Q: Our tomato fruits have yellow tops. Can you tell me what causes this condition? They are the Goliath variety. — Bill Novacek

A: The disorder is called green shoulder, or yellow shoulder. It's caused by a potassium deficiency in the fruit, causing failure of red pigment to develop in the shoulders, but instead they remain green or yellow. The tomato flesh in those areas is often hard, tough and not full-flavored.

It’s possible the soil has sufficient potassium, but the plant wasn’t able to absorb it, resulting in this disorder. The situation is often weather-related, frequently triggered by hot weather, not just when the fruit is ripening, but also when the fruit is first developing.

Some tomato varieties are more susceptible than others. It's often worse when the shoulders of the fruit are exposed to the sun, heating up that portion of the tomato, which triggers the heat/potassium problem.

There's not much that can be done about spells of hot weather. Adding a well-balanced fertilizer such as 10-10-10 at planting time, and again a month later can help assure that potassium levels are adequate. Soil tests are a wise idea to provide a garden soil nutrient baseline. North Dakota State University and University of Minnesota both provide soil testing of samples submitted.

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Q: We are trying to get rid of dandelions in our lawn. We sprayed them about a week ago with Weed B Gon and they are yellowing. Is it best to remove the dying plants or just mow over them? Would all of the weed killer already be absorbed throughout the roots? —Lana H.

A: It's probably better to leave the dandelions in place and eventually mow over them, after they are well-injured from the product you've applied. Removing the plants too early could leave a taproot in place that hasn’t absorbed enough product yet, increasing the chance of regrowth.

Dandelions are quite susceptible to products containing 2,4-D and the plants disintegrate fairly rapidly, so there’s usually no need to remove the dead plant. If mowing at the recommended height of three inches, the dandelions don’t get scalped off, giving the herbicide further chance to work, and the grass quickly conceals the diminishing plant.

Q: Just a note about your stinging nettle story previously in The Forum. While it's true that nettles can be a real pain when one accidentally brushes up against the plant unknowingly, you really don't have to use gloves to pull them out of the garden! — Richard Pemble, professor emeritus of biological sciences at Minnesota State University Moorhead

A: Thanks, Richard, for your fascinating response to my suggestion of using gloves to pull stinging nettle. Richard continues, “As youngsters we had to pull weeds, including nettles, from our family's large strawberry patch. I remember the little rhyme my grandmother taught us about how nettles could be pulled without gloves. It went like this ... Tender handed stroke the nettle, and it stings you for your pains; grasp it like a man of metal, soft as silk it will remain!

“The explanation is that the stinging hairs of the nettle are like tiny hypodermic needles so if you gently brush against them you get a hypodermic shot of several different itching compounds. But, if you 'grasp it like a man of metal' you crush the hairs so they don't inject the compounds.

"I've shown this over the years to many of my students in my field botany classes and they are amazed it works. I've also shown them if they do get stung a most effective cure for the itch is to crush the leaves of the touch-me-not on the itchy skin and almost immediately the itch is gone! Again, my students were really surprised that this works!”

I’m a firm believer in counting the day lost you don’t learn something new, and today I learned something new. Thanks Richard!

If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at kinzlerd@casscountynd.gov or call 701-241-5707. Questions with broad appeal may be published, so please include your name, city and state for appropriate advice.