Some downtown areas of Houston were knee-deep in water, and some highways were shut down as a result of flooding from as much as 10 feet of water. In fact, some parts of Houston and just west of the city possibly received a Texas record of 50 inches of rain. Since making initial landfall as a Category 4 hurricane in southeastern Texas, Harvey dumped an estimated total of 20 trillion gallons of rain on the Houston area.
This was truly catastrophic to homes, vehicles and people. And, as the flooding recedes, you might be wondering what this excess and longer-standing water is also doing to your commercial landscape trees and plants. Here is some insight into what standing water and flooding does to plants and what we can do to help.
Unfortunately, there is nothing you can do to change the weather. While many landscape plants and trees can survive short periods of flooding, extended periods of standing water can often be detrimental. Flooding results in poor soil aeration because the supply of oxygen to flooded soil is severely limited.
And oxygen is one of the most important environmental factors that trigger growth inhibition and injury in flooded plants. Flooding of soils also increases the pH of acidic soils and decreases the pH of alkaline soils. Organic matter, which is beneficial to soils, also slows down its rate of decomposition when flooded. To add to that, high concentrations of ethanol and hydrogen sulfide are produced in waterlogged soils, which can be damaging to root systems. Soil can also be washed away around the base of trees and plants in a flood, exposing roots.
This can lead to plant stress. Shopping with the RHS. RHS Christmas gifts. Help us achieve our goals Make a donation. Join the RHS today and support our charity Join now. Save to My scrapbook. Quick facts. Common name Waterlogged or badly drained soil Plants affected All except a few tolerant ones Main causes Heavy rain combined with difficult soil conditions Main symptoms Yellow leaves, rotting roots, stunted plant growth Timing Winter and summer.
Jump to What is waterlogging and flooding? Symptoms Cause Control. What is waterlogging and flooding? Symptoms Symptoms of waterlogging are not easy to tell from other disorders but look for the following; The first symptoms appear on the leaves. This includes yellowing or decay between the veins, resulting in soft areas at the base or centre of the leaf.
There may be dark areas along the midrib, and areas within the leaf go brown, especially on evergreen leaves The plant may also look like it is short of water, even wilting A root sample will show blue-black roots, a typical sign of waterlogging that may be accompanied by a sour, rotting smell.
Roots may rot away completely, with few remaining. Damaged roots will be blackened and the bark may peel away Shoots may die back due to a lack of moisture the roots cannot supply water to the leaves and bark peels off the shoots easily Herbaceous plants may fail to sprout in spring, or leaves may open and then die Plants may be stunted, or even die Some plants suffer from a condition called oedema Some of the symptoms are easily confused with water stress too little water.
Cause Excess water causes problems for plants in a number of ways; Waterlogging limits oxygen supply to the roots and prevents carbon dioxide from diffusing away. Root function is reduced or stops and the roots start to die off, allowing the invasion of rots and decay organisms. This has a subsequent effect on the visible parts of the plant, as the leaves and stems are unable to obtain enough water and nutrients In cold, winter soils, roots and soil microorganisms respire little, so waterlogging is much less damaging than during warm seasons, when roots respire freely and demand more oxygen.
Few plants can survive summer waterlogging, unless they have special roots adapted to such conditions. Willows and marginal aquatic plants such as flag irises are examples of these Waterlogged soils may be compacted or have a naturally dense texture lacking drainage channels. This means that the soil remains wet after rain Hard landscaping does not allow rainfall to drain into the soil below. If you hard landscape part of your garden, more surface runoff has to be absorbed by a smaller area of soil which risks waterlogging.
Control Short term Where did the excess water come from? Heavy rain, groundwater flooding or from overflowing drains? Contact your water company if you believe it has come from overflowing drains that are outside of your garden After flooding, wash down hard surfaces and collect up debris to prevent drains blocking, soil surfaces being covered, and pollutants or contaminants lingering in the garden. Pin oak Quercus palustris can handle sodic conditions much better than red oak Q.
Eastern cottonwood Populus deltoides is another tree that can hold its water. Black tupelo, also called black or sour gum Nyssa sylvatica is fine with a couple weeks of water-soaked roots. Willows Salix spp. Hickories Carya spp. Symptoms of flood stress include chlorotic, wilting, undersize, or curling leaves, a sparse crown, early fall color as compared to others of its species , and branch-tip dieback.
Depending on all the factors discussed above, such symptoms may occur the first season, or they may take several years to manifest. When the time comes to think about the trees, one of the more important ways you can help is to do no harm — a very important point!
Do not park, drive, or stage materials within the root zone two times the branch length. Consider hiring an ISA Certified Arborist to assess your tree s and to also potentially aerate the root zone through pneumatic soil fracturing, vertical mulching, or other treatments.
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