What’s wrong
when tomatoes don’t ripen evenly? For example, most of the tomato will turn
red, but the stem end, known as the shoulder, remains green or yellow, and even
whitish. This is a physiological disorder known as yellow shoulder, also known
as green shoulder. The shoulder area may
also be noticeably harder than the rest of the fruit.
Scientists have been working on this problem
for many years. They have finally come
up with three potential causes. 1)
Environmental – the disorder can occur when high temperatures, above 90 F,
remain for a prolonged period, and the fruit receives too much direct sun
exposure. 2) Nutritional – it can be
triggered by insufficient potassium and a soil pH above 6.7. 3)
Varieties – although no specific research has been conducted to conclusively identify
the better varieties, there seem to be certain varieties that are less prone to
the yellow shoulder disorder. The problem is more prevalent in heirloom
varieties because many hybrid tomatoes have been bred to alleviate this
problem.
What to do – first, try some other varieties,
especially the newer hybrids. In addition, you may need to increase the amount
of potassium you are applying and adjust the soil pH. If there is a heat wave, create some partial
shade cover for the plants. Letting the
fruit hang longer on the vine in order for the fruit to color does not help and
can increase the potential for rot.
