2016-07-20 / Gardening Tips

Gardening Tips

Blossom end rot
by Bob Beyfuss

Vegetable gardens are growing at the fastest rate of the season right now as we enter the middle of July. Soils have warmed to well above 70 degrees and as the root system expands, the top growth shoots up exponentially. I cannot really comment on the drought because some of our region received as much as six inches of rain last week while others had an inch or less. I hope your garden was somewhere in the middle, with about three inches!

What causes it and how to prevent it

I have already heard of some cases of “Blossom end rot” (BER) on tomatoes. This is a physiological malady that occurs when the first fruit to ripen develop a black area on the bottom that eventually rots. To some gardeners, it looks like a fungal disease that is attacking the tomato fruit. If you do research on this, you will learn that it is technically caused by a calcium deficiency. That may be “technically” true but the real cause is that the root system of the plant is unable to supply enough water to supply the whole plant with dissolved calcium. Calcium is not selectively absorbed by plant roots, as are other nutrients such as Nitrogen or Phosphorus or Potassium. It is present in the soil and is carried passively into the whole plant as the plant absorbs water, but when the root system is not fully developed or functioning properly, the deficiency occurs. Anything that interferes with proper root development can cause blossom end rot. It most common ly occurs when oversized transplants are set out in the garden. If the transplant already has flowers or fruit on it, these first fruit are most likely affected. Soil that is still cool in late spring/early summer, or soil that is so wet as to inhibit root growth also contribute to the malady. I do not set out my tomato transplants until the soil is at least 70 degrees. Even hoeing too close to the plant can sever shallow roots and cause BER. Trying to grow big tomatoes in small pots or containers can also be an issue. There are some varieties of tomatoes that can be grown in large pots, but standard sized tomatoes, such as my favorite “Big Beef” will not do well in anything smaller than a five gallon or larger container.

Some fact sheets, or other gardening advice is to add lime to the soil to increase the pH and provide more calcium. If you soil pH is above 6.0, as most backyard garden soils are, this is not at all necessary. There is plenty of calcium available when pH is 6 or higher. Spraying the plants with calcium nitrate or some other supplement al calcium source is also not necessary.

How long must I wait for that first tomato?

The good news is that BER usually cures itself once the roots develop and can supply enough water. The bad news is that it is the most eagerly awaited, very first ripe tomatoes that end up on the compost pile! Some of us have waited almost a year to enjoy the flavor and texture of a homegrown tomato, picked right off the plant! (I almost wrote “right off the vine”, but tomato plants are certainly not vines!) It is indeed disappointing to have to wait even longer!

If this happens to you this season, make a note to change your cultural practices next year to avoid a repeat. Some of us repeat the same gardening mistakes year and after year! Most years it is the local raccoons that tell me my sweet corn should have been protected by hooking up the electric fence earlier! This year, a woodchuck got in and ate my peas, spinach and cauliflower before I hooked it up. I don’t always follow my own advice!

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