What could be causing my grape leaves to curl?

Q: Some of the leaves on my 2-year-old Thompson Seedless Grapes plant have started to curl at harvest. There is more curling on the newer leaves. The older leaves are OK, and the curling is only on one side of the plant. The Red Flame Grapes plant (also 2 years old) was planted adjacent to the Thompson Seedless. They are OK with no sign of curling or cupping.

Each plant has two 1-gallon drippers, so each plant receives 6 gallons of water per week. Is that sufficient? The plants are in a raised bed approximately 18 inches deep of premium mulch/soil. Both of the plants have several bunches of grapes, and I have already pinched off the bottom third of each grape bunch.

A: Six gallons a week is not enough water for grapes, in my opinion, but watch the plants and they will tell you. If you are getting some good vigorous growth from 6 gallons, then it is enough, and I would not change it. Grapes are normally deep-rooted plants. I would prefer that they get more water all at once and then hold off. You are watering to a depth of maybe 18 inches or so in most of our soils, so watering three times a week during the summer on grapes with this rooting depth makes sense to me. If they run out of water in the summer, then add more drip emitters.

After grape harvest, cut back on the frequency of your application but not the amount you have selected. You need to maintain adequate soil moisture during fruit production and up to harvest. That’s critical. After that, you can stress grapes or any fruit-bearing plants.

Now, regarding leaf cupping. Leaf cupping or curling usually has to do with weed control or water. Grapes are notorious for weed killer damage. If weed killers were used near the grapes on a windy day that is a big no-no. I look at tree branch movement to judge whether to spray. If the tree branches are moving at all, I should not be spraying.

Q: How is Krauter Vesuvius plum as a yard tree? My neighbor has one. It’s 20 years old and not real big. It flowers for a couple of weeks in the spring.

A: Krauter Vesuvius, along with Thundercloud, is one of the older red-leafed flowering plum trees. As true of all fruit trees, it flowers only in the spring.

The difference between a red flowering plum tree and a Krauter Vesuvius is its consistency in color, shape, size, etc. It generally doesn’t get much above 20 to 25 feet tall, with about the same width. If you buy a Krauter Vesuvius plum tree it should be grafted, not started from seed. You should see a graft union (dogleg) near the soil surface. Its presence will tell you it’s truly a Krauter Vesuvius.

It is not much different in its need for water than other plum or fruit trees. It probably requires about 5 feet of water each year with some protection from the wind and sun in a mature orchard. As with all flowering plums, put it in the mesic category in its need for water. It will do well in lawns, but it is not a desert tree.

Q: Our family owns an unimproved lot just outside of Duck Creek in Southern Utah. The elevation is approximately 8,500 feet. The last three winters have not been kind to our trees. With the combination of heavy snowfall and strong winds, we had a major blowdown of dead snags and live trees.

A ranger mentioned a root fungus that has affected the local population of pines. We are considering clearing the area of downed trees for access to the property but, more importantly, to provide a defensible area and elimination of fuel for potential fires.

We would like to scatter local wildflower seeds on our lot. I have looked at sources for seed and researched the names of local plants. Many of these species will take a year or so to bloom and require some soil preparation and germination. However, there doesn’t seem to be a definitive source for both information and product.

I was raised in Northern California, and many years ago my parents found bulk seed provided by the state for seeding the hillside behind our property there. California golden poppy, lupine and wild oats come to mind.

A: This is a touchy topic. Introducing nonnative species in that area could be a problem. We want to be very careful about adding nonnative plants to a primitive or semiprimitive area. New species of plants that can spread from their own seed or other plant parts could be a big weed problem and create even more fuel for fires.

I would be sure to check with your Natural Resource Conservation Service representative or a local forester or ranger.

Information on native plant species will be a first step to understanding what you might plant there safely. Most of these are perennial species that can reseed themselves, with a couple of annuals and biennials that could self-propagate.

When you assemble your list, run it by your local forester since it might contain plants they would discourage. For instance, bull thistle is a plant I might consider invasive and not one that you want.

Bob Morris is a horticulture expert and professor emeritus of UNLV. Visit his blog at xtremehorticulture.blogspot.com. Send questions to Extremehort@aol.com.