Water runoff, from heavy rain, floods, rising water levels, clogged sewers, or an endlessly leaking faucet can quickly turn a portion of your garden into muck. As stormwater makes its way into a swale or depression of ground where it can settle, it brings loose particles of sediments, leached nutrients, and potential contaminants. These can be detrimental to the water quality in gardens and farms and may cause severe damage to properties.
Plants that are averse to waterlogged soil can suffer due to storm runoff and quickly develop root rot. Fortunately, there are some water-loving greens that may help remove standing water. These can also be situated around a pond to help prevent runoff, whether from the pond itself or external sources, from spreading.
Many horticulturists use these plants in rain gardens, which slow down the flow of water and filter out toxins. The plants then help redistribute water by developing a complex underground system of moisture-loving roots. Runoff that results in standing water may be due to a design flaw in your garden, or perhaps you just happen to live at the foot of a hill. If the water remains stagnant and cannot be absorbed by the underlying substrates, it will eventually become a breeding ground for pests and pathogens.
While there are other methods of resolving runoff, such as grading and berm construction, these trees, shrubs, and herbs are a cost-effective and visually appealing way of improving drainage. Aim to use perennial species that are native to your area.
1) River birch (Betula nigra)
Known for growing close to the banks of rivers, in floodplains, and even in swamps, this birch tree is one of the few species in its family (Betulaceae) that thrive in warmer temperate regions. Ideally, this tree should be grown in USDA zones 4 – 9. It is a deciduous species that is largely distinguished by the paper-like scales of its trunk and its late spring fruits. Mature trees have deeply furrowed trunks and can measure up to 100 feet (30 meters) tall.
The river birch provides many ecological benefits due to its tolerance to flooding. Even its saplings can persist in floodplains as long as they receive full sun exposure. Older trees can aid in erosion control and can be planted in areas with acidic substrates. They can provide dappled shade to a garden while taking up excess moisture. They also have ornamental value due to their distinctive bark features. The cultivars ‘Heritage’ and ‘Dura heat’ are favored for their light to white-colored bark.
The uses of this tree extend into the industrial and pharmacological realms. While its wood can be harvested for use as furniture, its inner bark is a source of essential oils and can be exploited as survival food. Its oils have shown potential for use as a natural insecticide or antibiotic. Deer and waterfowl also favor the humble river birch as a food source.
2) Red maple (Acer rubrum)
Also known as the swamp maple, A. rubrum is one of the most commonplace trees in the US. Its widespread distribution is perhaps due to its tolerance for a wide range of conditions. It is often used as an ornamental species for fall interest due to its stark red foliage. The fruits and twigs are various shades of red too. The tree’s general features and coloration vary depending on the cultivar and habitat conditions.
The red maple can persist in swamps, making it an ideal species for rain gardens or swales. In the southern reaches of its natural range, it is largely restricted to swampy areas as it favors consistently moist soil. It can also tolerate a wide range of pH conditions and substrate types. Without a preference for directional exposure, it can be planted almost anywhere in the garden and can even survive in shaded zones.
From a young age, the tree has a capacity for root plasticity. This means that the type of roots it sends out is influenced by its environment. When grown in wet patches, young red maples tend to develop longer lateral roots to keep a firm grasp on the soil. The taproots, in contrast, remain short. The opposite has been observed in dry areas.
3) American cranberrybush (Viburnum trilobum)
Despite being called a cranberrybush, V. trilobum is not a cranberry tree. It is a deciduous shrub that produces cranberry-like fruits. They even taste remarkably like cranberries, which come into fruit during the same time of year. Luckily, the cranberrybush fruits are edible and are actually a rich source of vitamin C. They can even be made into a sauce to go with meaty dishes, just like cranberries.
In its native environment, V. trilobum favors moist substrates, such as those found along the margins of freshwater features. It requires persistent moisture to flourish but does appreciate proper drainage. With a growth rate of around 3 feet per annum, it can reach its mature height of 12 feet (3.6 meters) in just 4 years. A single shrub can even have a spread of about 10 feet (3 meters). If the swale in your garden is quite large, then this is the perfect plant for you!
A superb species for pollinators and wildlife, the cranberrybush provides stunning year-round interest. Its spring inflorescences appear as clusters of tiny, white-colored blooms which are surrounded by a circle of larger flowers. Berries begin to appear in fall, when the leaves turn purple to red. These are an important source of nourishment for birds in winter.
4) Common buttonbush (Cephalanthus occidentalis)
C. occidentalis can be cultivated as a shrub or a small tree. It favors consistently moist habitats, such as floodplains, riparian forests, and swamps in wetland regions. Its stands are also notable occupants of Florida’s Everglades, which form a tropical drainage basin. As it has evolved to thrive in these areas, it would undoubtedly play a crucial role in swales that tend to collect runoff. It can also be planted along slopes as its enlarged base can help control erosion.
The terminal inflorescences of buttonbush are its standout features. The flowers are densely arranged into a perfect sphere. They have a somewhat spiky appearance due to their tube-like corollas, which are topped with yellow stamens. When these are pollinated, they turn into sphere-like clusters of small nuts. These are a great source of nutrition for waterfowl.
The foliage of the common buttonbush is known for being toxic to livestock, though deer seem to be able to graze on it without consequence. It contains cephalanthin, a glycoside that can supposedly dissolve corpuscles in blood and induce a nasty string of toxic symptoms. This may not be the most ideal species to cultivate if pets or children frequently roam around your garden.
5) English hawthorn (Crataegus laevigata)
The European hawthorn can grow into a moderately-sized tree as it reaches an average height of about 26 feet (8 meters). It can also be cultivated as a large shrub, though pruning will have to be done frequently. Its multi-lobed leaflets form broad, dark green leaves. These are pleasantly contrasted by white to pale pink flowers in mid to late spring. Though the foliage is unremarkable in fall, dark red fruits may begin to appear.
Several cultivars of this species and some hybrids with C. monogyna have earned the RHS Award of Garden Merit. These include ‘Rosea Flore Pleno’, and ‘Paul’s Scarlet’, which have double pink to red-colored flowers. The blooms can seemingly occur throughout the crown of the tree, giving it spectacular color. As a plus, the fruits can persist into winter long after the last leaves have fallen. They look especially charming when dangling from snow-covered branches.
C. laevigata thrives in moist soil and is frequently planted in rain gardens. While its roots have a tolerance for moderately wet feet, its leaves require full sun exposure to flourish. This plant is recommended for brightly lit hedges that may occasionally be flooded with water runoff. Note that its fruits should not be consumed in large doses as they may cause digestive issues.
6) Blue flag iris (Iris versicolor)
A beloved pondside plant, Iris versicolor is a lovely species that never fails to spruce up the margins of water features. Its erect shoots, topped with vivid blooms in mid-spring to summer, can be arranged to form a stunning backdrop that is reflected onto the water’s surface. They need not be partly submerged in water, however, as the thirsty roots can fare just as well in consistently irrigated soil.
This herbaceous perennial can be a vigorous spreader due to its creeping, underground rhizomes. The roots were once believed to have magical features, giving the bearer higher chances of financial gain. In truth, the roots are actually poisonous and can cause intestinal pains when ingested. The sap contains iridin, a flavonoid compound with pharmacological uses.
The official plant of Quebec and the US state of Tennessee, the blue flag iris is naturally found in marshes, streambanks, and meadows in wetland areas. It can also survive in the brackish waters of some estuarine and coastal areas.
7) Purple coneflower (Echinacea purpurea)
Highly adaptable to a variety of soil types and exposure conditions, the purple coneflower makes for a colorful addition to rain gardens, pond edges, and garden slews. It is a member of the Asteraceae or daisy family and is available in several cultivars with slight variations in floral colors. The typical purple coneflower is distinguished by its bright pink to lavender-colored petals. These arise in a slightly drooping manner from solitary flower heads.
This herbaceous species can tolerate wet conditions for limited periods of time. Its capacity for water filtration and the reduction of runoff is emphasized when it is grown in an area where the water can run through rather than settle. It should thus be planted along a slope or close to water sources that tend to overflow. If the roots are in waterlogged soil for too long, they may rot. Intermittent exposure to wetness can be beneficial for the plant, however.
Pollinators find this self-seeding species hard to resist. In optimal conditions, it can quickly crop up in many other parts of the garden. If you wish to avoid reseeding, flowers may need to be deadheaded before they can release their seeds.
8) Winterberry (Ilex verticillata)
An important resource for many birds in the US, winterberry trees are best known for their red fruits, which are able to persist for most of the winter. Also known as fever bush, this tree was once utilized by Native Americans for a wide range of ailments. The berries, along with the leaves and bark, could contain toxic compounds and supposedly reduce blood pressure.
Considered an ornamental tree, the winterberry can be cultivated in boggy areas or rain gardens. In moist soil, it tends to develop into a dense thicket that grows to a height of about 15 feet (4.6 meters). In the wild, this species favors riparian landscapes. It can be used to diversify the borders of a water feature. Mass plantings are perfect for attracting many types of butterflies, bees, and songbirds. The red berries, which stand out like sore thumbs in an expanse of snow, may also attract wild animals.
Winter hardy, tolerant of poor drainage, and perfect for hedges or as foundation plants, winterberry trees are available in an impressive array of cultivars. If you’re intimidated by the full height of this species, there are dwarf cultivars that grow to just 6 feet (1.8 meters) or less. As this species is dioecious, keep in mind that you’ll require both male and female specimens to be within short range of each other for fruit production.
9) Hard rush (Juncus inflexus)
For a no-fuss, hardy addition to a problematic area of the garden, try planting a few tufts of hard rush. This perennial, gray-green grass is distinguished by its hard, leafless stems. It can eventually spread on its own by producing a network of rhizomes. These can aid in conditioning the soil and preventing erosion whenever flooding events occur.
J. inflexus is a low-maintenance and pest-free species that performs remarkably well in moist or wet substrates. It can even survive when submerged in up to 3 inches (7 cm) of standing water, from which it can remove a decent amount of nitrate. It can be grown directly along the margins of ponds or restricted to containers or pots.
In spring & summer, the textural complexity of this species is increased due to the production of rust-colored inflorescences. Some of these may eventually develop into seed capsules. Interestingly, though this species favors wet locations, it is more drought-tolerant than some of its close cousins (including J. effusus). Indeed, it is a truly versatile ornamental grass.
