Dig In: Garden checklist for week of July 15

Watch tomatoes for potential wilt. (Photos: Kathy Morrison)
Watch for wilting tomatoes, but don’t automatically turn on the hose

By Debbie Arrington

In July heat, it’s hard not to wilt, especially on a triple-digit afternoon.

When it comes to tomatoes, not all wilts are the same. Some are due to water (not enough or too much), others are signs of fungal disease.

Afternoon wilt is normal in many tomato varieties. It’s a reaction to water loss in the leaves. If the plant loses moisture faster than it can pull it up from its roots, the foliage becomes limp as cells deflate. Usually as the temperature cools later in the day or overnight, the plant regains its water balance and the leaves return to their normal stance.

If the leaves are still wilted in the morning, then the plant likely needs a drink. Test the soil to see if it’s dry. Poke a screwdriver into the ground; if it can’t penetrate more than 2 inches, insufficient water is definitely the problem.

How much water? A mature tomato plant needs 5 to 7 gallons a week during Sacramento summers.  That can be a gallon a day on drip irrigation systems or deeper watering two or three times a week.

Too much as well as too little water can cause tomatoes to wilt and drop leaves.  Plants need air pockets in the soil to let their roots “breathe” and process needed moisture and nutrients. If the soil becomes oversaturated, the plant can’t cope. That wilt is a warning sign.

Tomatoes can bounce back from water-related wilt like this,
but other wilts can be trouble.
Tomatoes generally can bounce back quickly from water-related wilt.  However, fungal wilt is always deadly.

Tomatoes suffer from two major kinds:  Verticillium (http://ipm.ucanr.edu/PMG/r783100911.html) and Fusarium (http://ipm.ucanr.edu/PMG/r783101011.html). Both fungal wilts clog the plant’s vascular system. The vines can’t bounce back from wilting because they can’t pull up more water from their roots. Leaves soon turn brown and quickly the whole plant dies.

Many hybrid tomato varieties are resistant to fungal wilts, but heirlooms are still susceptible. These fungal diseases can lurk in the soil and attack new plants, too.

According to the UC Cooperative Extension Master Gardeners, tomatoes infected with fungal wilts should be removed and discarded (not composted).  No tomatoes or other nightshade family crops (such as peppers or eggplants) should be planted in that same spot for at least two seasons.

Wilt also may be caused by unfriendly neighbors in the tomato bed.  Sunflowers excrete a substance into the soil to inhibit competition from other plants.  Tomatoes don’t like it and may wilt more often if planted in the same bed as sunflowers.

Besides keeping an eye on wilting tomatoes, other garden tasks for mid-July:

* Harvest tomatoes, squash, peppers and eggplant. Prompt picking will help keep plants producing.

* Pinch off blooms from basil so the plant will grow more leaves.

* Feed vegetable plants bone meal or other fertilizers high in phosphate to stimulate more blooms and fruit formation.

* From seed, plant corn, beans, pumpkins, radishes, winter squash and sunflowers.

* Remove spent flowers from roses, daylilies, agapanthus and other summer bloomers as they finish flowering.

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