Five Avoidable Tomato Problems
Tomatoes enjoy a highly pampered status in many
vegetable gardens, and rightly so. Fresh juicy
tomatoes are a hallmark of summer and a key
ingredient in many summer dishes. So when tomato
fruits become misshapen or damaged, it can be
cause for alarm. It's easy to blame pests or
diseases, but the weather or even your gardening
practices may be the actual cause.
Here are some common tomato fruit problems not
caused by insects or disease. Tomato experts call
the stresses physiological problems, meaning the
cause has to do with the functioning of the plant
itself, not with any outside agent. By taking the
recommended steps now, you can help ensure that the
next cluster of tomatoes on your plants is picture
perfect.
1. Blossom-End Rot: Brown-black sunken areas appear
on the blossom end of green or ripening fruit.
Causes:
Insufficient calcium levels in the developing fruit
cause the cells in the blossom end to break down.
Though insufficient levels of calcium in the soil
may be the cause, it is more likely fluctuating
moisture levels. Water transports calcium through
the plant. With insufficient water, calcium doesn't
move quickly enough to the fruits. As little as 30
minutes of water deficiency at any time can cause
blossom-end rot. This is why it is important to
apply a mulch, which helps retain water in the
soil.
The following factors contribute to blossom end rot
availability in the developing fruit:
excess nitrogen fertilization, high soil salinity,
waterlogged soils, root damage during cultivation,
and soil pH that's too low or too high.
What to do:
Pick and destroy rotten fruits; keep the soil pH
around 6.5; reduce nitrogen fertilization; and
apply a complete fertilizer, such as Burpee's Big
Boy Tomato Food.
Also, mulch early in the season with a 4- to 6-
inch layer of hay or straw. Apply at least 1 1/2
inches of water a week.
2. Blotchy Ripening (graywall):
Light green or clear blotches on green fruit that
gradually turn yellow, and uneven ripening. Often,
the tomato is rotten inside.
Causes:
Graywall is most often caused by shade and cool
temperatures followed by bright, sunny weather.
Excessive foliage growth also causes it, so the
most vigorous indeterminate tomato varieties are
the most susceptible. It occurs more often in
plants growing in soggy soils, and diseases like
tobacco mosaic virus may indirectly cause this
condition.
What to do:
Grow determinate bush varieties that allow sunlight
through the leaf canopy. Decrease nitrogen
fertilizer, and increase potassium. Stake or cage
plants to allow sufficient light to reach the fruit.
Burpee's Tomato Tower allows you to easily stake
plants without tying, and Burpee's Tomato Cages can
be stacked two high for extra tall plants. (See the
Tomato Tower) ,and see the (Tomato Cage)
3. Fruit Cracks:
When ripening, fruits crack around the stem end
and along the sides, and the fruit rots. Cracks
may be radial or concentric.
Causes:
Abruptly alternating wet and dry periods cause
cracking. When the plant takes up deep drinks of
moisture after a dry spell, the fruit cells expand
too fast and burst, and the skin cracks. (Heavy
dew worsens cracking because the fruit can take
water in through the skin.) Too much nitrogen in
the soil also contributes to the problem. Green
fruits usually don't crack because they're harder
and can't expand as fast, and their skin cells are
stronger.
What to do:
Keep the soil evenly moist, especially during
ripening, with a 4- to 6-inch mulch of hay or
straw. Don't overfertilize.
4. Green (or yellow) Shoulders:
The "shoulders" on the tomato's stem end stay
green (or yellow) and hard as the rest of the
fruit ripens.
Cause:
Normally chlorophyll breaks down as the fruit
ripens. However, in some varieties, during
periods of high temperatures and direct sun
exposure, the chlorophyll does not break down,
or does so too slowly.
What to do:
This problem is most common in heirloom varieties
that happen to lack the gene for uniform ripening.
Most modern hybrids have this gene and rarely
develop green shoulders. However, if you want to
grow the older, susceptible varieties, minimize
green shoulders by maintaining good foliage cover
and picking the tomatoes when they're entirely
green to ripen indoors, away from exposure to
direct sun.
5. Sunscald:
Fruit has lighter-colored leathery patches, and it
usually rots.
Cause:
This discoloration is like a sunburn. Fruits
exposed either suddenly or continually to hot sun
develop sunscald, which is most likely to occur on
varieties that don't produce enough leaves.
What to do:
Avoid pruning leaves or stems while the fruit is
ripening, and consider shading the fruit. A small
section of shadecloth or row cover would suffice.
Finally, try to reduce the severity of leaf
diseases such as early and late blight, common
fungal diseases. If you live where summers are
sunny and hot, grow indeterminate varieties that
produce a thick cover of shading leaves.
Q. What are the advantages and disadvantages
of pruning tomato plants?
A. Some indeterminate plants grow so large and
heavy that it is impractical to let them reach
full size, or they may try to set more tomatoes
than they can support, or more than can mature
by the end of the season. Pruning can produce a
more manageable plant and crop, increase air
circulation within the plant to reduce disease
problems, and speed ripening by allowing more
sunlight to the interior of the vine. On the
other hand, excessive pruning can reduce the
amount of energy the plant can produce (because
leaves manufacture food for the plant), and thus
reduce yield. Pruning also exposes the fruit to
excessive sun and can contribute to sunscald.
