Growing Concerns 36: Choosing better tomatoes, using peat, beating slugs

Early Spring!


Plan now to change that tomato's yellow shoulder

Also: peat, and slugs

For the past few years our tomatoes have been ripe on the bottom but the upper part stays yellow and hard; this part is white and hard inside, too. They get a lot of sun and are planted on the south side of the garage, which is covered with white aluminum. Could heat reflecting off the aluminum cause this? - L -

A tomato condition called yellow shoulder fits your description. "Blotchy ripening" is a similar problem but doesn't restrict itself to the upper part around the stem. These aren't diseases but cosmetic problems: normal red pigment just fails to develop in those tissues.

Some experts say yellow shoulder is genetic, so some tomato varieties are prone to it. Others say it's due to adverse growing conditions. Whichever one, you can handle it.

Switch varieties to one that you've seen that can turn completely red. That covers the genetic angle.

Several growing conditions can contribute to yellow shoulder. Low light levels can cause it, but probably not in your sunny bed. Too much light on the fruit itself or overly high temperatures during the ripening period may well be the culprit in your case. More yellow shoulder seems to occur on tomatoes at the top of the vine, and on plants that have lost top leaves to diseases and insects, because fruit there doesn't get filtered shade from foliage. Try moving your tomatoes away from the heat. This will also help you stay ahead of defoliating insects and diseases, by getting the plants away from pest populations that may have built up

Low potassium levels can lead to yellow shoulder, too. Use a complete fertilizer with adequate potassium, such as 10-10-10


Last fall, I asked my husband to get some peat moss for my garden. He bought a huge bale of Canadian peat. How can I use it all?

Canadian peat is partially decomposed plants, harvested from bogs. Although its production has become controversial - Should we be draining and emptying bogs of their peat? - there's no doubt that it's good for a garden. It greatly improves soil's water- and nutrient holding capacity, breaks up heavy soil, and reduces alkalinity.

If you grow plants from seed, use a fine layer of peat to cover the soil once seeds sprout. This discourages "damping off" fungus that can wipe out a whole flat of seedlings overnight.

Outdoors, spread it 2-3 inches deep on the soil and dig or till it in. The particles act like sponges, attracting many times their weight in water and nutrients, holding them until roots can get there.

Like a dry sponge, though, dry peat might repel water at first and need a bit of coaxing to start absorbing. I've dug up peat chunks that were still dry after a year in the soil. Dry peat is of no use to plant roots, so I get it wet before digging it in. Put it into a bucket, add water and knead. Or punch a hole in the plastic bale, insert the hose end, trickle in water and let it sit 'till it's soggy.

You can also use it as mulch, spreading it on top, two to three inches deep. It insulates and keeps the surface moist, smothers weed seeds, and gradually mixes in to improve the soil. Again, best to wet it before spreading it, or irrigation water may bead up and run off.

(Some additional thoughts developing now about the use of peat, here  on our Forum)


My back yard is shaded, so I planted hostas. The slugs are proving to be my nemesis. I have a dog, lots of squirrels and birds. I am fearful of putting out anything that would hurt them. Can you offer any suggestions?

Where slug populations have boomed, it's fairly simple to de-fuse the situation if you act early, in April and May.

In April, rake out all mulch and debris from your hosta beds. With it comes lots of slugs and slug eggs. Compost this stuff, or give it to a yard waste collector to compost. The heat of a regularly-turned compost pile kills slugs and their eggs.


Originally published 3/26/94