Diagnose your tomato troubles

High Desert tomato gardeners need vigilance

By Liz Douville / For The Bulletin


Published Aug 19, 2014 at 12:09AM / Updated Aug 19, 2014 at 12:58AM

We need to be honest with ourselves. We all love a red, ripe, juicy homegrown tomato, but there are times when we look at a failing plant and vow that next year we’ll shop farmers markets.

Many of the problems our tomato plants encounter are avoidable. We just need to know what to do once we notice a plant going awry.

Tomato splitting is a common issue resulting from our generosity with the sprinkler. The plant takes up a large amount of water, causing the fruit to swell with moisture until the skin cannot stretch any more. As the high moisture level wanes, the plant will stop taking in so much water, and the fruit will stop splitting.

Overwatering can also cause tomatoes to become tasteless and watery in texture. When a plant starts fruiting, it may start looking a little yellow and tired. That’s when we usually do the “oh dear, oh my” and rush out with water to perk it up. When your plants start looking haggard late in the season, leave them alone. That is how they are supposed to look as all the energy is going into ripening that last flush of fruit. They still need to be watered, but not every day, and they don’t need fertilizer to perk them up.

Every gardener will eventually face the ugly sight of the effects of tomato diseases: curling brown or yellow leaves, black or gray spots or other blemishes that reduce the plant to losing its leaves and reducing yields.

The most common diseases affect the leaves and are referred to as foliar diseases. According to “What’s Wrong with My Vegetable Garden,” 80 percent of the time the problem is a fungus infection.

Changing growing conditions and your practices are the most effective and least toxic solutions. Although the leaves look terrible, the developing fruit generally isn’t affected.

I am having issues with three tomato plants that are in containers in my greenhouse. With the hot spells we have had, I haven’t been able to keep the greenhouse under 95 degrees during most of the day. The fan just isn’t large enough to move the amount of air needed to reduce the temperature. In addition to the temperatures, I probably overwatered, thereby creating the perfect growing conditions for a fungal soil disease.

Many disease agents can remain in the soil for several years, so the options for next year are to dump the soil and sanitize the containers to replant with tomatoes or to rotate to an entirely different planting. I would have to plant something not in the solanum family, which includes eggplant, peppers and potatoes. To sanitize containers, dip them in a solution of 1 part bleach to 10 parts water.

The good news is that the 25-plus tomatoes I planted in raised boxes in the open garden are healthy-looking, with no signs of fungal problems: the difference being good air circulation, less watering and soil that was amended this year.

When checking your plants, remove any damaged, sickly-looking leaves and dispose of them in the garbage — not in your compost pile.

Tomatoes picked a few days before being fully ripe and allowed to sit on the kitchen counter a day or two are usually more flavorful than really ripe tomatoes picked from the vine when soft. Never store tomatoes in the refrigerator, as the cold will reduce sweetness and cause the texture to become mushy. This would not apply to tomatoes that have already been cut or are leftovers. They should be covered and refrigerated.

Dedicated tomato growers will go to any length to bring their crop to the table. I remember reading years ago that Jeff Lowenfels, an Anchorage, Alaska, garden columnist, plumbed a hot water faucet to his garden, and by adding a mixing valve, he achieved the perfect temperature for watering his tomato plants. The system maintained a more stable soil temperature, which promoted rapid plant growth. That was years before the fabric row cover came into existence or the idea of using raised garden beds.

— Reporter: douville@bendbroadband.com