Elms are amazing trees that offer a ton of benefits for homeowners, wildlife, and the greater ecosystem as a whole. From shading properties to feeding animals to reducing runoff water following storms, they are certainly valuable components of our local flora.
However, elm trees do require the proper care and maintenance to thrive and look their best. We’ll try to help you take good care of your elms by outlining some of the key things they need.
Elm Tree Basics
There are more than 30 elm species currently found around the world, all classified in the genus Ulmus. Most are medium to large in size, with a few species reaching up to 100 feet in height. The majority of elms are deciduous trees, which shed their leaves in the winter, though a few are semi-evergreen in mild climates.
All elms have a simple leaf arrangement (the leaves attach to the twig singly), and they tend to have serrated (toothed) margins. Notably, elm leaves have conspicuously asymmetrical leaf bases, with one side drooping lower than the other.
Most elms grow quickly, and they’re capable — at least theoretically — of living for several hundred years in ideal conditions. While they don’t have showy flowers, many elm species have very attractive bark, which helps provide “four-season interest.”
Species Rollcall: Common Elm Trees in Central Oklahoma
Most elms you’ll encounter in Central Oklahoma belong to one of six species, including four that are native to the state and two exotic species, which are often planted ornamentally.
Native Oklahoma Elm Tree Species
You may see any of the four native elm species growing in backyards, natural areas, or alongside roads. These species include:
- American Elm (Ulmus americana): Once the iconic street tree of the Midwest and East, the American elm is a towering, vase-shaped tree that is unfortunately highly susceptible to Dutch elm disease.
- Cedar Elm (Ulmus crassifolia): A drought-tolerant tree that naturally grows on thin soils, the cedar elm is one of the toughest elms and grows well in most urban landscapes.
- Winged Elm (Ulmus alata): Named for the distinctive corky “wings” along its twigs, the winged elm or wahoo is a smaller upland species that can thrive in dry, sandy, or rocky regions.
- Slippery Elm (Ulmus rubra): Named for its mucilaginous (slimy) inner bark, the slippery elm favors moist, fertile soils and provides wildlife with both food and habitat.
Exotic Elm Trees Commonly Planted in Oklahoma
The two non-native elm species commonly found in Oklahoma will usually be limited to private properties. These species include:
- Siberian Elm (Ulmus pumila): An extremely hardy and fast-growing Asian species, the Siberian elm tolerates drought, poor soils, and urban pollution, though it is considered invasive in parts of the U.S.
- Lacebark Elm (Ulmus parvifolia): A graceful, disease-resistant ornamental from China, the lacebark elm is prized for its mottled, peeling bark and small, glossy leaves that often stay green well into winter.
Proper Tree Trimming: Pruning Elm Trees in Central Oklahoma
Every individual tree presents different pruning requirements, which reflect its size, health, vigor, structure, and location, as well as the tree owner’s desires. So, it can be tough to make broad generalizations about how your specific elm trees should be pruned.
With that said, most elm trees need two kinds of pruning:
- Structural pruning when young to develop good form and help encourage balanced crown development.
- Periodic crown cleaning to remove any dead or dying branches.
Homeowners can carry out structural pruning, provided that they have the tools, knowledge, and expertise to do so. However, they’re discouraged from crown cleaning large trees. As a rule of thumb, any pruning work that requires you to reach above your head should be left to professionals.
Additionally, some elm trees may need other kinds of pruning in specific situations:
- Vista pruning may be necessary to improve sight lines around the tree.
- Crown raising provides more space below a tree’s canopy to provide more access beneath the tree.
- Crown thinning, if the tree’s canopy becomes too crowded.
- Crown reductions, which seek to keep a tree’s canopy from outgrowing the space available.
Because these pruning techniques almost always take place high in the canopy and require considerable expertise, they’re best left to professional tree trimmers, like Elion Landscaping & Tree Service.
Hydration: Watering Elm Trees in Central Oklahoma
Most elms are pretty tolerant of varying moisture levels. They’re not like willow trees, which need very moist (bordering on wet) soil, or some upland pine species, which need very dry soil. With that said, it’s imperative that you provide your elms with proper soil moisture levels and note that different elm species have slightly different preferences.
For example, virtually all elms require plenty of supplemental water while they’re young or recently transplanted and trying to establish a healthy root system. Such trees should be provided with supplemental irrigation two or three times per week for at least two to three years.
Mature, established elms, on the other hand, require varying amounts of supplemental water.
American and slippery elms, for example, require relatively moist soil. So, they’ll tend to benefit from some additional water, particularly during extended droughts. Meanwhile, cedar elms, winged elms, Siberian elms, and lacebark elms are native to drier habitats, and they rarely require extra water once established, except during especially prolonged droughts.
Just understand that when providing water to trees, it’s always better to provide long, slow, deep soaks or a relatively infrequent schedule, as opposed to providing frequent, shallow waterings. This is because the former approach encourages trees to develop deeper root systems.
Soil Health: Mulching and Fertilizing Elm Trees in Central Oklahoma
Soil health is crucial for the health of most trees, and elms are no exception. And while each elm species you may have growing in your yard exhibits slightly different soil conditions, most will thrive in relatively similar conditions.
A few important things to keep in mind when trying to provide your elms with the best possible soil include:
- Aim for a neutral pH level. Some elm species, like slippery elms, thrive in slightly acidic soils, while cedar elms tend to prefer slightly alkaline soils. However, most elms native to Oklahoma or commonly planted in the region can thrive in neutral soil, with a pH of around 7.0.
- Always use mulch when possible. Natural, organic wood mulch provides a wealth of benefits for elm trees, ranging from moderated soil temperatures and better moisture retention to protecting your roots from mower damage and limiting competition from turf grass.
- Apply mulch correctly. If you do use mulch, be sure that you apply it correctly. This means putting down a 2- to 4-inch-thick layer of mulch over the entire root system (to the edge of the canopy), while leaving a small gap around the trunk, so that mulch doesn’t trap moisture and encourage decay.
- Only apply fertilizer after conducting a soil test. You should never fertilize trees haphazardly; this can cause more problems than not fertilizing them at all. Instead, you must identify the specific nutrient deficiencies present in the soil and select a fertilizer that addresses them.
If you keep these things in mind, you’ll likely maintain high-quality soil that allows your elms to thrive.
Common Elm Tree Pests and Diseases in Central Oklahoma
Unfortunately, there are a variety of pests and pathogens that can threaten your elm trees. A few of the most important examples to be aware of include:
Dutch Elm Disease / Elm Bark Beetles
Dutch elm disease (DED) is a lethal vascular fungus (Ophiostoma spp.) that clogs a tree’s water-conducting tissue, causing rapid wilting and death. It spreads primarily through native and European elm bark beetles, which carry spores from infected wood to healthy trees, but it can also be transmitted through root grafts between adjacent elms.
Dutch elm disease is treatable, though treatments can be expensive. This is part of the reason that many homeowners opt to plant elm species that are resistant to the disease — such as Siberian and lacebark elms — rather than American, winged, and slippery elms, which are all quite vulnerable.
Bacterial Leaf Scorch
Caused by the bacterium Xylella fastidiosa, bacterial leaf scorch blocks water movement in the xylem (wood) during hot, dry weather. This causes the leaves to develop brown, scorched margins during the heat of summer while often remaining attached.
The symptoms of bacterial leaf scorch tend to return and worsen each year. There is no cure for the disease, and it generally becomes fatal over the years, eventually triggering the need for removal. However, it can be managed and its progression slowed by supporting the tree’s overall health.
Elm Yellows
A phytoplasma infection that kills the inner bark (phloem) of elm trees, this disease often causes sudden leaf yellowing and drooping. Unfortunately, death often follows, sometimes in as little as a year.
Elm yellows spreads underground through root grafts and above ground by leafhopper insects, making it difficult to contain. And because there is no effective chemical treatment, removal of infected trees (and their root systems) is the only reliable way to protect any other elms you may have in the area.
Verticillium Wilt
Caused by a soil-borne fungus that invades a tree’s roots and clogs its vascular system, verticillium wilt causes branch dieback and brown streaking in the sapwood. Symptoms can occasionally be patchy, and they usually include marginal leaf scorching or sudden wilting on individual limbs while the rest of the crown appears healthy.
There is no curative treatment, and management focuses on pruning out affected branches, improving soil health, and planting resistant species when replacement is necessary. Because the pathogen lives in the soil, replanting another elm or other susceptible hardwood in the same spot can lead to reinfection.
Anthracnose
Caused by a group of fungi that thrive in cool, wet springs, anthracnose infects young leaves and shoots. It causes irregular brown blotches, distorted new growth, and premature leaf drop. The disease often appears soon after budbreak, when prolonged high humidity levels keep a tree’s leaves wet for many hours.
Repeated infections can weaken trees over time by reducing photosynthesis and stressing new shoots, especially on young elms. However, the disease itself is rarely fatal.
Elm Leaf Beetle
This small yellow-green beetle skeletonizes foliage, leaving leaves lace-like and prone to early drop. Multiple generations per summer can heavily defoliate trees, leading to stress and making them more vulnerable to other pests and diseases.
Control typically involves monitoring in late spring and, if needed, targeted insecticide treatments or horticultural oils timed to the first hatch of larvae.
While these insects and diseases can cause trouble for your trees, just remember that you can help give your trees the best chance of fighting off these threats by supporting their overall health. So, ensure that your trees get the right amount of water, receive professional pruning when necessary, and have a thick layer of mulch over the roots.
Let Elion Landscaping Provide the Care and Maintenance Your Elm Trees Need!
Whether you have a single lacebark elm in your front yard, a cluster of cedar elms along your property line, or you’re lucky enough to have a surviving American elm in your backyard, Elion Landscaping can provide the kind of care your elm trees need to thrive and look their best.
From fertilization to mulching to pruning, we can help maintain your elm trees and keep them healthy for years to come. We can even install new elm trees for you, if you have an open space in your yard that would benefit from a tree.
Contact us today to discuss your elm trees and start getting them the care they deserve!
Sources and References
- Oklahoma State University Extension. “American Elm (Ulmus americana) Plant Profile.” Plant Identification Profiles, Oklahoma State University Extension, Stillwater, OK. https://extension.okstate.edu/programs/plant-id/plant-profiles/american-elm/
- Oklahoma State University Extension. “Cedar Elm (Ulmus crassifolia) Plant Profile.” Plant Identification Profiles, Oklahoma State University Extension, Stillwater, OK. https://extension.okstate.edu/programs/plant-id/plant-profiles/cedar-elm/
- Oklahoma State University Extension. “Lacebark Elm (Ulmus parvifolia) Plant Profile.” Plant Identification Profiles, Oklahoma State University Extension, Stillwater, OK. https://extension.okstate.edu/programs/plant-id/plant-profiles/lacebark-elm/
- Oklahoma State University Extension. “Winged Elm (Ulmus alata) Plant Profile.” Plant Identification Profiles, Oklahoma State University Extension, Stillwater, OK.
- https://extension.okstate.edu/programs/plant-id/plant-profiles/winged-elm/
- Oklahoma State University Extension. “Slippery Elm (Ulmus rubra) Plant Profile.” Plant Identification Profiles, Oklahoma State University Extension, Stillwater, OK.
- https://extension.okstate.edu/programs/plant-id/plant-profiles/slippery-elm/
- Oklahoma State University Extension. “Siberian Elm (Ulmus pumila) Plant Profile.” Plant Identification Profiles, Oklahoma State University Extension, Stillwater, OK.
- https://extension.okstate.edu/programs/plant-id/plant-profiles/siberian-elm/
- International Society of Arboriculture. Proper Mulch Technology. ISA / Trees Are Good.
https://www.treesaregood.org/Portals/0/TreesAreGood_Proper%20Mulch%20Tech_0321.pdf - Arboriculture & Urban Forestry. “Arboriculture & Urban Forestry Volume 4, Issue 7, Page 157.” International Society of Arboriculture.
https://auf.isa-arbor.com/content/4/7/157
