Tomatoes are the most commonly grown plant in the home garden, so it is no surprise that I get so many questions about them.

One of the most common questions is about blossom end rot. This is a brownish, leathery spot on the blossom end of tomatoes. It can appear on either green or ripe fruit. Blossom end rot occurs because the cell walls at the end of the tomato are collapsing due to a lack of calcium. But before you jump to the conclusion that this means the soil is lacking in calcium, let's dig a little deeper.

It usually means that the plant cannot take up an adequate amount calcium from the soil quickly enough. That is often because the roots have not developed sufficiently. And that is usually because the tomatoes were set out in the garden before the soil (not air) temperature had reached a minimum of 65 degrees, which is what this tropical plant likes. Get a soil thermometer if you don't have one.

Two other conditions may contribute to blossom end rot. One is the drought-and-drown method of watering, which means letting the plant get too dry, and then flooding it with water. Tomatoes need deep, even watering. The other factor is that some varieties of tomatoes are more susceptible to blossom end rot. Much as I love them, I find this is true of Romas, for example.

Sunscald, or sunburn, is another condition people ask about. This is a light yellow or white, rather hard patch on the tomato caused by the sun literally burning the fruit. First, keep in mind that tomatoes do not need to have the sun shining directly on them in order to ripen; they just need heat. In this climate, I discourage the practice of pruning tomato plants for that reason, as the leaves act as a parasol for the fruit. If you have already pruned leaves from your tomato, you might want to put some row cover (Remay) or light shade cloth over the plant.

Irregularities such as grooves or tan, callus-like lines are called catfacing, and are caused by incomplete pollinization. Not much we can do about that.

Happily, none of the nuisances mentioned above make the tomato unsafe to eat, or even affect its flavor. They are cosmetic problems, so just trim out the unsightly part, and enjoy the rest of the tomato.

One other question we hear frequently, especially this year, is, “Why do my tomatoes stop setting fruit, or slow down the ripening process, when the temperature goes over 90 degrees or so?” Let's look at that from Mother Nature's point of view.

Although we'd like to think that tomatoes exist for our pleasure, the fact is that they are intent on reproducing themselves to keep the family line going. So, when temperatures are too hot, as they have been lately, the tomato shuts down a bit to wait for better conditions for the seeds it's producing.

You can cheat on this one a bit by bringing almost-ripe tomatoes into the house and letting them finish the ripening process there. However, never put tomatoes in the refrigerator at any stage — it quickly ruins the flavor.

Coming up: Master Gardener Michele Pryse will discuss how to save seeds from your garden from 7 to 9 p.m. on Thursday, Aug. 21, at the Southern Oregon Research and Extension Center, 569 Hanley Road in Central Point. The cost is $10. Call 541-776-7371 to sign up.

Carol Oneal is a past president of the OSU Jackson County Master Gardeners Association. Email her at