Effects of Flooding on Woody Landscape Plants (A3871)
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A3871 ffects of flooding on E woody landscape plants LAURAG.JULL The question often asked fol- Symptoms of plants experiencing Will my plants survive? lowing a flood is, “How long will flooding stress include yellowing or my plants survive with their roots browning of leaves, leaves curling The likelihood of woody land- under water?” The answer depends and pointing downward, leaf wilt scape plants surviving a flood on a variety of factors including time and drop, reduced size of new leaves, depends on a variety of factors: of year, how long the roots remain early fall color, branch dieback, for- I Time of year. submerged, soil type, plant species, mation of sprouts along stems or Dormant plants and age and health of the plant. The trunk, and, in extreme cases, gradual are more tolerant of flooding effect of each factor is described at plant decline and death. than are actively growing right. Roots need oxygen for growth plants. Some plants can recover from and respiration, so the longer they’re I How long roots remain flooding injury in as little as one submerged, the more difficult it is for submerged. Most plants can growing season; others may never the roots—and plant—to survive. recover. Plants that survive a flood Trees that have suffered a substantial tolerate a few days of flooding should be given special care to help amount of root injury are prone to during the growing season. them recover. “windthrow” (being uprooted in Some can survive a week or Symptoms of heavy wind) and should be moni- more of standing water (some flood stress tored closely or removed. Trees that species can survive months of begin to lean severely should be standing water). Besides the obvious damage to removed as soon as possible. I Sensitivity of the species to submerged branches and foliage, few Stressed trees are more suscep- excess water. For sensitive plants can tolerate having their roots tible to secondary organisms such as tree and shrub species (listed in submerged for long periods of time. canker fungi and insects that bore (Refer to tables 1 and 2 for plants into phloem and wood. table 1), anything more than a likely to be injured by flooding and few days can start to cause those that can tolerate wet soils.) severe injury and death. I Soil type. Sandy soils drain much faster than predomi- nantly clay-based soils, which hold water and remain wet for longer periods. I Age and health of plant. Established, healthy trees and shrubs will be more tolerant of flooding than very old, stressed, or young plants of the same species. EFFECTSOFFLOODINGONWOODYLANDSCAPEPLANTS Why do plants die in I water-soaked soils? Even when standing water is not Remove any dead, damaged, or present, poorly drained soils can diseased branches. I Roots need oxygen for growth reduce plant growth and long-term Water plants thoroughly (1 inch and respiration. Flooding reduces the survival in the landscape due to low per week) during extended amount of oxygen in the soil, oxygen levels in the soil. droughts. impeding root respiration. As a result, Caring for flood- I Aerate the soil around the tree’s carbon dioxide, methane, hydrogen stressed plants roots using vertical or radial and nitrogen gas levels around the Immediate plant care needs mulching (should be performed roots increase sharply. The roots then by a professional arborist to suffocate and die. Toxic compounds, Once floodwaters have receded, inspect the soil around your plants. protect roots). such as ethanol and hydrogen sulfide, I can build up in saturated soils. As Flooding may have deposited signifi- Properly mulch trees. Spread root function becomes impaired, pho- cant amounts of new soil and rocks 2–4 inches of shredded bark (not tosynthesis in the leaves is inhibited over plant roots—or it may have wood chips) in a donut shape and growth slows or even stops. eroded soil, leaving roots exposed. If around the base of your plants, Excessively wet soils also favor more than 3 inches of debris has been keeping mulch away from the soil-borne root and crown rot organ- deposited, remove it to allow oxygen trunk and off any low-growing isms including Fusarium spp., movement from the atmosphere to branches. tree and shrub roots. Conversely, care- I Phytophthora spp., Pythium spp., and Do not fertilize trees and shrubs fully cover any exposed roots with Rhizoctonia solani. These organisms for at least a year following a flood soil back to the original depth to affect many species and prefer wet due to root injury. Nutrient uptake prevent drying or damage. soil conditions. Long-term plant care strategy is an energy-requiring process that will further stress the plant, espe- Plant health care is an important cially during times of flooding component to improve plant vigor (and drought). and further reduce plant decline. Table 1. Plants likely to be injured by flooding Scientific name Common name(s) Scientific name Common name(s) Acer platanoides Norway maple Ostrya virginiana American hophornbeam, ironwood Acer saccharum sugar maple Picea abies Norway spruce Aesculus spp. buckeyes, horsechestnuts Picea omorika Serbian spruce Betula papyrifera paper birch, canoe birch Picea pungens Colorado spruce Betula populifolia Whitespire Senior gray birch Pinus spp. pines ‘Whitespire Senior’ Prunus spp. cherries, plums, peaches, apricots Carya spp. hickories Quercus alba white oak Cercis canadensis eastern redbud Quercus muehlenbergii chinkapin oak Cladrastis kentukea American yellowwood Quercus robur English oak Cotoneaster spp. cotoneasters Quercus rubra northern red oak Crataegus phaenopyrum Washington hawthorn Rhododendron spp. rhododendrons Daphne spp. daphnes Robinia pseudoacacia black locust Euonymus spp. euonymus Sorbus spp. mountainashes Fagus spp. beeches Spiraea japonica Japanese spirea Juglans nigra black walnut Syringa spp. lilacs Juniperus spp. junipers Taxus spp. yews Ligustrum spp. privets Tilia spp. lindens Liriodendron tulipifera tuliptree, tulip-poplar Tsuga canadensis Canadian hemlock, Magnolia spp. magnolias eastern hemlock Malus spp. flowering crabapple Ulmus pumila Siberian elm Microbiota decussata Siberian cypress, Weigela spp. weigelas Russian-arborvitae Yucca spp. yuccas Morus alba white mulberry Table 2. Woody landscape plants able to tolerate wet conditions Scientific name Common name(s) Zone Notes Modifying the TREES—Deciduous landscape W Acer x freemanii Freeman maple 3b native hybrid Acer negundo boxelder 2b native, reseeds and sprouts readily W If water routinely stands in an Acer rubrum red maple 3b/4ba native, acid soils only W area following heavy rains, you may Acer saccharinum silver maple 3a native, reseeds and sprouts readily W Alnus glutinosa European black alder 4a invasive wish to consider improving drainage W and aeration, and replanting the area Betula nigra river birch 4a native, acid soils only Carpinus caroliniana musclewood, American 3b native, periodic flooding only with plants that are able to tolerate hornbeam, ironwood wet conditions. Catalpa speciosa northern catalpa 4a W Before making any changes, eval- Celtis occidentalis common hackberry 3b native Fraxinus mandshurica Manchurian ash 3 susceptible to EABb uate the drainage situation. Is your W Fraxinus nigra black ash 3a native, susceptible to EABb area permanently wet, somewhat wet, W Fraxinus pennsylvanica green ash 2a native, susceptible to EABb W or wet for only a few days at a time? Gleditsia triacanthos thornless honeylocust 4a native For areas that are permanently var. inermis Gymnocladus dioica Kentucky coffeetree 4a native, periodic flooding only wet, you may be best off planting W Larix laricina tamarack, American larch 2 native, acid soils only species that are tolerant of wet soils. W Liquidambar styraciflua sweet gum 5b Bottomland plants that naturally Maclura pomifera osage-orange, 4b female trees have very large, grow in lowland areas along river- Bois-D’arc messy fruit banks subject to fluctuating water Metasequoia dawn redwood 5b glyptostroboides tables are able to tolerate wet soils Nyssa sylvatica black gum, sour gum, 4b native, acid soils only better than upland species that grow tupelo Platanus x acerifolia London planetree 5b at higher elevations. Also, different W plants tolerate different degrees of Platanus occidentalis American sycamore, 4b native, disease prone American planetree W wetness. Woody species that can tol- Populus deltoides eastern cottonwood 3a native, reseeds readily, messy tree, erate wet soils are listed in table 2. disease prone In areas prone to staying wet for Quercus bicolor swamp white oak 4a native Quercus macrocarpa bur oak 3a native only a few days at a time, you can W Quercus palustris pin oak 4b acid soils only improve soil porosity before planting Quercus x schuettei swamp bur oak 4 native hybrid W by adding loose organic material, Salix ‘Golden Curls’ Golden Curls willow 4b W Salix lucida shining willow 2 native such as composted leaves, pine bark, W and peat moss. Salix matsudana corkscrew willow, 4b ‘Tortuosa’ curly willow W Other options for improving Salix nigra black willow 4a native, messy tree W drainage include planting on raised Salix x pendulina ‘Blanda’ Wisconsin weeping willow 4 messy tree W Salix pentandra laurel willow 2b beds or berms, and installing swales, W Salix ‘Prairie Cascade’ Prairie Cascade willow 3b messy tree waterways, and drain tiles to divert W excess water away from trees and Salix x sepulcralis golden weeping willow 4a messy tree var. chrysocoma W shrubs. Taxodium distichum baldcypress 4b W Resources Ulmus americana American elm 3a native, pest prone, plant only Dutch TREES—Evergreen (narrow-leaved) elm disease–resistant cultivars Ball, J. and D.F. Graper. 1996. What to Abies balsamea balsam fir 3a native, acid soils only do about flood-damaged trees? South W Chamaecyparis thyoides Atlantic white-cedar 4b shrub forms available Dakota State University Extension W Picea mariana black spruce 3a native in bogs, hard to grow, Extra publication, Brookings, SD. shrub forms available, acid soils Coder, K.D.