A question was posed to me the other day about green shoulders—the unripe area around the stem of some tomatoes. You can see a faint example in the second pic of one of my earlier posts. The question was whether that’s really an unripe area or whether it’s sunburn.
In my experience, it’s definitely unripeness. Some varieties of heirloom tomatoes are predisposed to having green shoulders to the point that the trait is a part of seed sellers’ descriptions. However, my Web digging found several reliable sources that say this genetic trait is triggered by high temperatures and direct sun exposure. So that may be why some people think of green shoulders as sunburn.
Charles Nardozzi of the National Gardening Association writes about green shoulders: “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.”
Now there is another condition, called sunscald, that is much more like what happens to human skin when we get too much sun. Nardozzi on sunscald: “What it looks like: The fruit has lighter-colored leathery patches, and fruit usually rots. … 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.” Vegetable expert Howard Wener writes, “The leaves protect the fruit from the sun and help create a favourable microclimate.”
Leaves: Love ’em and leave ’em.