The Best Bog Plants & Best Marginal Pond Plants 2021 (Top Filter Plants)
Marginal plants are those that prefer to have their roots and crown wet, and as such grow in shallow water, or soil that is consistently saturated. Bog plants can grow in standing water for short periods, but are really adapted to only have their feet wet, not their stems or leaves; as such, they are best suited to constantly damp soil as opposed to standing water.
These are among some of the most important plants, primarily due to their ability to filter and clean water, provide dissolved oxygen directly to the water, and soak up excess nutrients and pollutants. The plants and soils of bogs and wetlands actually act as a sort of sponge, protecting the area from flooding, runoff, and so on.
In addition, they are necessary for a large variety of organisms. Frogs and other herps (a group that includes reptiles and amphibians) depend on them cover from heat and predators, and may also lay their eggs on them; waterfowl utilize them for cover, food, and to construct nests depending on the species; fish may hide within or under marginal plants, and some may nibble on the roots and leaves if it’s a plant that they find palatable; they also provide critical habitat for aquatic invertebrates, which are toward the bottom of the food chain and depended on for food by birds, fish, herps, and mammals alike.
How To Choose Ideal Marginal & Bog Plants:
1) Hardiness Zone
When deciding which bog or marginal plants to incorporate into your pond, there are a few things that you should be aware of. Plant hardiness is important – be sure to check which hardiness zone that you live in, and from there you will be able to determine which plants are best suited to that particular zone. Each continent has its own hardiness zone criteria, and can be found relatively easily with a quick online search.
2) Size, Growth Rate & Invasiveness
In addition, you will need to research the plants themselves. Size is an important characteristic to take into consideration – you don’t want plants that are too large for your pond, spread too quickly or slowly to suit your needs/desires, and so on. You will also need to be absolutely sure that the plant(s) you’re considering are not an invasive species in your area, as they could very easily wreak havoc on your pond ecosystem or escape and cause even greater damage to the surrounding natural ecosystems.
Ease of care is also important, and how much time that you have to take care of the plants. Some may require frequent trimming or cutting, others may need to be treated for pests, and still others must have very specific water conditions (such as pH, alkalinity levels, etc.) that you’ll need to regularly monitor in order for them to survive.
3) Plant Sensitivity (Area Quality)
You’ll also need to take into account the overall quality of your area. Again, some plant species require specific conditions, while others are very sensitive to pollutants. Along these same lines, you’ll need to know the plant’s effectiveness of filtering nutrients if you live in an area with significant runoff (like if you live within a low elevation river basin that is prone to flooding and thus carrying all manner of nutrients and pollutants from the surrounding area to your property).
Keeping all of these factors in mind, below we will explore some of the best bog and marginal plant species for your pond.
There are many species of arrowhead, but perhaps the most well-known is the common arrowhead (Sagittaria sagittifolia), which grows well in either very moist soils or several inches of standing water. It has tuberous roots that are loaded with nutrition, which were historically eaten by Native Americans in the U.S., and are also munched on by a variety of fish species. The arrowhead shaped leaves are particularly adept at producing oxygen above water, while the thick roots and stems are adept at releasing oxygen directly into the water. Its robust build also makes it a suitable filter species, able to soak up and cycle excess nutrients, particularly phosphorous.
Ecologists also often use this plant to not only filter nutrients, but also to help stabilize shorelines and protect them from erosion. In addition, it’s an attractive plant, producing beautiful white three petaled flowers that pollinators are likely to visit regularly.
Bulrushes belong to the cattail family (Typhaceae), and can be both emergent and bog species, able to grow both in damp soils as well as standing water up to three feet deep. They grow tall, ranging from 1 to 8 feet depending on the variety, with stiff stems and dense root clusters that soak up nutrients and help stabilize banks. In addition, bulrushes provide cover for waterfowl, other birds, and fish in shallow waters that would otherwise be open and make them an easy target for predators. Because they grow in clusters, they are fairly easy to remove if they start to spread too much for your liking.
Despite its misleading common name, scouring rush does not belong to the same family as bulrushes. However, it, too, is wonderful at removing pollutants and filtering water. It’s commonly also called horsetail, but this is technically incorrect – though similar, and both awesomely prehistoric, horsetails and scouring rushes are distinctly different species. Despite this slight differentiation, they perform similar duties and both make great additions to ponds. They are segmented, with each one to two inch long segment capable of holding approximately half of a teaspoon or more of water. As the water flows up the plant into these segments, it gets filtered. It is then held within these individual segmented chambers until the plant needs it if a drought occurs.
Indigenous people figured out long ago that, in times of need, these segments can be snapped off and the clean water sipped out. So long as the entire plant isn’t torn up, it won’t harm it – the horsetail or scouring rush will simply begin to regrow from the segment joint. They also have a very unique (and indeed prehistoric!) look to them, making them an eye-catching marginal decoration.
Following our theme of rushes, next up is the bur reed, which despite its common name is actually more closely related to a rush than a reed and is also a member of the cattail family (Typhaceae). This is typically a bog plant, so it prefers damp soils as opposed to growing in standing water. This makes them especially useful in filtering water (such as rain, floodwater, runoff, etc.) before it is able to reach your pond. Biologists and ecologists also commonly plant them to stabilize banks in wetland and riparian restoration projects, while also providing cover for smaller wildlife. It’s not considered a particularly great competitor, and while it’s deemed stable right now, it is in need of protection due to a combination of pollution, invasive species and its inability to compete with them for space and resources, and overall habitat degradation around the world.
Belonging to the buttercup family (Renunculaceae), marsh marigolds do best in moist soils, but can tolerate standing water so long as it’s not for prolonged periods of time. Like most bog plants, they’re well-suited to filtering water and pollutants. And like most bog and marginal plant species, they require little care; one consideration is that they do need partial shade. An added perk of marsh marigolds is that they are exceptionally hardy, and begin blooming in very early spring while temperatures are still below freezing. Because of this, not only do they help beautify your pond both early and late in the year, they also give pollinators their first and last taste of nectar – this is essential as pollinators, such as bees and hummingbirds, are in dire need of nectar both when they are coming out of dormancy in early to late spring and about to enter it in early to late autumn.
Marsh milkweeds function similarly to marsh marigolds, providing filtration benefits, bank stabilization, beautification, and a wonderful nectar and pollen source for a variety of insects and birds (particularly the endangered monarch butterfly). Their pollination system is quite unique and fascinating – their pollen are stored by the thousands in tiny sacs called pollinia, and two pollinia are connected to each other by a string-like structure. When an insect lands on the milkweed, it slips on a steep structure of the flower called the horn, so that the string of the pollinia winds up draped over the insect sort of like saddlebags. The insect then flies off, carrying the pollen to other plants and thus pollinating them! No other plants other than milkweed species are known to have a pollination system like this.
Blue flag water iris is an attractive perennial flowering species that most often grows on water shores in moist soil, but can grow in up to six inches of water. It’s hardy, able to withstand both drought and flooding, with very low potential to become a nuisance species or spread out of control. They germinate readily, with typically a 100% success rate when planted from seed, though they should be planted in early spring while the soil is still cold (but not frozen) and at the very edge of the water where the soil is thoroughly saturated but not underwater. Like most of the other plants in this article, blue flag aids in bank stabilization and help to cycle nutrients.
Water plantain, so named because of its starchy, fibrous roots that resemble plantains, is an emergent (another name for bog) plant, preferring to grow in very shallow, calm water. It needs full sunlight and silty soils, but otherwise is a pretty resilient plant that doesn’t need much in terms of care. The broad leaves provide habitat and shelter for fish, herps, and birds (as well as a perching place for the small members of this group), while the roots filter water and also provide food for fish and waterfowl. They also produce nutlets that are readily consumed by waterfowl, and their roots and stems provide breeding and rearing areas for fish while also helping to stabilize the sediment to reduce erosion.
Also known as pickerelweed, this plant grows well in either saturated soils or standing water, making it ideal for both bank stabilization as well as usage as a bog filter plant. It belongs to the water hyacinth family, and produces small, striking purple-blue flowers arranged tightly on a spike inflorescence that makes them appear like one large, tall, spike-shaped flower. These flowers provide not only nectar and pollen for pollinators, but also a valuable breeding and living area for a variety of useful insect species. Their rhizomes mean that it’s easy for them to spread, so you may have to cut them back from time to time to keep them from overtaking your pond, or you could simply plant them in pots that restrict their spread.
However, the latter method will also hamper their ability to stabilize the bank sediment and help reduce water disturbance, which are both reasons why aquatic biologists utilize sometimes this plant in restoration projects. Their broad leaves also provide habitat and hiding for fish as well as some waterfowl and passerine species.
Closely resembling a cattail if only glanced at briefly, sweet flags are actually a tall perennial herb that grows best in water that is anywhere from a few inches to up to three feet deep. Unlike cattails, sweet flags don’t possess rhizomes, so they don’t multiply to become a nuisance species. Their flat, long, deep green leaves can lend an almost tropical-like appearance to your pond, and their characteristic sweet, spicy scent can further this impression. They provide oxygen directly into the water, help soak up excess nutrients (like the rest of the plants in this article), aid in bank stabilization, and offer important spawning habitat for a variety of fish. Be sure to purchase/plant only native varieties, and not Japanese sweet flag, as this specific species is an invasive in North America and Europe.
A highly recognizable species found in most freshwater habitats in the Midwest, water arum has broad, large heart-shaped leaves that grow up to a foot in diameter and a unique white spathe flower. It prefers full shade, and can grow in either damp soil or very shallow water. It doesn’t do well in below freezing temperatures, so a simple method to protect it is to place a layer of mulch around the plant in autumn to protect it from freezing. Water arum provides habitat and breeding area for fish and aquatic invertebrates, and the small berries that it produces eaten by many types of wildlife – bird, fish, and mammal alike.
So named after the slender, long green fruits they produce that resemble lizard tails, this plant grows well in either sunny or shady conditions and produces white flowers with an energizing citrus-like aroma. They can be planted in either damp soil or shallow water, providing erosion control, water oxygenation and purification, and habitat for fish, insects, and waterfowl. If your pond has significant water movement or the area is prone to high rainfall or flooding, you should plant the lizard’s tail in a dense substrate that will hold it in place, as their roots aren’t overly strong and they are prone to washing away if too much disturbance occurs. In addition, this plant is only native to the eastern U.S., so be aware of this before purchasing.
However, it’s also considered an endangered species, so if it’s native to your area, planting it may be a boon to the ecosystem and assist in the survival of the species as well as species that depend upon it.