Honoring Dr. David Graper

Dr. David Graper is highlighted in Plant Exchange Blog this week for his service to everyday gardeners.


David Graper is a Horticulture professor at South Dakota State University and S. D. State Extension Horticulture Specialist and McCrory Gardens horticulturist. He spent much of his career in service to the people of South Dakota and with students. One of the founding leaders of South Dakota Master Gardeners and often coordinator, Dr. Graper retires at the end of April.

These are his responses to a few gardening questions like those that he has received from around the state for decades. His writing here is typical of the interactions about plants that he shared with gardeners.


Flowering vine for hot area, red clay soil

The previous owners of our house put up a large post and lattice structure on our hot dry hillside — maybe to grow grapes? We don’t know. It’s probably 6′ high and 12′ wide. We refer to it as the giraffe hitching post, because it has a high rail you could tie your giraffe to. If you had one. I can get water to that spot and would like to plant something – maybe a vine with flowers. Red clay soil and gets A LOT of sun. Hillside faces west. Any suggestions welcome!

This sounds like a challenging location to grow plants. The combination of full sun and being a dry site in your dry climate there will be tough on plants. Grapes are a possibility, but you will need to keep them watered or else they will not survive and certainly not fruit. You might consider some other types of vines, like Virginia creeper or Boston ivy which do not have showy flowers but do have good fall color. You could also try something like pole beans or even pickles, cucumbers, a smaller fruiting squash or gourds, providing the lattice is fine enough to allow for the vines to grab onto it or wrap their tendrils around it. I would definitely suggest you apply an organic mulch around the plants once they are planted or up and growing, to help keep the soil cooler and retain more moisture. You may want to try using a soaker hose for irrigation. I would also suggest you keep a close watch for pests, especially spider mites and whiteflies. They like to feed on plants in hot dry locations. If all else fails, you may consider the giraffe.


Lime for my lawn

General recommendations tell us to put lime in our lawn if I have a dog. I live in the Black Hills, on a mountain of limestone. Should I lime my yard, it sounds like pellets work better to apply, and take 2 years to work into the ground. Also, instructions say it’s not good for dogs, my dog is outside a lot.

The main reason to apply lime to a yard or soil is to neutralize an acidic soil. Generally speaking, most all home lawns and gardens do not have acidic soil but rather alkaline, with a pH of about 7.4 and often higher. You mention that you live on a mountain of limestone, so adding more lime is certainly the last thing you should do. Unfortunately, many gardening shows on TV are from the East Coast where acidic soils are much more common. Using lime there is a good idea. Lime is also available in many hardware stores; discount outlet stores and even in some nurseries. Unfortunately, when people see it for sale, they recall perhaps that you are supposed to use it on your lawn or garden, so they buy it and apply it. If you are unsure, the best thing to do is get a soil test done. That will tell you what your soil pH is and tell you if you need lime, or more likely that you should apply elemental sulfur to reduce the alkalinity in your lawn.

Dog spots are caused by a high level of salts that are found in the urine. The salts get so high that plants cannot take up water which will cause the grass to die. You will also sometimes notice that the grass is a darker green color and grows taller right around the dead spot. This will be particularly evident if you have not fertilized your lawn in a while. The solution is dilution – dilution of the salts in the soil. You may want to dig out some of the top few inches of soil in the

dead spot, then replace with fresh soil. Then flush each of the dead spots with plenty of fresh water to help dilute and dissolve the remaining salts and flush them down deeper into the soil profile. You can then sprinkle seed in the bare spots and keep it watered until the new little grass seedlings emerge. If you could somehow give your dog more space to use as a space to “do her business”, that would probably help reduce the dog spots somewhat. Also, fertilizing will help to mask the spots by reducing the green circle around each spot.



Why don’t my Weigela ever bloom? I have moved them to new locations. I haven’t trimmed them. I keep them watered. What about fertilizer? They grow but do not bloom. They are about 3 years old. Thank you.

Weigela are a spring flowering shrub that normally blooms on old wood, but it may also bloom sporadically during the rest of the growing season. It should be planted in a full-sun location for best growth and flowering. Since this plant blooms on wood that grew last year, do not prune it late in the summer, fall or during the winter because you will be removing the tips of the branches that would otherwise produce the flowers. If you want to prune it, wait until right after it is done blooming, when it does bloom that is. Late spring frosts can also damage flower buds and therefore reduce flowering. Be patient, it can take a few years for plants to get old enough to begin blooming.


Spring Care for the Flower Bed

Spring is here at last! Probably the main thing holding plants back are the cold, saturated soils. Windy spring weather is common in South Dakota and the Great Plains so once the wind picks up, that should help to start drying things out. Despite the late spring, some of the earliest spring flowering plants are already blooming but others are still just getting started.

Even though most areas have now had several days up in the 60’s and 70’s, it is still very possible to see temperatures drop down into the mid-twenties at night with early morning temperatures below freezing common. So, even though most of us are ready to see the big spring green-up and lots of flowers blooming it is still rather early. For now, we will have to be content in searching for the first of the pasque flowers to bloom and some of the other early flowers like Chionodoxa, Crocus, Puschkiniaor perhaps some Pulmonaria or Helleborus. Tulips are already popping out of the ground but hopefully the flowers will remain deep enough in the soil a few weeks more to avoid being damaged by spring freezing temperatures.

If your garden or yard is still pretty wet, wait until it dries out so that you do not cause a lot of compaction of the soil by walking on it or driving around on it with your garden tractor and trailer or wheelbarrow. Once our perennial flowers begin to send up new shoots, it is probably time to start doing some spring cleanup. This will be especially important for plants that are the first to grow like cool-season grasses, peonies, the tall sedums or Hylotephylum like ‘Autumn Joy’ and any of the other plants that have lots of tall, old stems that will get mixed in with the new stems as they grow. Once the new growth gets mixed in with the old stems it becomes much more difficult to prune them out. If you don’t prune them out, it can leave the garden looking rather messy. Those old stems and leaves can also be a source of disease spores that can spread to the new growth. Iris leaf spot, for example, overwinters on the diseased leaves from last year. Removing those old leaves before the spores have a chance to spread to the new foliage can slow the re-development of the disease this year.

If you are cutting back the dead stems from last year, try to remove them as close to the soil as you can – dead stubs can be unsightly. However, be careful to not damage newly emerging stems of perennials like peonies. If you break off those new stems, they will not regrow. The new stems of most perennials are more forgiving. If they are mistakenly cut back or frozen off, they will probably regrow, possibly even bushier than they would have had they not been damaged.

It might not be a bad idea to consider doing a top dressing with some compost, thoroughly composted manure or even a light application of fertilizer, perhaps a half pound of 10-10-10 per 10 square feet of bed space. Do not use fresh manure or even manure from an old manure pile because it could contain weed seeds, such as Canada thistle, which you might end up fighting to get rid of for years to come. Whichever one you use, avoid getting it right on top of the plants, but rather scatter it around the baseof the plants. Then give it a good soaking using a hose with a breaker to wash it down into contact with the soil.

You might also encounter areas in your flower beds that look like they are covered with gray mold. The mold could have developed beneath a snow drift or under a pile of leaves. Just use a rake to clean it up as best you can to allow it to dry out and the plants should be OK. I often used leaves to cover tender plants that might freeze out during an open winter. Start raking those leaves back so that the new shoots are able to get some sunlight. If you wait too long the new shoots could be very weak due to the lack of sun exposure. But, if you remove the leaves and other plant debris too early, some of those more tender plants might be damaged by spring freezes. So, it is probably best to do it gradually. Remove enough to expose the new shoots then take off more over the course of the next couple weeks.



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