by Lis Friemoth
Weather woes
Water, wind, temps can cause damage
Plant health can present symptoms that may fool an observer, especially if they’re not watched over time. Patient monitoring of external changes, consideration of weather conditions, soil moisture levels and fluctuations in insect populations will result in a clearer picture of health-related issues.
The top health concern on my list is damage resulting from environmental pressures. Damage symptoms may mimic fungal and bacterial infections. And unfortunately, many environmental stresses can happen simultaneously in one landscape, making it even more difficult to pinpoint the cause. The damage can develop and mature so rapidly that you may not even realize you have issues until the damage has run its course.
One of the first environmental conditions to look at is the level of long- and short-term soil moisture. Although there have been intermittent deluges throughout the early growing season, plant needs must be evaluated and compensated for on a regular basis. This is especially true, since we’ve had five years of drought-like conditions (some years more severe than others) and the long-term effects are starting to show around the area.
When we talk about long-term moisture, we are looking at the deeper levels within the soil profile — those that provide the necessary elements for solid deep-rooted structuring — and the areas that provide replenishment of soil moisture reserves. Every year that falls short in rainfall increases the deep-reserve deficit. With that deficit comes an inability by plants to maintain root health at deep levels. The result is that roots must search closer to the soil level to find moisture, creating a top-heavy, shallow and much less stable support structure.
Without a consistent source of moisture within the shallow layer, the top eight to 12 inches, the fine-feeder roots will dry up. When this occurs, plant energy will be expended on regenerating the root structure, rather than on providing for plant growth and maintenance. All shallow-rooted annual, perennial, tree and shrub plant material relies mainly on that short-term moisture to grow, survive and thrive, and will decline quickly when moisture is inadequate. The leaf cells will close off to prevent system loss through transpiration, leaves wilt, and the plants are unable to properly process food, water, and nutrition.
This creates system stress which then invites disease and insect infestations. Symptoms typically observed with inadequate levels of either short or long-term soil moisture include failure to leaf, smaller leaf size, leaf and entire plant wilting, necrosis of leaf tissue, failure to hold leaves throughout the season, failure to drop leaves at the end of the season, overall decline in vigor and excessive seed/fruit production.
Wind can also create extremely stressful situations for plant material. Early in the season, when leaves are tender and just expanding, warm or cold winds can do a couple of things to the leaves. It can pull all available moisture out of the leaf and stem tissue or just simply freeze or fry the tissue. If soil moisture levels are adequate, the plants may be able to replenish system reserves before permanent long-term damage is done. But this year, our plants were subjected to cold, snow and ice after a warm stretch, followed by very high temperatures, extremely fierce winds, all with the added bonus of low levels of soil moisture.
Under “normal” growing conditions, healthy trees, shrubs and perennials can refoliate, which is what happened earlier this season. But just as the second set of leaves were emerging, we got hit with another round of hot, intense winds. If soil moisture levels are adequate for the next month or so, the plant material has a chance to recoup losses and possibly do OK. If soil moisture declines, the plants will be in tough shape for the rest of the season.
If the damage occurs at the leaf edges, they will look tattered and a bit beat up; the damaged tissue will turn dark in color, and after it dries up, will fall off, leaving the leaf looking rather chewed along the margins. If the leaf tissue between the veins suffers the most damage (this happens if the winds hit as the leaf is just expanding) that internally located tissue will dry up and fall off — again, giving it the appearance of being chewed. When branches are affected, leaves may emerge smaller in size or not at all, or you may see loss of some small or large branches.
Temperatures greatly impact the health of plant material. Some simply cannot handle heat; some cannot take the cold. In other instances, the extreme swings are a kind of roulette for plant life. When extreme temperature fluctuations occur early in the season, plants often do not have strong enough systems to withstand the same stresses that they can easily shrug off later on in the growth cycle.
Some of the symptoms of temperature damage include discoloration of leaf tissue, branch dieback, unsuccessful fruit or seed production, tissue necrosis and root death.
— Lis Friemoth is a horticulture diagnostician. Contact her at (262) 745-2904, P.O. Box 58, Springfield, WI 53176, visit online at www.thegardenhoe.com or e-mail her at gardenhoe@tds.net. Listen to Liz from 9 a.m. to 10 a.m. every third Saturday on WISN AM1130 radio. |
