot sorts an extra fortnight in your planning before you decide a batch has failed.

Put the thermometer probe into the compost, not beside the tray. A propagator base can hold the compost ten degrees above the air, and that gap is the whole difference.

Start early enough to matter

Count back from the point where your nights are reliably above 55F (13C), which is when a chilli can go outside. A plant needs eight to ten weeks from sowing to be worth planting, and the hot types want ten to twelve. Sowing late is the most common reason a chilli crop never ripens.

1. Sow into small cells Two seeds per cell in a fine seed-starting mix, covered with a quarter inch (5 mm). Sown too deep in cool compost, the seedling exhausts itself before it reaches the light.
2. Keep it covered until they move A clear lid or a bag holds the humidity so the surface does not crust. Take it off the moment the first seedlings straighten, or they stretch overnight.
3. Thin to one Cut the weaker seedling off at compost level with scissors rather than pulling it, which tears the roots of the one you are keeping.

Light is what decides whether the plant is stocky

Warmth makes a seedling grow and light makes it grow thick. A windowsill in early spring gives too little for too few hours, and the result is a pale plant leaning towards the glass with an inch between each pair of leaves.

As soon as the seedlings are up, drop the temperature to about 70F (21C) by day and 65F (18C) at night and give them the brightest position you have. If you are using a lamp, keep it a few inches above the leaves and run it fourteen to sixteen hours a day.

Brush your hand across the tops once a day, or run a fan on them gently. Plants that are moved thicken their stems, and it takes half a minute.

Potting up and feeding

Chillies resent a check more than most, so move them up before the roots circle rather than after. Each move should be one size, not straight into a large pot where the unused compost stays wet.

1. First move At two true leaves, into a 3 inch (8 cm) pot of ordinary potting mix. Set the seedling slightly deeper than it sat before, up to the seed leaves.
2. Start feeding A fortnight after that move, a half strength balanced liquid feed once a week. Before then the compost has all it needs and feeding only softens the plant.
3. Second move At five or six true leaves, into a 4 to 5 inch (10 to 13 cm) pot. If the weather has turned against you and planting slips, this pot will hold a plant for a month without harm.
4. Pinch the tip, or not Pinching out the growing tip at six leaves gives a bushier plant and slightly later fruit. In a short season leave it alone and let it run.

Hardening off

A chilli raised indoors has soft leaves with almost no wax on them and burns in a single sunny afternoon. Two weeks of gradual exposure is the difference between a plant that keeps growing after planting and one that stands still for a month.

Purple or gray-purple leaves during hardening off are a cold signal, not a feeding problem. The color goes once the plant is in warm ground, so do not respond by feeding it.

Write down what you sowed and when

Note the sowing date, the compost temperature you held, the date the first seedling appeared and the date you planted out. After one season those four numbers tell you exactly how early to start next year and whether your heat source is really doing its job.

Add the position of each plant in the bed as you plant. When one turns out to crop far better than its neighbors, you will want to know which one it was.