3 Ways to Solve Aubergine Pollination Problems

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Aubergine fruits

Six years ago, after I wrote 5 Tips for Growing Excellent Aubergines, questions started coming in from gardeners with healthy, well-tended aubergines (also known as eggplant) that refused to bear fruit.

“I’m getting flowers but no fruit, plenty of bees from my own hives. Have fertilized, used composted soil and plenty of water, and they’re in a good, sunny spot,” wrote Bev, one of many frustrated folks who reported aubergine pollination problems.

What could be wrong?

Aubergines flowers
Aubergine blossoms with long styles (left) are more likely to set fruit than those with shorter styles (right)

1. Hand-Pollinate Aubergines

It’s normal for the first few aubergine blossoms to drop, but after that you want to see some cute little fruits forming. It could be a lack of insects visiting the flowers, because even though eggplant flowers are self-fertile, the vibrational buzzing of bees helps move pollen grains about inside the flowers. Should you want to hand-pollinate aubergine blossoms, touch the stem behind the flower with a vibrating toothbrush several times during the morning hours. Repeat the next day.

While you’re checking your aubergine blossoms up close, see if the stigma, at the end of the style, protrudes from the centre of the flower, as shown in the left photo above. Aubergine flowers with long styles like this one are usually ripe for pollination, but some varieties have shorter styles that barely show, as seen in the photo on the right. These are less fertile flowers. To further complicate things, aubergine varieties with normal styles may get moody about reproduction and switch to short ones. This is one of the ways aubergines respond to stress, especially drought.

The plants are not being grumpy, but rather responding like resilient perennials, which is what they are. Though we grow aubergines as annuals, in semitropical and tropical climates they are short-lived perennials. When the weather gets too hot, dry, dim, or cold, they hunker down and wait for better days.

Row of young aubergines
After a healthy start under row covers, these aubergines are ready to have their lower side branches pruned to support strong growth of the vertical leaders

2. Pruning Aubergines to Improve Pollination

Okay, so aubergines want to be a bushy tropical perennial, which may not work out well in a summer garden. Left to their own devices, aubergine seedlings will produce one or two upright primary stems, and then start bulking up with side branches that emerge near the base of the plant. When these are pruned away, the plants recalibrate by channelling energy back to the upright stems and new flower clusters. When their plans to grow into big bushes are thwarted, the plants get more serious about producing fruit. Give pruned plants sturdy stakes or a cage, and they are ready to go.

Consider this report from a reader on pruning aubergines to improve pollination. “I had flowers falling off for almost two months. I plucked out all the flowers and trimmed off the leaves at the bottom levels of the plant. After doing that, the plants finally produced flowers with strong stems that developed into eggplants.” Success at last!

Aubergines have become a popular crop for vegetable farmers to grow in polytunnels, and quite a bit of research has gone into best pruning practices to maximise productivity. Many polytunnel growers prune plants to two leaders, use a vertical trellis, and pinch out lower side branches to help maintain the leaders’ dominance.

Different shapes and sizes of aubergine
Aubergine varieties that produce small to medium fruits are more likely to set fruit under adverse conditions

3. Give Aubergines More Morning Sun

Aubergines grow best in full sun, which means 6 hours or more of direct daily sun exposure. Plants that don’t get enough sun often grow into beautiful specimens, lush with leaves, but with hardly a blossom or fruit. If plants must run short of sun, make sure it’s not morning sun, which has special benefits for aubergines with pollination problems. Morning sun gets the plants up and running early in the day, with new blossoms and fresh pollen for the bees, who are busiest from midmorning until noon. Moving container-grown aubergines to a place that gets full morning sun may solve your pollination problems.

Too much fertiliser can be a factor in aubergine pollination problems, but because aubergines require frequent watering, excess nitrogen is likely to be washed away. In terms of soil fertility, prepare planting holes for aubergines just as you would for tomatoes and peppers, by mixing in compost and a balanced organic fertiliser. After that, a deep drench with a high nitrogen liquid fertiliser at 4 and 8 weeks after planting can help keep plants in a flowering mood.

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