In some ways July and August developed backward this year, with midsummer mildness and then hot muggy weather returning only in late August — just in time for those schools that have no air conditioning. Certain developments for the plant world are right on time now though, from disorders such as physiological leaf scorch to infectious diseases such as tar spot of maple and Guignardia leaf blotch of buckeyes.
Naturally, there are many more pleasant happenings for our eyes, such as fruit development on wild impatiens, Kousa dogwood, pawpaw and sweetbay magnolia. There are even the “fruiting bodies” of many mushrooms, such as the common honey mushroom (Armillaria mellea).
Let us take a look at what is happening now, starting with one of the trees, shagbark hickory, that is a feature of the woods in the new Carolyn Ludwig Mugrage Park in Medina County’s Granger Township, as well as the many fine specimens to be found in Johnson Woods State Nature Preserve near Orrville, many of the Metro Parks Serving Summit County, and even in my backyard.
Shagbark hickory
Shagbark hickory (Carya ovata) is a large (70- to 90-foot) native tree for Ohio and the eastern U.S. It’s less prominent in the south.
It has compound leaves with mostly five leaflets, monoecious flowers (male and female flowers on the same plant but separated), and dramatic shaggy plates of bark on older trees. Large foliose terminal buds are a good characteristic and jagged branch structure is dramatic in winterscapes.
Shagbark hickory thrives in moist, well-drained acid soils, but often predominates in upland sites due to its comparative advantage of excellent drought tolerance.
Sweet nuts are a source of food for squirrels and many other animals. Some folks use the sap for specialty woodsy syrups. Green wood is used for smoking meats, cut timber for furniture, tool handles and other uses.
It readily hybridizes with other Carya species such as Carya illinoiensis (pecan) and Carya laciniosa (shellbark hickory). It has limited formal landscape use since it has a tendency as a “dirty” tree, dropping numerous twigs, small branches and leaves.
Tar spots of maple
At Diagnostic Workshops last month, Ohio State University Extension folks frequently displayed samples of the two tar spots of maple. Rhytisma acerinum causes dense, tarry spots, mostly on silver maple and red maple, while Rhytisma punctatum causes tiny “punctate” spots which diffusely coalesce into inch-size or larger roundish spots, mostly on Norway maple.
On Norway maple this tar spot can cause considerable leaf drop in late July and August, resulting in great concern to homeowners, though typically little long-term health problems result with this late-season problem.
The Rhytisma fungi overwinter in fallen leaves, so if there is a concern, raking up the leaves (followed by removal from the landscape or composting) can be effective to limit tar spot incidence.
An unsightly disease
Guignardia leaf blotch of buckeyes and horsechestnuts is fairly severe this year and symptoms were quite evident on susceptible buckeyes, horsechestnuts, and some of their hybrids in late August.
Symptoms include large irregular reddish-brown lesions with surrounding yellowed tissue on leaves, often badly disfiguring foliage by early to mid-summer. Leaves often curl and brown and, by August, the overall plant often looks as if it was blow-torched.
Early leaf drop also occurs. The problem is enhanced by wet foliage conditions. The disease is not a problem in drier U.S. sites in the west.
Initial infections are in the spring from fungal spores produced in infected leaves from the past year. Moist conditions enhance infection cycles.
Fortunately, the disease is not a serious problem for buckeyes and horsechestnuts as the trees have produced most of their food through photosynthesis by the time foliage is seriously affected.
It is quite unsightly though. Practice sanitation by cleaning up infested foliage at the end of the season to help prevent the overwintering of the fungus. Or plant the bottlebrush buckeye shrub Aesculus parviflora which has excellent genetic resistance to this disease, or red buckeye (Aesculus pavia) which has pretty good resistance — and scarlet flowers in spring.
Armillaria fungus
This fungus (Armillaria mellea) goes by many names. It is an opportunistic fungus that infects many plants, especially stressed plants.
You see it in woods in one of its forms, as the shoestring-fungus, so named for the hardened, blackened masses of fungal mycelial strands that help the fungus survive.
You will see these shoestrings, also called rhizomorphs due to their root-like shape, on the bark of dead and declining trees and logs in the woods, along with the precursor of the rhizomorphs — fan-like whitish fungal strands under the bark of the tree.
When this fungus mates its fruiting bodies are known as honey mushrooms, and this is what many people are seeing in profusion in Ohio woodlands, often ringing the base of trees. Remember though, do not eat any mushrooms in the woods unless you are absolutely sure of their identity. There are old mushroom hunters, and there are bold mushroom hunters, but there are no old, bold mushroom hunters.
Wild impatiens
Jewelweed, touch-me-not, the orange-flowered Impatiens capensis and the yellow-flowered Impatiens pallida are common denizens of Ohio woodlands.
The names are telling. They are impatiens, and you are reminded of this when they wilt down during the day and revive at night, just like bedding impatiens.
Water beads on the hydrophobic leaves, which glisten jewel-like in the sun. Most wonderfully, if you lightly grasp the mature seed-pod, you will engage the spring-like mechanism that shoots the seeds from the pod, dispersing them outward to find new ground.
Jim Chatfield is a horticultural educator with Ohio State University Extension. If you have questions about caring for your garden, write: Jim Chatfield, Plant Lovers’ Almanac, Ohio State University Extension, 1680 Madison Ave., Wooster, OH 44691. Send email to chatfield.1@cfaes.osu.edu or call 330-466-0270. Please include your phone number if you write.