Blossom End Rot
Blossom end rot
develops due to one or more of the following factors: calcium
deficiency in the soil, drastic fluctuations in soil moisture,
over-fertilization, or root damage caused by cultivation. Calcium
may be present in your soil in sufficient quantity, but is
unavailable to the plant due to lack of or excessive soil moisture,
or because the fine feeder roots have been severed by hoeing near
tomato plants. It is often worse on plants that are carrying a heavy
crop of fruit because they have a higher need for calcium.
Begin with a Soil Test
To start, have
your soil tested to make sure that soil calcium levels are adequate.
Soil test kits are available from your local Penn State Extension
office for a nominal fee. Send a check made payable to Penn
State Extension to Penn State Extension, 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 applications.
soil moisture by watering when there is not sufficient rain and by
mulching your tomato plants. You may use an organic mulch such as
straw, or an inorganic mulch such as black plastic. Mulching helps
maintain soil moisture, moderate soil temperature, and it also keeps
weeds under control.
Be very careful
about cultivating near squash, tomatoes, peppers and eggplants
because you can sever fine feeder roots and make the plant think
that it is under moisture stress - which will cause blossom end rot.
It is better to hand weed around these plants since it does not
cause as much disruption of desirable plant roots.
Easy on the N
Zucchini are classified as light
feeders, which means they do not require a high level of nitrogen
fertilizer. 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.
There are calcium
sprays available that can be helpful with tomatoes suffering blossom
end rot, but they may not be as useful for squash and other
How to grow tomatoes