Timely topics for early September
At this time of year I often receive requests on how to grow trees from seed. The two most common requests are how to start walnuts and buckeyes. These are actually fairly simple to grow from seed, squirrels do this routinely with great success considering the number of walnuts and buckeyes that germinate in gardens and other prepared soils! The trick is to think like a squirrel. Harvest the seeds as soon as they drop and plant them this autumn while the soils are still warm. They will not initiate growth this fall, but germination improves if they are exposed to several weeks of warm temperatures before enduring the winter cold. The planting site should have well-drained soils, gardens really are the best, and cover the soil with a light mulch, straw or leaves that will not mat down. Oak leaves are the best but do not use maple or basswood leaves, nor grass clippings as these tend to mat.
The only trick to growing these trees is removing the husk of the fruit to find the seed. This is not a particularly difficult task with buckeyes; the “buckeye” tends to be easily extracted from the fruit as it naturally splits in the fall, often while on the tree, so it may be as simple as picking up the buckeye seeds (these are the size of a gumball with a hard coat and the characteristic dot or “eye”) and planting them.
It is a little more difficult, and messy, with walnuts. The walnuts should be harvested while they are still firm but green – once they dry and harden they are near impossible to crack. First step, after gathering the walnuts is to change into clothes you don’t plan on keeping as well as wear an old pair of gloves. Next find a hard surface to hammer open the husk. You might not want to use your sidewalk or driveway as removing the husk will produce a lot of dark, oily stain that does not easily wash off of most surfaces. Some people cover the surface with thick cardboard to reduce staining. Once the husk has been hammered apart and the seed extracted, let it dry for a day (and place it where the squirrels cannot find them) then plant. A good rule is to plant the seed; either walnut or buckeye, at a depth equal to three times its diameter. Finally sit back and wait till spring, and if the squirrels have not found your seeds you will probably be rewarded with 50 to 80% germination.
Verticillium wilt (Verticillium dahliae) is appearing again in eastern South Dakota. We seem to have years where we see few trees presenting symptoms and then a year or two where many trees are wilting from the disease. The symptoms can be confusing as many other stresses will cause similar patterns. The most common symptom is wilting and scorched leaves during the hottest and driest time of the summer. While these symptoms can be due to drought, verticillium many only affect a single branch or portion of the canopy, rather than the entire tree wilting. Leaves in the affected area of the canopy may also be stunted.
The reason for the wilting is the sapwood becomes plugged and the affected branches will often have green (in maples) or brown (most other species) streaking in the sapwood. The streaking is often several feet or more down the branch from the wilting so check for the browning nearer the base of a wilting branch. Ash infected by verticillicum wilt rarely show any streaking.
Since wilting can be due to many other agents, the only way to conclusively diagnosis verticillium wilt is to culture the pathogen from a branch presenting symptoms of the disease. The samples need to be cut from 1 to 2 inch diameter branches and should be about a foot long. The branches must be showing symptoms but not have died from the disease.
The presence of the disease does not necessarily mean the tree must be removed. Some trees live for decades with the disease, only having a branch or two die every now or then. Other trees may have the entire canopy wilt and the tree die the same season.
Verticillium is soil-borne so you cannot cure an infected tree and once the tree is removed the pathogen can remain in the soil for up to 15 years. The only effective treatment is not to plant certain trees in soils where the pathogen is known to exist. The most common hosts in South Dakota are: catalpa, elms and maples. Other hosts include: ash, buckeye, coffeetree, corktree, and Russian-olive.
A common phenomenon with a little rain after a dry summer is flowering by some of our spring-flowering trees and shrubs. The flowering of crabapples, lilacs and other trees at this time of year is not a cause for concern. They will still be ready for winter on time, but since some of the flower buds are opening now there will be fewer blooms on the plant next spring.
A common problem at this time of year is the cottonwood petiole gall. Many people have noticed that their cottonwood tree is dropping a large number of yellow leaves. A closer inspection of these leaves will reveal small galls at the point where the leaf blade attaches to the petiole. The galls are the work of a small aphid that has finished its feeding at this time and no control is necessary. Raking the fallen leaves will not reduce the chance of an infestation next year as the galls are now hollow and devoid of insects.
The wooly oak gall is appearing on bur oaks across the state. The wooly oak gall is a fuzzy white to tan globose to elongated gall that forms on the underside of the leaves. It is caused by the feeding activity of Callifhytus lanata, a small cynipid wasp. The galls do not harm the tree and photosynthesis is not disrupted. The galls usually appear on a tree for several years then disappear for another eight or ten years before the cycle begins again. There is no control for this interesting insect.
Deadheading your flowers
By David Graper
SDSU Extension Horticulture Specialist
Cooler temperatures are a sign that autumn is on the way. For many gardeners, the cooler temperatures are a welcome relief from the heat and humidity that sometimes made gardening a little less enjoyable than we would like. Consequently there might be some gardening tasks that got put off for a while. Deadheading flowers might be one of those tasks.
Deadheading is the removal of spent flowers by cutting back the flowering stems to foliage lower down in the plant or in some cases all the way down to the ground; but that will depend on the kind of plant you are working with. If there isn’t any foliage left on the flower stem, as in the case of a plant like a daylily, try to cut the stem down far enough so that you do not leave an ugly stub that is visible above or in the foliage. There are several reasons why you may want to deadhead at least some of your flowers. First of all, the old flowers can be kind of messy-looking. Cutting them off can really improve the appearance of the rest of the plant, even if all that is left is the foliage. At least you won’t have the brown stems detracting from the appearance and form of the plant.
Probably one of the most important reasons to deadhead flowers is that it will often stimulate additional flowering. Many plants will start putting energy into the production of fruit and seed after flowering. This will likely decrease the likelihood that plants will re-bloom. Removing the old flowers and developing fruit and seeds will help stimulate new flowering branches or shoots to develop farther down on the plant to provide at least a partial flush of new flowers in a few weeks. For young plants, removing developing seed heads and fruit will help the plant to utilize more of the carbohydrates it produces through photosynthesis to be used to help build up the plant and give it a better chance to make it through the winter and grow larger next year.
Another benefit of removing the developing seeds is that they will not be allowed to fall to the ground, germinate and grow into new plants, which in some cases might be considered weeds, if they don’t end up growing where the gardener would like more of these to grow. Thankfully many plant breeders are incorporating sterility into the new cultivars they are releasing so what was a great plant does not become a great big weed problem. I recently spent several hours breaking off or digging out four garden tractor wagon loads of globe thistle (Echinops) that had literally taken over the flower bed in front of my home. It had just finished flowering and was loaded with seeds that were nearly ripe. I like this plant for its round blue flower heads but not when it threatens to take over a major part of my garden.
There are of course many plants for which deadheading is not recommended. Those would include plants that have attractive seed heads or fruit. Gas plant (Dictamnus) is an interesting plant that I have growing at home and at McCrory Gardens. I has quite pretty pink or white flowers that under the right conditions emit a flammable gas that can be ignited by a match or lighter – hence the name. Once the flowers fade, it develops a very attractive star-shaped seed capsule which looks good all summer long and even into the winter months, especially when it is coated in frost. Coneflowers (Echinacea) are another plant that has great looking old seed heads in the fall and winter as they are contrasted against the snow. Ornamental grasses are known for their winter interest so are generally not cut back until spring. These are just a few of the plants that are probably left alone after flowering. Another benefit of not cutting them back is that those extra stems will help to catch snow during the winter months to help capture moisture for next year’s growth and also provide some extra winter protection for the plants.