While most types of trees thrive when their roots can occasionally access water, there are some that love having wet feet all throughout the year. These trees can withstand being rooted in waterlogged soil. They are thus perfect for stabilizing the substrate in rain gardens, minimizing erosion along lake and pond shorelines, and for adding complexity and color to permanently damp spots.
One would think that the adjective ‘water-loving’ is applicable to virtually all trees. Despite their reliance on water to survive, some tree species may rot in stagnant conditions. These may cause the substrate to be densely packed and dangerously anoxic.
Water-loving trees have developed the ability to expand their roots in oxygen-poor conditions. As they grow, they help soak up excess water and loosen the substrate, creating improved conditions for plants, fungi, and many wild animals that live in the soil.
Some of the most well-adapted trees are those that dominate swamps, rainforests, and coastal areas. These have root systems that are truly unique. With their fascinating and seemingly otherworldly adaptations, these trees are so thirsty for water that their healthiest specimens may drain what were once small, natural pools. A well-informed selection of flood-tolerant trees can even convert stagnant “dead zones” into productive systems.
1) Water tupelo (Nyssa aquatica)
Also known as sourgum, wild olive, and cotton gum, the water tupelo is a large, moisture-loving tree that can grow to an impressive height of 115 feet (35 meters). This phenomenal plant is known for shaping the ecological structure of many wetlands and swampy regions throughout its native range. It can survive in thoroughly flooded areas due to many structural adaptations. Deep, stagnant water rarely threatens its survival.
The water tupelo is best distinguished by a swollen base, which often remains wholly or partly submerged throughout periods of rainfall. The base smoothly tapers into a lengthy and mostly branchless tree trunk. The canopy gives this species fantastic ornamental value in the fall, when its leaves turn yellow. In spring, flowers bloom as new leaves begin to appear.
This species often occurs in dense and pure stands. One of the most flood-tolerant trees in all of North America, it has many industrial and ecological benefits. Its sturdy wood can be used in the production of commercial timber. In the wild, waterfowl, insects, and small mammals may rely on its fruits and leaves to survive.
2) Bald cypress (Taxodium distichum)
The predominant species in what is now known as ‘cypress swamps’, the bald cypress is a deciduous conifer with the capacity to bring structure and new life to flooded areas. Long-lived and slow-growing, this ecologically important tree is found in both old and new swamp stands. Some of the oldest stands have trees that are thousands of years old!
Bald cypress seeds are carried to other permanently flooded areas by streams and wild animals. These can survive underwater for up to 30 months, though they will only germinate on moist and exposed substrates. Their seedlings can grow quite quickly, able to keep their crowns above the water’s surface during the first year of growth. Those that are exposed to sufficient sunlight slowly begin to produce some of this plant’s most unique adaptations, which include its ‘cypress knees’. Researchers suggest that these structures aid in either nutrient acquisition or structural support.
Cypress trees are able to tolerate a wide range of soil types, pH levels, and water salinities. They have truly evolved to face some of the harshest conditions for plant survival. In permanently waterlogged regions, they form essential microhabitats and produce food to sustain wildlife. Their stands are often associated with water tupelo.
3) Swamp cottonwood (Populus heterophylla)
A member of the Salicaceae or willow family, the swamp cottonwood favors ambient conditions in bottomland forests, where rivers and streams may occasionally flood their root systems. It is considered a large tree as it can grow to about 70 – 90 feet (21 – 27 meters) tall on average. In optimal conditions, its trunk can spread to a diameter of 3 feet (1 meter). Heavy clay substrates, particularly those along the shoreline or edges of swamps, are typically preferred.
Though the swamp cottonwood does not have commercial value, it has ethnobotanical uses. Its wood can be used to produce paper pulp and materials for natural baskets and crates. It is far more valuable to wildlife as its young saplings and fruits serve as nutrient-rich food sources. The fruits come in the form of green capsules and develop within the tree’s white catkins.
Though the swamp cottonwood can grow quite quickly, it has a relatively short lifespan. Even in optimal conditions, this tree hardly lives for more than a century. Nonetheless, it is able to produce seeds after just 10 years of growth. The seeds, which require ample moisture to germinate, remain viable for just a couple of weeks.
4) Red maple (Acer rubrum)
One of the most abundant trees in the US, the red maple is known for being a hardy species. It is highly adaptable and can thus tolerate a markedly wide range of ambient and substrate conditions. This ecologically important tree, with both ornamental and industrial uses, tends to have subtle morphological variations throughout its native range. Those grown in open areas have trunks that can measure as much as 60 inches (1.5 meters) wide.
A deciduous species, the red maple has oppositely-arranged leaves with distinctly serrated margins. Each leaf, which starts off as bright green in spring, can have up to 5 lobes. Leaf color gradually deepens toward fall, during which the foliage becomes a dazzling display of orange to red hues. Fruits develop and mature even before the leaves are fully grown, so seeds become released into the wild as early as late spring.
Although A. rubrum may occasionally be found growing in dry sites, it has a preference for consistently moist substrates. Its root system is able to develop in different ways, with variations being a function of the availability of water. In wet areas, the tree is stabilized by an extensive lateral root system. This is capable of taking up significant amounts of water. In dry areas, the tap root becomes more prominent.
5) River birch (Betula nigra)
As suggested by its common name, B. nigra favors moist conditions along the shorelines of rivers and streams. It is also occasionally found in swamps and floodplains throughout its native range. Hardy to USDA zones 4 – 9, it thrives best in mild ambient conditions. If ample moisture is available, it can tolerate heat exposure quite well.
The river birch is frequently cultivated as a natural means of achieving erosion control and land reclamation in wetlands. It is classified as flood-tolerant because its roots can survive up to two seasons in total submersion. While it does persist through floods, however, drier periods are necessary for optimal growth.
The seeds of river birch require a generous amount of moisture to successfully germinate. Due to their water-loving nature, they grow into seedlings that dominate pioneering plant communities along the alluvia of channels, streams, and rivers. Young trees tend to grow vigorously, sprouting fresh stumps that eventually develop into beautiful trunks.
6) Weeping willow (Salix babylonica)
Known best for the gracefully arching appearance of its drooping twigs, the weeping willow has a rich cultural history. Traded countless times along the Silk Road, this attractive tree is a fixture in some extremely important and popular texts, such as the Book of Psalms. Unsurprisingly valued as an ornamental, it seems to carry an almost unbearable weight in the form of its cascading foliage.
The weeping willow is now fairly widespread throughout North America and Europe. In the wild, it tends to grow close to water bodies or in areas with consistently moist soil. In areas with seasonal floods, the root systems of mature specimens can tolerate brief periods of full submersion. Nonetheless, this species does require stretches of dryness to rapidly grow.
Compared to those of regular perennials, the roots of weeping willow have the capacity to absorb a considerable amount of water. Dense stands of this species can actually drain small water features. Full sun exposure should help this species adjust to prolonged periods of wetness. Avoid planting this tree close to underground water lines, as its extensive roots can spread aggressively.
7) Sweetbay magnolia (Magnolia virginiana)
The perfect flowering tree for adding foliar texture and ample height to rain gardens, the sweetbay magnolia tolerates poor substrates and wet conditions. This species is also known as laurel magnolia, swamp bay, and beaver tree. Compared to those of its close relatives, which may struggle to survive in wet substrates, its root system can thrive in bogs and close to ponds, lakes, and streams.
This evergreen to semi-evergreen tree should be exposed to full or partial sunlight and ample ventilation. Hardy to USDA zones 5 – 10, its capacity for growth is influenced by climate conditions. Towards the north of its range, it may grow as an oversized shrub, reaching a full height of just 15 – 20 feet (4.6 – 6 meters) tall. In warmer, southern regions, it can grow to about 60 feet (18 meters) tall.
M. virginiana blooms appear from May to June. These are distinguished by a velvety set of cream-colored petals that curl upward to create a cup-like shape. With a scent likened to that of fresh lemons, they open and close with the rise and fall of the sun. Eventually, this tree produces bright red seeds to attract fruit-eating birds.
8) Water ash (Fraxinus caroliniana)
Also known as the swamp ash and pop ash, this subtropical, deciduous tree grows to a relatively short maximum height of 40 feet (12 meters). On average, it measures just 25 feet (7.6 meters) tall and may thus be cultivated as an oversized shrub. With a notably slender diameter of 6 – 8 inches (15 – 20 cm), its trunk is more enlarged towards the base and quite narrow at the crown.
Despite its short height, this tree is known for being long-lived. It favors conditions in wetland regions with deep swamps. Its root system and shoot base are able to tolerate being submerged for 1 – 2 seasons (usually winter to spring) each year.
An important part of the understory throughout its native range, the water ash thrives under partial or dappled sunlight and when it is planted in slightly acidic, moist to wet soil. Due to its tolerance for periodically waterlogged substrates, it can be planted in rain gardens, along the margins of ponds, or in areas with problematic, boggy conditions. If you do intend to grow it, keep an eye out for the emerald ash borer. This exotic beetle has begun to threaten wild stands of this species.
9) Mangrove fan palm (Licuala spinosa)
If you’re in need of an attractive ornamental palm that can add charm and attractiveness to the edges of your water features, look no further! The mangrove fan palm prospers in wet areas and can tolerate being exposed to both fresh and salt water. While it does grow best in the tropics, it is a decent candidate for cultivation in regions with mild temperate to subtropical conditions. It is more cold-hardy than most of its close cousins.
The mangrove fan palm has a rapid growth rate and can quickly produce masses of eye-catching and bright-green leaves. The leaves, which are made of multiple leaflets, fan out in the costapalmate orientation that is typical of many Licuala palms. Collectively, the leaflets thus create a rounded shape. For protection, the plant has evolved to produce spines along the length of its petioles.
This palm tree is ideal for oriental-themed water gardens requiring shade and vertical texture. It may be more difficult to acquire compared to other palms, but it is worth searching for if you require a tropical tree that can survive brief floods.
10) Black alder (Alnus glutinosa)
If this list didn’t have at least one highly invasive species, it wouldn’t be doing justice to the hardiness and adaptability of some of the most water-loving trees! The black alder, now classified as a pest plant in many parts of the US, is one such tree that is remarkably tolerant of unfavorable conditions. Due to its capacity for rapid growth and its ease of establishment in poor-quality soils, it has become a pioneer species in disturbed and vacant lands. As long as there is accessible water, it can flourish.
In fact, water is a major vector of dispersal for seeds of the invasive black alder. When these are transported into new localities with occupiable and regularly moistened substrates, they can germinate even where there is minimal light. The saplings then grow quickly enough to alter the local ecology of their new habitats. They eventually produce dense networks of expansive root systems. Interestingly, even the felled logs and fallen branches of this species can produce roots in swampy areas.
11) White cedar (Thuja occidentalis)
Commonly cultivated as an ornamental tree, the white cedar or ‘arborvitae’ is an attractive member of the cypress family (Cupressaceae). As it grows to a moderate height of just 49 feet (15 meters), it is often considered a small tree. Its modest size makes it less demanding in terms of maintenance. This is partly what makes it favorable as a garden or landscape tree.
In optimal conditions, white cedar produces dense sprays of highly textural foliage. The leaves, composed of seemingly scale-like leaflets, may have a fan-like shape. The entire plant, which produces leafy branches from the base of the trunk all the way to the young tip, may appear conical and stately. This evergreen tree effectively adds color to the garden through fall and winter. Its reddish-brown cones can remain on the tree until final frosts occur.
T. occidentalis grows best in swampy conditions, where its root systems can easily access water. In spite of its slow growth rate, many other plants may struggle to compete with its capacity to dominate these moist habitats. In rich-conifer swamps, it is usually associated with other water-loving trees like the swamp tupelo and bald cypress.
12) Sweet gum (Liquidambar styraciflua)
Another popular ornamental plant, the sweet gum tree is remarkably eye-catching due to its maple-like foliage. It is a deciduous species that produces five-pointed, dark-green leaves in spring. These eventually become orange to red in the fall, just before they fall off to mark the onset of winter. In warmer regions, however, sweet gum trees may be evergreen.
This species is one of the most common hardwood trees in the lowland regions of the southeastern US. It grows best in acidic, loamy, or clay substrates. As its roots are fairly tolerant of poor drainage conditions, it can be cultivated in moist to wet soils. Note that it is more likely to survive through periodic floods if it receives full sun exposure.
The sweet gum tree is a stunning plant to grow close to the shorelines of ponds and lakes. Its highly textural appearance can soften the edges of these water features, especially if its canopy is close enough to be reflected onto the water’s surface. In the wild, it typically occurs alongside sweetbay magnolia trees, which likewise favor moist conditions.
