How to Plant Aubergines: Choosing Plants and Soil Temperature

Choose by stem thickness, not height

A tall plant looks impressive and grows badly. What you want is a short, stocky plant with a thick stem, which is what you get from a plant grown in good light rather than pushed in warmth.

1. Stem thickness The stem at soil level should be as thick as a pencil or thicker. The lower the seed leaves sit and the stockier the plant looks, the better the conditions it was grown in.
2. Leaf color and thickness Green but not too dark, with thick leaves held out flat. Leave anything with yellowing lower leaves, fine white speckling underneath, or scratched feeding marks.
3. The rootball A few white roots just showing at the drainage holes is right. A rootball wound solid with brown roots takes a long time to put out new ones after planting.

Why grafted plants are worth it

Aubergines are prone to soil-borne wilts, and once one gets into a plant there is no cure. A plant grafted onto a resistant rootstock avoids most of that, which matters a great deal if you have limited ground and cannot rotate properly.

They cost more, but on any plot that has carried aubergines, tomatoes or peppers in the last few years the difference in reliability is large.

The graft union must stay above the soil. Buried, the top puts out its own roots and you lose all the resistance you paid for.

Plant by soil temperature, not by date

Aubergine is the most heat demanding of the common fruiting vegetables. Planted into cold soil it does not simply grow slowly, it sits and sulks and never builds a strong plant. Wait until night temperatures are reliably above about 59F (15C).

A collar of plastic around the plant is enough. It matters less for warming the soil than for stopping the leaves being damaged by late frost and wind.

Soil preparation and spacing

Aubergines root deeply and crop for a long season, so the preparation has to go deeper than for a quick crop. Aim for a pH of 6.0 to 6.5.

1. Two weeks before Lime if the soil is acid and dig deeply. On acid soil the roots do not extend, and everything after that is limited by it.
2. One week before Work in well-rotted compost and a balanced fertilizer and build a bed two feet (60 cm) wide and four to six inches (10 to 15 cm) high.
3. On the day Space plants 20 to 24 inches (50 to 60 cm) apart. Aubergines spread their branches widely, and crowded plants shade their own centers, so the fruit colors poorly and marks easily.

How to plant

Everything here is about getting the roots moving quickly. A plant that establishes in a few days rather than a couple of weeks is a different plant by midsummer.

1. Water the hole first Dig the hole, pour water in and let it drain before setting the plant. That wets the soil around the rootball evenly, and the plant establishes several days sooner than if you water over the top.
2. Plant shallow Set the top of the rootball level with the bed or very slightly proud. Planting deep buries the graft union and puts the rootball into colder soil.
3. Add a temporary cane Push a two foot cane in at an angle a little away from the plant and tie the stem loosely in a figure of eight. Wind rocking the plant breaks roots and it has to start again.
4. Cover the soil Black plastic or straw around the plant holds warmth, stops soil splashing disease onto the leaves and slows drying, all at once.

The first fortnight

Leaf color is the quickest guide to feeding. Leaves curling inwards and going very dark means too much, and lower leaves fading to pale green means too little.

1. Week one Water thoroughly at the base every two or three days. Wilting at midday is fine as long as it is firm again by morning. Do not feed.
2. Week two A new leaf opening means it has taken. Check the tie and move it up as the plant grows, and start stretching the interval between waterings.
3. The first flower You can leave the first flower bud, but pick the fruit off while it is still thumb sized and let the plant build itself instead.

If it does not get away

Most problems in the first month come down to cold soil, water or feeding, and treating the wrong one makes it worse.

The cut-off for replanting is about six weeks after your normal planting date. Later than that the plant never builds before the heat arrives.