Six seasons of trying to overwinter chili plants in the cool pockets of Sydney’s west has taught me more about plant resilience than I expected. Some years I lose half the collection. This year, with a cooler-than-average autumn and a few proper cold snaps in May, I lost two plants out of forty-three. The technique adjustments that produced that result are worth writing down.

The pruning timing

I used to prune for overwintering when I noticed the leaves yellowing in mid-autumn. That is too late. The plant is already stressed by the time the leaves yellow, and the pruning shock combined with the temperature shock takes plants out.

This year I pruned hard in early April, before the first cold nights. The plants had time to put a small flush of leaves on before the real cold arrived, which gave them the photosynthetic capacity to ride out the winter. The plants pruned in early April uniformly outperformed plants I have pruned later in previous years.

The moisture management

Cool-climate overwintering kills more chili plants through root rot than through frost. The plant slows transpiration in the cold. The soil holds moisture much longer than it does in summer. If you water on the same schedule as summer, you will rot the roots.

I shifted to checking soil moisture by weight rather than by appearance. Lift the pot. If it feels heavy, do not water. The plants that died this year were the two I forgot to weight-check and watered out of habit.

The wind protection

Sydney’s cool pockets get more wind than people realise. The wind chill on a 5-degree night with 15-kilometre wind takes plants down that would survive a calm 2-degree night.

I moved the pots into a sheltered corner of the yard in mid-April. Not a greenhouse — just behind a fence with overhead canopy. The wind reduction made the difference for several of the more sensitive varieties.

The variety differences

The differences between varieties are large. The Capsicum chinense varieties — habaneros, Scotch bonnets, ghost peppers — are the most cold-sensitive. They need the most protection and lose the most leaves.

The Capsicum annuum varieties — jalapenos, cayenne, serranos — are tougher and can take more cold with less protection.

The Capsicum baccatum varieties — aji amarillo and similar — sit in between but are surprisingly resilient when established.

The pubescens varieties — rocoto — actually prefer cool weather and are essentially indestructible at Sydney winter temperatures.

If you are starting an overwintering operation and you are in a cool climate, lean toward annuums and pubescens. The chinenses are a project.

The result this year

Forty-one plants survived. The largest, an aji limon now in its fourth season, came through with barely a leaf lost. The two plants I lost were both younger chinenses in their first overwintering. The lesson there is that first-year chinenses should probably come inside in cool climates.

Spring is going to be productive. The plants are already starting to flush new growth as the days lengthen. The aji limon is going to produce a serious harvest this season if the summer cooperates.