Garden Detective

Garden detective: Yellow eggplant is a head-scratcher

Eggplants should be picked before they are over-ripe.
Eggplants should be picked before they are over-ripe. Bigstock

I have an eggplant in a pot on my patio that forms a nice-looking purple fruit, but then as it matures, it turns yellow. I think I’m watering and feeding appropriately, so I’m not sure what’s going on.

Joanne Pierce, Sacramento

Because the plant and fruit look otherwise normal and healthy, there are three likely possibilities:

▪ Variety. Some eggplants – especially lighter colored varieties – develop yellow fruit or yellow streaks as a natural trait. What variety did you grow? Had you grown this variety before, and did that fruit turn yellow?

▪ The fruit is over-ripe. Several varieties of eggplant, especially those lighter ones, will turn yellow when the seeds are fully mature. Pick the fruit a little early while it’s still purple.

▪ Sunburn. Like peppers, eggplant are prone to sunburn, especially if they’re growing in a south- or west-facing bed. Those yellow patches may actually be sun damage.

Generally, sunburn appears as white or tan blemishes on the fruit, but those sunspots can turn yellow. Sunburn happens most often when the plant has lost leaves and the young fruit becomes exposed to too much ultraviolet light.

If the plants get blasted by late-afternoon sun, erect some shade cloth or other temporary shade protection to keep the fruit from scorching.

The yellow spots usually can be cut off. The important thing is the flesh beneath the skin and how it tastes.

Other possibilities could be pest-related, but you likely would have seen other signs than just yellow fruit.

According to the UC Davis experts, pepper weevils can cause the fruit to turn yellow, but the eggplant will usually have holes or become misshapen in addition to developing odd-colored blotches. Weevil larvae are white, legless and found inside the fruit. The adults are dark little beetles about an 1/8-inch long. To help rid your garden of these weevils, destroy (don’t compost) the plants after harvest.

Spotted wilt virus, spread by thrips, may cause yellow spots and rings to form on the eggplant or an overall yellowing like chlorosis. But the fruit also looks oddly shaped. This virus can be controlled by removing nearby weeds, which serve as a host to the thrips.

So, most likely, with your patio plant, it comes down to harvesting the eggplant before it turns yellow.

How do you tell when an eggplant is ready to pick? The experts at the UC Davis Vegetable Research and Information Center recommend this method:

Pick eggplant when the fruit are about 4 to 6 inches in diameter. (The exception is Japanese and dwarf eggplant, which will have a smaller diameter.) Test for maturity by pressing with the skin with your thumb. If the flesh springs back, the fruit is green; if it does not and an indentation remains, the fruit is fully mature.

Harvest when the fruit is about halfway between these two stages; there still will be a little spring in the flesh. Mature fruit should not be left on the plant because they will reduce overall productivity. Don’t pull off the fruit; use a knife or pruning shears to cut it from the plant.


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