Flood-Tolerant Trees

Given the global climate disruption of the current era, floods are more common than ever … and happen at seasons when they never occurred in the past. While I would hope your home is built on high ground, far from any raging, flood-engorged river or overflowing lake, part of your property might not be. 

The nearby lake or river is likely bordered by trees, as they’re often used to help prevent erosion and, besides, it’s not always possible to do any kind of intensive gardening on a sloping riverside. Plus, trees simply look good near any body of water. 

So, how does flooding affect them?

Not Good for Roots

Being underwater for extended periods is not good for tree roots. They need oxygen which they usually get from air stored in tiny spaces between soil particles, but when the soil is flooded, these air spaces fill with water and out goes the oxygen. Roots then are placed in an anaerobic condition: they can’t get the oxygen they need for respiration. Roots soaking constantly in water can lead to numerous problems, like a buildup of toxic compounds within the tree, reduced nutrient uptake, but especially root death. And too many dead rootlets can kill the tree.

Mother Nature has provided some trees with adaptations to flooding. Many can tolerate a week or so of flooding, especially when it occurs early in the spring while they’re dormant. Others, like cottonwoods (Populus deltoides and related species and hybrids), naturally grow on floodplains and can take months of flooding, often standing tall and perfectly green well into summer when spring floodwaters are slow to drain away.

Flood Tolerant Trees

Here are some examples of trees naturally adapted to flooding … and that you might want to consider planting in areas subject to water overflow. All are able to survive flooding or saturated soils for 30 to 120 consecutive days during the growing season.

• Alders (Alnus spp.)—most species
• American larch (Larix laricina)
• Baldcypress or swamp cypress (Taxodium distichum)
• Balsam poplar (Populus balsamifera)
• Bird cherry (Prunus padus)
• Black poplar (Populus nigra)
• Black spruce (Picea mariana)
• Catalpa (Catalpa spp.)
• Cottonwoods (Populus deltoides and others)
• Dawn redwood (Metasequoia glyptostroboides)
• Green ash (Fraxinus pennsylvanica)
• Hackberries (Celtis spp.)
• Manitoba maple or boxelder (Acer negundo)
• Overcup oak (Quercus lyrata)
• Pecan (Carya illinoensis)
• Persimmon (Diospyros virginiana)
• Red maple (Acer rubrum)
• River birch (Betula nigra)
• Silver fir (Abies alba)
• Silver maple (Acer saccharinum)
• Sweetgum (Liquidambar styraciflua)
• Sycamores (Platanus spp.)
• Water hickory (Carya aquatica)
• Water oak (Quercus nigra)
• Water tupelo (Nyssa aquatica)
• Willows (Salix spp.)—most species
• Winged elm (Ulmus alata)

Intermediate Flood-Tolerant Species

These trees will tolerate flooding for up to 30 days during the active growing season. Only plant them near a body of water if any flooding is likely to be of short duration.

• American elm (Ulmus americanus)
• American holly (Ilex opaca)
• Arborvitae (Thuja spp.)
• Balsam fir (Abies balsamea)
• Black walnut (Juglans nigra)
• Buckeyes (Aesculus spp.)
• Buckthorn (Rhamnus cathartica)
• Bur oak (Quercus macrocarpa)
• Chestnuts (Castanea sativa and others)
• Common aspen (Populus tremula)
• English oak (Quercus robur)
• European ash (Fraxinus excelsior)
• Field elm (Ulmus minor)
• Field maple (Acer campestre)
• Fringetree (Chionanthus spp.)
• Honeylocust (Gleditsia triacanthos)
• Hophornbeams (Ostrya spp.)
• Horse chestnuts (Aesculus spp.)
• Lacebark elm (Ulmus parvifolia)
• Littleleaf linden (Tilia cordata)
• Loblolly pine (Pinus taeda)
• Paper birch (Betula papyrifera)
• Pin oak (Quercus palustris)
• Plums (Prunus spp.)
• Quaking aspen (Populus tremuloides)
• Serviceberry (Amelanchier spp.)
• Shellbark hickory (Carya laciniosa)
• Slippery elm (Ulmus rubra)
• Smoketree (Cotinus spp.)
• Sugar maple (Acer saccharum)
• Swamp chestnut oak (Quercus michauxii)
• Swamp white oak (Quercus bicolor)
• Tupelo or black gum (Nyssa sylvatica)
• White ash (Fraxinus americana)
• White poplar (Populus alba)
• Willow oak (Quercus phellos)
• Yellow birch (Betula alleghaniensis)

Flood-Intolerant Trees

The following trees, largely ones normally found in upland situations in the wild, can be damaged by only a few days of constant soaking during the growing season. Even while dormant, much more than a week of saturation can kill them outright. 

Avoid planting the following trees in areas where flooding is even a possibility. 

• American basswood (Tilia americana)
• Amur maackia (Maackia amurensis)
• Amur maple (Acer ginnala)
• Apple (Malus spp.)
• Beeches (Fagus spp.)
• Bigtooth aspen (Populus grandidentata)
• Black locust (Robinia pseudacacia)
• Black oak (Quercus velutina)
• Butternut (Juglans cinerea)
• Charms (Carpinus spp.)
• Cherries (Prunus spp., except P. padus)
• Common holly (Ilex aquifolium)
• Cork tree (Phellodendron amurense)
• Crabapples (Malus spp.)
• Crape-myrtle (Lagerstroemia indica)
• Douglas fir (Pseudotsuga menziesii)
• Downy oak (Quercus pubescens)
• European larch (Larix decidua)
• Flowering dogwood (Cornus florida)
• Ginkgo (Ginkgo biloba)
• Golden raintree (Koelreuteria paniculata)
• Hawthorn (Crataegus spp.)
• Hemlock (Tsuga spp.)
• Japanese lilac (Syringa reticulata)
• Japanese maple (Acer palmatum)
• Junipers (Juniperus spp.)
• Kentucky coffeetree (Gymnocladus dioicus)
• Kousa dogwood (Cornus kousa)
• Large-leaved lime (Tilia platyphyllos)
• Magnolias (Magnolia spp.)
• Mountain ash or rowantree (Sorbus spp.)
• Norway maple (Acer platanoides)
• Paperbark maple (Acer griseum)
• Pears (Pyrus spp.)
• Persian walnut (Juglans regia)
• Pignut hickory (Carya glabra)
• Pines (Pinus spp., except P. tieda)
• Red oak (Quercus rubra)
• Redbuds (Cercis spp.)
• Rock elm (Ulmus thomasii)
• Russian olive (Elaeagnus angustifolia)
• Sassafras (Sassafras albidum)
• Scarlet oak (Quercus coccineus)
• Sessile oak (Quercus petraea)
• Shagbark hickory (Carya ovata)
• Siberian elm (Ulmus pumila)
• Silver birch (Betula pendula)
• Silver linden (Tilia tomentosa)
• Silverbell (Halesia carolina)
• Sourwood (Oxydendrum arboretum)
• Spruces (Picea spp., except P. mariana)
• Staghorn sumac (Rhus typhina)
• Sycomore maple (Acer pseudoplatanus)
• Tulip tree (Liriodendron tulipifera)
• White oak (Quercus alba)
• Wych elm (Ulmus glabra)
• Yellowwood (Cladastris lutea)
• Yews (Taxus spp.)

What to Do After Flooding?

There’s not much you can do after a flooding incident but wait. If healthy new growth appears, all is probably fine. If new growth is weak or chlorotic and the tree doesn’t recover within a year, it would be worthwhile having it assessed by a professional arborist.