More recent horticulture questions and answers

Horticulture

Dogwood didn't bloom

Two years ago in the fall I bought a white Cherokee Princess flowering dogwood from a reputable nursery. I planted it in full sun on a slight incline for good drainage. I watered frequently the first year. It grew substantially and even bloomed the next spring. This spring it was loaded with buds that never opened, thus, no leaves. The limbs are green and the tree, with the exception of the buds, looks viable. What is the problem?

The only explanation that comes to mind is that the buds were damaged by a spring freeze event. If the tree is planted on a south-facing slope, it may have begun to bud out a little earlier than most dogwoods, therefore making the buds susceptible to a spring freeze. If so, you should be seeing new vegetative growth coming from the twigs by now.

Chris Starbuck
State Extension Specialist
Woody Ornamentals

Native plant source

Where can I get a list of Missouri nurseries that sell native wild flowers and trees such as witch hazel, redbud, dogwood and hawthorn?

Most local retail nurseries will carry redbud, dogwood and hawthorn. You might check Grow Native, www.grownative.org, to find local nurseries selling some of the more unusual things you are looking for.

Chris Starbuck
State Extension Specialist
Woody Ornamentals

Ajuga reptans seed

I have been having trouble finding a wholesaler of ajuga reptans seed in bulk. Are there any in Missouri?

The reason you can't find a seed supplier is that growers propagate by cuttings or divisions. This is a plant that is very easy to root from cuttings. You should be able to find a supplier who will sell you rooted cuttings in small plug trays.

Chris Starbuck
State Extension Specialist
Woody Ornamentals

Exposed tree roots

We have a tree in our front yard with exposed roots that are somewhat unsightly. Is it adviseable to plant flowers or do any other type of landscaping around the tree? Is ground cover OK? If so, what types?

First, the reason why the roots are growing on the surface is that the soil is shallow and there is no way for the roots to go but up, when they increase in diameter. Maples are the most common culprits, but many tree species will do the same thing. People often ask whether the roots can simply be cut off near the trunk or whether they can be covered by soil to allow mowing under the tree. My answer is that neither of these options is good for the tree. Cutting off a main root will cause serious stress, since it may remove up to 30 or 40 percent of the root system immediately. Covering the roots with more than 3 or 4 inches of top soil may suffocate the roots near the surface or, if the new soil has a high clay content it may suffocate cells in the bark of the roots, leading to root rot problems. Also, this is a temporary fix, since the roots will continue to increase in diameter and eventually push their way to the surface again through the added soil.

So, what to do. In my opinion, the answer is to stop fighting mother nature. Nobody mows under trees in the woods. I recommend mulching the entire area under the tree and planting shade tolerant perennials such as Epimedium, Pulmonaria, Ferns and Hostas in pockets of soil between the roots. A limited amount of soil can be brought in, but not more than a few inches in depth. Ground covers such as English ivy can also be used to reduce maintenance requirements. Plants under the tree canopy will have to be watered frequently due to competition from tree roots, but in the end, the area will have a nice, woodsy feel to it. And, there will be less lawn to mow.

Chris Starbuck
State Extension Specialist
Woody Ornamentals

Sidewalk makeover

What kind of materials can I use to create a mosaic design on my sidewalk to make it more attractive, but safe to walk upon?

It is not recommended that anything such as a tile mosaic be applied directly to the sidewalk surface. The winter temperatures here in Missouri do not contribute to a long-lived solution of the type you propose. Such an application will be highly susceptible to cracking from repeated freezing and thawing. One alternative is stepping stones that could be decorated in this fashion and then moved to the indoors in freezing weather. Flagstone set in mortar, brickwork set in mortar, and particularly applications like mosaic applied to existing concrete are regular maintenance headaches. Of course, you can do whatever you wish. However, because of the susceptibility to cracking due to freezing, these types of finishes are not recommended.

If this type of "textured" finish is what you are after, then an application far less prone to maintenance problems over time due to freezing would be exposed concrete. . .where you can select the type of aggregate (stone or gravel) to have exposed. Concrete is poured with a finish of selected stones worked into the surface of the concrete. After the concrete begins to cure (typically an hour or so, depending on the air temperature), the concrete is hosed down to expose the aggregate at the surface. The surface is far rougher than terrazzo but is quite durable and relatively maintenance free when constructed properly.

Bobbi Hauptmann
Department of Environmental Design