Timely Tips for Backyard Gardeners
November 2, 2012
A weekly publication for Backyard Gardeners by
Ohio State University Extension
Preparation Against Winter Rabbit Damage to Plants
The eastern cottontail rabbit can be responsible for a considerable amount of damage no matter the season. In the spring they are feasting on greening vegetation such as clover, herbs, and flowering plants, leaving plenty of time for crops to ripen (fruits, vegetables, legumes), which are preferred summer foods. Once fall and winter roll around, rabbits will turn their attention to woody plants for sustenance. They will eat the bark, buds, stems, and tender twigs of a variety of shrubs, vines, and young trees.
Winter damage by rabbits is fairly easy to identify. Older woody growth will have evidence of gnawing, with marks from the rabbit's two front incisors usually evident. Twigs, vines, and stems will be neatly clipped off at a characteristic 45 degree angle. Round droppings in the area can also be used to identify rabbit damage. Keep in mind that rabbits are light enough to traverse on top of snow cover. Once the snow melts, the damage can be deceiving as it will appear to be much higher than a rabbit can reach. In places where snow drifts can reach 4 - 5' high, it's not uncommon to see rabbit damage to woody stems reaching that height.
Protect your woody plants this winter by surrounding them with a protective cylinder of hardware cloth or chicken wire. This barrier between your plant and hungry rabbits should be as tall as a rabbit's reach (about 2') while standing on the expected snow depth (perhaps another foot depending on where you live in Ohio). A mesh size of 1/4" is ideal but can be more expensive than large mesh sizes. Leave enough space between the plant and cylinder to prevent a rabbit from reaching tasty twigs through the wire if you use mesh larger than 1/4". A dome or cage of chicken wire or hardware cloth can also be used to protect your early blooming flowers in the spring. Creating a barrier between the plants and rabbits is often a successful tool against rabbit damage throughout the year if other attempts, such as repellents, have failed. For more information on managing rabbit damage visit the Internet Center for Wildlife Damage Management at: http://www.icwdm.org .
Watering and Mulching Newly Planted Trees and Shrubs
Water plants, especially evergreens, before the ground freezes. Excessive dry soils cause the death of small roots and reduce a tree’s capacity to absorb water, even after the soil is re-moistened. The resulting drought stress increases a tree’s susceptibility to certain diseases and insects. Precious energy reserves must be used to replace the lost roots. Keep your trees and shrubs adequately watered by following the guidelines listed below.
CHECKING SOIL MOISTURE
There is no way to look at the soil from above and tell how much moisture is in it. The only way to be sure of how much moisture is in the soil is to probe or dig. A trowel, metal rod, or soil sampling tool can be used. Low-cost soil moisture meters are not very accurate.
NEWLY PLANTED TREES
Proper watering is the single most important maintenance factor in the care of transplanted trees. Too much or too little water can result in tree injury. More trees are killed by too much water than by too little. Newly planted trees and shrubs may need to be watered regularly for 2-3 years until their root systems become established. Large trees may take longer.
For the first few months of the growing season after a tree is planted, the tree draws most of its moisture from the root ball. The root ball can dry out in only a day or two, while surrounding soil remains moist. To water the root ball and surrounding area, by let the hose run slowly at the base of the tree or use a root-watering needle under low pressure for 5-10 minutes.
The top 8-12 inches of soil should be kept moist around trees during periods of drought,
at least as far as the branches spread (drip line). It is impossible to give a formula on how much or how often to water a tree to keep the soil moist 8-12 inches deep. The amount of water required will vary with local site conditions, but without adequate rainfall, established trees may need to be watered as often as every 10-14 days. Don’t wait until your plants show signs of stress, such as wilting or yellowing.
Remember, you are not watering plants you are watering their roots. If the ground is level, simply let an open hose run on the ground and move it around occasionally to get good distribution.
If the ground slopes a little, water may easily run off the surface, and a sprinkler or soaker hose would distribute the water more slowly. If the ground slopes severely, a root-watering needle may be necessary. Insert the needle no more than 6 inches into the ground, and move it around frequently since it moistens a small area around the insertion point. No matter which watering method is chosen, it is important that you don’t saturate the trunk and that you keep the top 8-12 inches of soil evenly moist throughout dry periods.
BENEFITS OF MULCH
Provides an insulation layer. Mulched soils are warmer in winter and cooler in summer
than bare soils. Roots are protected from temperature extremes, creating less freezing and
thawing of the soil in winter, which can heave and injure plants.
Protect trunks of young, thin-barked trees, such as ash, maples, and lindens, from winter sunscald by wrapping trunks with a commercial tree wrap. The frequency and severity of winter damage is determined by a number of factors, including the plant species or cultivar involved, the location and conditions under which the plant is grown, and the exact timing of weather extremes during the dormant period. Contrary to popular belief, plant damage is not generally caused by an unusually cold winter. Low temperature injury is more often associated with extreme temperature fluctuation than with prolonged cold weather.
Acclimation to temperatures much below freezing results from exposure to slowly falling
temperatures and other factors. Plants that are dormant but not fully acclimated can be stressed or injured by a sudden, hard freeze. Rapid or extensive drops in temperature following mild autumn weather cause injury to woody plants. Extended periods of mild winter weather can de-acclimate plants, again making them vulnerable to injury from rapid temperature drops.
Some species or cultivars of trees and shrubs are injured if temperatures fall below a minimum tolerance level. Plants most likely to suffer winter injury are those that are marginally hardy for the area or those already weakened by previous stress.
Flower buds are often the most susceptible. If plants with marginal hardiness are used, they should be planted in protected sites, such as courtyards or sheltered areas. In general, low temperatures are much less damaging than rapid and extensive variations in temperature.
The Effects of Rain Soaked Soils on Plants
The effects of this week’s ‘Super Storm’ spilled over into Ohio and dumped a several inches of rain in many parts of the state, leaving some soils saturated with water.
To the extreme, very heavy rainfall followed by flooding can not only cause tremendous damage to buildings and homes, but also can kill woody and herbaceous plants, while other plants remain unaffected. The question is often raised, “How long can plants tolerate their roots being submerged?
It would depend on the time of year the flood event occurs, duration of the flood event, species sensitivity to flooding, and type of soil the plants are growing in. Dormant plants are more tolerant than actively growing plants to flooding. Most plants can tolerate a couple of days of flooding during the growing season.
Fortunately, most plants in this region are either dormant or well on their way to becoming dormant and the flooding was light in most areas, thus it is likely that damage to most plants will be minimal.
Established, healthy trees and shrubs will be more tolerant to flooding than very old trees, stressed trees, or young trees and seedlings of the same species. There are plants that can recover from flooding injury in as little as one growing season while others do not recover at all. However, these stressed trees are more susceptible to secondary organisms such as cankers fungi and wood boring insects. Trees that had a substantial amount of root injury and death are more subject to wind throw and should be monitored closely or removed entirely.
Another thing to be concerned about is the deposition of excess soil and rocks over tree roots following floodwater recession. Excess soil greater than 3” may impede oxygen transport from the atmosphere to tree and shrub roots, especially on smaller growing plants. This excess sediment should be removed after the water recedes. In contrast, tree roots may also become exposed due to soil erosion following flooding. These roots should be covered with soil to prevent drying out and damage of exposed roots. Improving drainage and aeration is critical to prevent future root injury. Finally, tree fertilization is not a cure for root injury and can make the problem worse.
(Source: The Effects of Flooding on Plants and Woody Plants Tolerant to Wet Soil, Jull, Laura G., UW Extension)
Pine Trees Dropping Needles Always Causes Concern
Pines don¹t keep their needles for ever, even though we call them evergreens. The older needles eventually fall off. White pines drop their two-year-old needles. Some years this is quite noticeable and others, you don¹t even see it.
People tend to worry about pines losing needles and rightly so. We have trouble with pines and other conifers in this area because of our clay soils. If the plants get additional stresses, such as being planted too deep or planted in a wet area, or lack of moisture during the summer months, they begin to decline.
You can differentiate inner needle yellowing from decline or other problems by taking a close look at the plant. If the yellowing or discoloration is on the older, inner needles, and all of them are doing it in a fairly even pattern, then it¹s normal. You will also see needles covering the ground around the inside of the canopy.