summer, the bottom of many of my tomatoes had black, rotten spots.
Although the rest of the fruit was usable, these spots were not very
appetizing. What can I do to avoid the problem this year?
you are describing is blossom end rot. It appears as dark brown or
black leathery areas on the blossom end of maturing tomatoes.
Despite the name, it is a nutrient deficiency rather than a disease.
Blossom end rot develops due to one or more of the following
factors: calcium deficiency, drastic fluctuations in soil moisture, overfertilization,
or root damage caused by cultivation.
be present in your soil mix in sufficient quantity, but is
unavailable to the plant due to lack of soil moisture, or because
the fine feeder roots have been severed by hoeing near tomato
To avoid a
recurrence of the problem, have your soil tested to make
sure that calcium levels are adequate. Soil test kits are available
from your local Penn State Extension office for a nominal fee. In
Allegheny County, consumer soil test kits cost $12 each, and come
with detailed instructions for taking a good soil sample and
information to help you understand your soil test results. Customers
ordering multiple kits at one time pay $9 each for the additional
kits. Send a check made payable to Penn State Extension and mail it
to: 400 North Lexington Street, Pittsburgh, PA 15208.
Write Attn. Soil Test Kit in the lower left corner of the envelope.
You may also pick them up in person, Monday through Friday from 8:30
a.m. to 4:30 p.m. Take the sample according to the directions in the
kit, and send it to the soil analysis laboratory in University Park,
PA. Follow their recommendations for limestone and fertilizer
Soil Test Results
MORE THINGS YOU
Maintain even soil moisture by watering regularly and mulching your
tomato plants. You may use an organic mulch such as straw, or an
inorganic mulch such as black or red plastic. Mulching helps
maintain soil moisture, moderate soil temperature, and it also keeps
weeds under control. Be very careful about cultivating near tomato
plants as you can sever fine feeder roots and make the plant think
that it is under moisture stress - which will cause blossom end rot.
Although tomatoes are classified as heavy feeders - which means they
require additional fertilizer applications through the growing
season - do not apply more fertilizer than your soil test results
suggest. Too much nitrogen results in a lot of vegetative growth
and little or no fruit, and it also can cause blossom end rot
because excessive nitrogen blocks the plant from taking up calcium.
Blossom end rot can be a big problem for gardeners who grow tomato
plants in pots. If you ever allow container-grown plants to dry out
to the point of wilting after they have set fruit - even one time -
all of the fruit present when wilting occurred will have blossom end
rot. (As long as it does not dry out again, fruit that forms after
will be undamaged). To avoid this, be sure to plant tomato plants in
large containers - at least equivalent to a five-gallon bucket.
Remember to water tomato plants thoroughly every day. The leaves of
larger plants will shed rainwater outside the pots, so you have to
water even when it rains. You can use a fine-textured mulch over the
soil surface to help conserve water. Some gardeners use sphagnum
moss for decoration as well as conserving moisture.