Trees, shrubs and weather, oh my!

By |  February 10, 2020 0 Comments
Photo: John C. Fech

Trees tolerant of periodic flooding include baldcypress. (Photo: John C. Fech)

When a fairway or green turns off-color or loses density, what do you do? You usually get down on your hands and knees with a hand lens and inspect the leaves, crowns and roots, looking for abnormal appearances. You also consider recent pesticide or fertilizer applications, traffic patterns and of course, weather. Putting all of this together often yields an initial diagnosis and course of remediation. The same course of action is appropriate for woody plants in the golfscape.

With trees or turf, weather can cause hard-to-determine damage. It’s a major influence, with nothing like it terms of impact. Why?

⦁ It’s multicomponent: winds, flood, hail, heat, drought, sun, rain, snow, ice.
⦁ It’s all-season and ever-present: There’s no break from the weather.
⦁ It’s dramatic: Extremes are seemingly commonplace these days.
⦁ It’s a mimic: Weather-related maladies often are difficult to diagnose because they can closely resemble insect- or disease- related injury causes.

Weather extremes can both cause problems or encourage healthy growth. When “bad weather” or “adverse environmental conditions” are brought up, it’s automatically considered to be the cause of an unhealthy group of plants. On the other hand, mild weather — or a lack of extremes — generally is considered to result in healthy, well-functioning plants.

There are some “tough as nails” plants such as eastern red cedar, coreopsis, yarrow and Osage orange that perform well despite drastic fluctuations, but significant fluctuations mostly cause headaches for those caring for ornamental plants. Success for any planting means knowing how well-adapted a particular species is to extremes, especially in terms of soil moisture and temperature.

Bad weather is a tough thing. There’s absolutely no control. Mother Nature is not going to provide two hours of gentle rain three to four days a week at 4 a.m. Instead, our weather efforts should focus on preparation, not control.

Prevent weather damage: General guidelines

We prepare for weather influences generally and specifically. Four actions can condition plants to be as sturdy and well-healed as possible before weather extremes begin to degrade their health.

Photo: John C. Fech

Proper mulch placement in the golfscape. (Photo: John C. Fech)

  1. Choose well-adapted trees and shrubs. Each USDA hardiness zone sets some guidelines for selecting plant material. Also, microclimates exist in the golfscape, created by slope, shade and wind blockage (or lack thereof) that can have dramatic influence. For example, a redbud may be adapted to zone 5, but if planted in an area open to wind, struck by afternoon sun and on a slope that limits regular water infiltration, it likely will fail. If placed in afternoon shade on a gently sloping site, it likely will succeed. For specific information on these subtleties, consult local Extension professionals and botanic gardens.

  2. Mulching provides many benefits for trees, shrubs, groundcovers and flowers. Organic materials such as wood chips and pine needles help suppress weed growth, retain soil moisture and moderate temperatures, creating suitable growing conditions for roots. As mulches break down, organic matter disperses into the soil profile adding humus, further enhancing soil health.

    Photo: John C. Fech

    Use canvas attachment fabrics when staking. (Photo: John C. Fech)

  3. Stake trees planted in persistently windy sites. It’s highly desirable for trees to move slightly after planting as this encourages stabilizing root growth. If the wind is strong and constant, how- ever, the opportunity for this to occur is lost. In these areas, using a T-post and loosely tied canvas material around the trunk aids in proper development of the root system, girding it for the long haul.

  4. Good bed design, specifically separating turf from ornamentals, is perhaps the most important general prevention standard. Trees and shrubs commingled with turf commonly are overwatered and overfertilized, especially in the moderate-to- high course areas. Again, depending on species, most woody plants need about a third of the water and fertilizer that fairways and areas surrounding tees need. Beds created in well-defined masses and watered and fertilized on a different schedule are well prepared for weather extremes.

Repairing weather damage: General guidelines

Whether it’s a major life event or just an unfortunate incident, acceptance is necessary to move forward. Weather events on golf courses are much the same. You have to let them soak in to your cognitive functioning to start recovery.

Once this acquiescence takes place, the repair process moves to observation and evaluation of symptoms. Asking “What do I see?” and “Was this here before the event?” is helpful. Noting details like a leaning tree — and comparing it to your recollection — is in order. Was it leaning that much before, or has it worsened?

Symptoms often point to a weather-related causal agent. These influences can be easily discernible or quite nebulous. Getting help from fellow superintendents, consultants and university Extension specialists is a good step for hard-to-figure-out symptoms. After the diagnosis is confirmed, it’s time to assemble control and restoration options, eventually choosing the best option among them.

Common weather influences

There are at least nine specific weather influences superintendents must deal with. The influence is different in some cases, but the care actions are the same.

Dormancy breaks/frost

Warm winter temperatures often cause dormant plants to break dormancy earlier than desirable. They will “break bud” and begin to grow during brief periods of warm temperatures. When temperatures soon drop to normal levels, damage occurs to newly emerged plant tissue. Frost effects are similar, occurring with colder-than-normal temperatures after vegetative plants have been installed or woody plants are growing on schedule.

Location often plays a role in this type of damage, so preventive actions include choosing specimens that are well adapted to the course’s USDA hardiness zone, paying attention to overnight weather forecasts, bringing potted plants indoors if temperatures are forecast for 39 degrees F or lower, watering woody plants and ground beds in late fall so they enter winter moist (not soggy or dry), avoiding fertilizing roses and herbaceous perennials and covering susceptible low-growing plants with sheets, blankets or tarps. Corrective actions include allowing damaged leaves to fall from the plants naturally, cutting off blackened stems with a bypass hand pruner or lopping shears, avoiding fertilization until the plants recover and keeping the soil evenly moist.

Photo: John C. Fech

Drought effects are enhanced on slopes in the golfscape. (Photo: John C. Fech)

Drought

Drought is extended precipitation deficiency, usually lasting a season or more. It’s often associated with warmer-than-normal temperatures and is much easier to prevent than cure.

Drought prevention includes identifying drought-prone plants and replacing them with tolerant ones, mulching with wood chips to retain soil moisture, limiting competition from weeds, water- ing thoroughly and evenly, clustering ornamental plants with similar water needs together in beds separated from turfgrass and evaluating the plants’ importance.

Removal of susceptible plants is a good preventive step in some cases. Recovery from drought is difficult and takes time. Examine stems to determine which have desiccated, and remove damaged portions. During the growing season, avoiding fertilization assists recovery until thriftiness recurs, keeping the soil moist (not soggy), followed by applying 2 inches of wood chips to keep roots cool and moist.

Flood and heavy rain events

Ornamental plant roots need oxygen just as much as they need water. When the voids between soil particles fill with water for extended periods, plants become stressed and begin showing symptoms such as leaf-yellowing and drooping stems/leaves.

Site selection and choosing plants that tolerate periodic flood- ing are the best preventive steps, as well as installing bioswales, rain gardens and low berms that help slow water movement, allowing it to soak in and redirect rainwater and limiting flooding potential. Regular core aeration of turf adjacent to ornamental beds is helpful as well. Because root damage usually occurs with extended soil moisture, I recommend contracting with an ISA- certified arborist to spot symptoms of root rot and catastrophic failure. Initially after flooding, pull back the mulch layer to help bring soil moisture to a healthy level.

Until fully determining the extent of root damage, avoid fertilization and probe the soil periodically to know when to reapply mulch to keep newly developing roots moist, not soggy or dry. Some ornamental plants don’t show symptoms of flooding dam- age until the year following the weather event. Documenting this is helpful in future management decisions.

Frequent light rain events

Photo: John C. Fech

Diplodia tip blight, rhizosphaera needle blight, apple scab and cedar apple rust are encouraged by frequent, light rainfall events. (Photo: John C. Fech

Periods with many light-rain events can be quite problem- atic. They often cause heavy disease pressure as the localized environment is enhanced.

Preventing rainfall is impossible, but monitoring it will help manage pest populations as the season progresses. Choosing dis- ease-resistant cultivars of trees, shrubs, perennials and annuals often results in lighter disease symptoms. For example, there are approximately 500 cultivars of crab apple, approximately half of which are susceptible to fire blight, cedar apple rust and/or apple scab; the other half is resistant. Adequate air circulation around specimens through proper spacing helps prevent these maladies, and consulting a respected landscape designer/architect is worth the cost versus dozens of fungicide applications each year.

Corrective actions to respond to damage from pathogens and frequent light rain include removing highly susceptible plants, replanting with disease-resistant cultivars, amending flower bed soil to facilitate drainage and appropriate fungicide application to properly placed/highly functional/good-condition plants.

Hail

Hail forms when rain/ice particles are carried in the updrafts and downdrafts of thunderstorms, then collide and freeze onto one another, growing into larger pieces of ice. Hailstones damage leaves, stems and fruits. The size of the hailstones, the amount of hail, time of year and wind speed play a big role in the amount of damage.

Photo: John C. Fech

Hailstones can cause major injury to tree limbs. (Photo: John C. Fech)

Superintendents’ options to prevent damage to woody plants are limited, but you can bring potted trees, shrubs and patio planters into covered areas until the hail threat has passed. You can cover certain highly prized plants with floating row covers. Recovery from hail damage involves hiring a certified arborist to remove heavily hail-damaged tree limbs and broken perennial and shrub stems. Leaving a few lightly damaged stems encourages seasonal photo- synthesis, as does replanting badly damaged annuals. Hail is a major stressor. General recovery means avoiding fertilization, keeping soils evenly moist and mulching with 2 inches of wood chips, as well as monitoring for pathogenic-and mechanical-cankers.

Ice/snow

Ice forms, of course, when liquid precipitation falls on surfaces having temperatures below 32 degrees F. Higher ice thickness and wind speeds increase damage potential.

Pruning, or “training,” early in a plant’s life prevents ice dam- age. A strong tree and branch structure goes a long way toward the goal. Woody plants that have been rounded or topped are sus- ceptible to injury because of the weak branch angles that develop from these procedures. You can lessen snow damage from mice, rabbits and other four-legged critters by installing hardware cloth or PVC drain tiles, especially on specimens under five years old. Once ice forms on branches, wait until it melts off naturally before attempting corrective action. After growth resumes in spring, follow the general recovery steps for hail.

Tornado/high winds

Storms with high winds uproot trees, cause plant material to fall on other plant parts, break or crack branches and cause other injury that reduces plant life span, pest susceptibility and vigor.
In addition to the preventive steps for ice and snow, a good “before the storm” step is to target prune to remove co-dominant leaders, broken limbs and diseased tissue. Avoiding root masses with twisted and tangled roots encourages development of wide, well-branched and strong root systems that can resist uprooting, which is why close inspection during planting is so important.

In addition, place roots at or slightly above grade to greatly de- crease the failure potential. Stake a tree for a year or less to prevent dependence on the anchoring system. Following a high wind event/ tornado, consult with an ISA-certified arborist, who can guide follow-up pruning, straightening and removal of injured plants.

Photo: John C. Fech

Typical marginal moisture loss symptoms. (Photo: John C. Fech)

Desiccation/leaf scorch

Desiccation occurs when leaf and stem tissues lose moisture faster than the roots can absorb it and move it throughout the plant. These tissues are part of the permanent structure of a shrub, tree, perennial or ground cover. It’s usually caused by ex- tended extreme winds and cold/hot temperatures.

Avoiding plants with a history of desiccation injury in the course’s general area is a good preventive step. Others include applying an antidesiccant spray to conifers at the onset of win- ter and every six weeks during winter, installing burlap screens around susceptible plant material and watering ornamentals thoroughly in late fall and early summer.

Recovery from symptoms is difficult and often takes a full growing season. Generally, light pruning to remove dried tissues is the only reliable solution. The desire to abundantly water, fertilize and provide other care only worsens the appearance, so it’s best to allow plants to recover, then resume normal maintenance.

Sunscald

Sunscald results from repeated heating and cooling of bark tis- sues during winter. It typically occurs on thin-barked trees on the south, west and southwest sides of trunks.

Photo: John C. Fech

You can almost use sunscald incidence as a “compass,” as it occurs on the southwest side of a tree trunk in most cases. (Photo: John C. Fech)

Prevent sunscald by identifying species prone to damage such as maple and honey locust and by installing white- or beige- colored covers to reduce the bark’s warming. Working with a botanic garden, landscape designer/architect or university Extension horticulturist to choose trees not historically affected by sunscald is the best long-term approach.


John C. Fech is a horticulturalist with the University of Nebraska-Lincoln and a certified arborist with the International Society of Arboriculture.



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