By: Christy Dipman
Blog Post: http://www.ksuhortnewsletter.org Video of the Week: Composting – Making Black Gold
Still Time for Salad Garden
Plant salad crops such as lettuce, radishes, spinach, turnips, mustard and other greens from mid-August to early September for a fall harvest. Plant slightly deeper than you did in the spring. This will keep the seed slightly cooler though still warm and the soil should retain moisture longer. Water frequently (if needed) until seedlings start to emerge — which should be fast with our warmer soils. Watering heavy soils can sometimes cause a crust to form. This can be prevented by a light sprinkling of peat moss, vermiculite or compost directly over the row. Reduce watering frequency after plants emerge. Plants may need to be protected from hungry rabbits and insects. (Ward Upham)
Peonies with the “Measles” and Powdery Mildew
The weather this summer has resulted in many peonies catching the “measles” and/or powdery mildew.
Measles: Measles is a disease, also known as red spot, that causes distinct, reddish-purple spots on the upper leaf surfaces. These spots often coalesce and become large, reddish purple blotches on the upper leaf surfaces but are a light brown color when viewed from the underside of the leaves. The spots on stems will merge and form streaks that are reddish brown.
Powdery Mildew: Plants infected with powdery mildew look like they have been dusted with flour and can lead to death of the leaves. This disease isn’t as common in Kansas than Measles but does show up at times.
Sanitation is the best control for both these diseases. Remove all diseased tissue, including stems, at the end of the growing season.
Actually, all foliage can be removed in mid-August with no harm to the plants as the plants will be essentially dormant. Foliage that has already died should be removed now.
Mulch that contains plant debris should also be discarded and then replaced with fresh mulch. Reducing the source of the inoculum will reduce the chances of another severe outbreak next year. (Ward Upham)
Stress to Trees and Shrubs is Cumulative
Stress is cumulative. In other words, trees and shrubs can be affected by stresses that happened up to several years in the past. Recent stresses in Kansas include winter damage as well as the extremely dry winter of 2017-2018 which often resulted in damaged root systems. This damaged root system may have been further weakened due to too much rain this spring. The excess water harmed root systems due to saturated soils driving out oxygen. Roots need oxygen as much as they need water. Though the roots were able to keep up with moisture demands during the cooler spring weather, they may not have been able to keep up when the weather turned hot and dry. Such trees and shrubs may suddenly collapse and die or slough off branches they can no longer support. I have never seen lilacs collapse due to stress like they have this year.
This does not mean that all of our plants are doomed. As a matter of fact, plants that have survived thus far into the growing season will likely make it. Also, some plants are just better adapted to our tough Kansas conditions and have suffered little to no harm. However, it is a good idea to check the overall health of your trees. So how do you tell?
One of the most important clues in determining the health of your trees is the amount of new growth that tree has produced. A healthy tree should have a minimum of 4 to 6 inches of new growth each year and usually much more. Check branches with the tips in the open and not shaded by the tree itself. Anything less than 4 inches on the majority of branches suggests the tree is under a great deal of stress.
So, how do you tell where the new growth stops? Look for a color change in the stem. New growth is often greener than that from the previous year. There is also often an area of what looks like compressed growth where growth transitions from one year to the next.
Lastly, look at leaf attachment. Leaves are only produced on current seasons’ growth. Therefore, new growth stops where leaves are no longer attached directly to the twig but to side branches. However, pay attention as leaves may be appear to be attached directly to last year’s growth but are actually borne on short spurs. If you look closely, you can tell the difference.
All this clue tells you is whether a tree is under stress or not.
It does not tell you what is causing or has caused poor growth. This year, the most common cause by far is environmental stress caused by the excess rain this spring.
So, what do we do for trees under stress? The most important practice is to water as needed. See last week’s newsletter for information on proper watering practices. (Ward Upham)
Plants for Late Season Bloom
Landscapes are often drab this time of year. You can add interest to your home by planting shrubs that flower later in the growing season.
Consider one or more of the following.
Rose of Sharon (Hibiscus syriacus) is a tall shrub that produces single or double flowers. Colors range from white to red, purple or violet, or combinations, depending on the variety.
Crapemyrtle (Lagerstroemia indica) are dwarf-to-tall shrubs or trees. They are not reliably winter hardy in Kansas and often die back to the ground. Crapemyrtle flowers on new wood, so plants pruned (or
killed) to the ground while dormant in late winter or early spring will bloom later the same year. Flower color varies from white, pink, to purple or deep red on different plants.
Bluebeard (Caryopteris x clandonensis) is also known as blue-spirea, blue-mist shrub, or caryopteris. It usually is found with blue flowers, but some cultivars have a bluish-violet to violet flower color. Plants are usually cut back in late winter or early spring.
Flowers are borne on the current season’s growth.
Sweet Autumn clematis (Clematis terniflora) is a vigorous vine with large masses of small, white flowers that have a wonderful fragrance. Be careful with this one; it can easily outgrow its bounds. It is often a good idea to cut it back to the ground in early spring.
Davidiana clematis (Clematis heracleifolia var. Davidiana) is a bush-type clematis with small but interesting violet-blue flowers.
Female plants bear interesting fluffy seed heads into the winter. This clematis needs to be cut back to the ground each year to help maintain the shape of the plant.
The PeeGee hydrangea (Hydrangea paniculata Grandiflora) is a somewhat coarse plant that develops large clusters of white flowers. It can be trained into a tree-like form. (Ward Upham)
Tubakia Leaf Spot of Oaks
This leaf spot disease of oak is showing up in the Wichita area.
Members of the red oak group are more likely to be affected than those in the white oak group, but members of both groups are showing symptoms.
Red oaks often have distinct round spots as well as dead areas that follow the veins.
White oaks also have the dead areas that follow the veins and large blotches of dead tissue but lack the distinct spots. Leaves severely damaged may drop. However, trees rarely lose enough leaves to harm the health of the tree. No fungicide sprays are recommended. (Ward Upham)
Contriubtors: Ward Upham, Extension Associate
Division of Horticulture
1712 Claflin, 2021 Throckmorton
Manhattan, KS 66506
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