Sagittaria latifolia is an emergent aquatic perennial. Due to its arrow-shaped foliage and fleshy tubers, it is often referred to as common arrowhead, broadleaf arrowhead, katniss, swamp potato, and duck potato. Latin Americans call this plant bayoneta or platanillo as it belongs to the Alismataceae family.
Most species under this classification are considered water-plantains and are known for growing in ponds, marshes, and other wetland features. Common arrowhead is native to the Americas, but is now naturalized throughout the temperate zones of the Northern Hemisphere.
Unarguably a distinct identifying feature, the tri-tipped leaves of this plant always look like arrows but are seldom exactly alike in terms of spread and angle. Though they arise as a basal rosette from a single root system, some leaves can be wide or obtuse (like a wedge) whereas others can be narrow and sharply tapered. Veins arise from the base of the leaves and extend almost parallel to one another toward the outer leaf borders.
The flowers are definitely less variable! Stark white blooms occur in whorls of 3 or more on thin stalks that can grow up to 4 feet (120 cm) tall. A tuft of bright yellow stamens arises in the center of 3 delicate petals. The roots are also known for being white and can produce purple-skinned tubers as far as a meter from the mother plant.
Due to its widespread root system, common arrowhead is an aggressive grower. Colonies can quickly take over areas with consistently wet soil. In the wild, individuals can spread to 3 feet when the roots are submerged in shallow water or on the mud banks of swamps, streams, sloughs, and ponds. Fortunately, this potentially invasive plant is associated with many benefits, especially when colonies are well-maintained or when the spread is restricted to small areas.
Common Arrowhead Growth, Hardiness & Climate
S. latifolia is fairly tolerant of polluted water and is known for thriving in both disturbed and pristine wetlands. It is able to withstand slightly turbid water conditions but can struggle to survive when sediment deposition rates are high. Although the roots of this emergent plant are quite strong and can permeate into the deeper layers of soil, it prefers to grow in still or slow-moving water. Wild populations are also known for enduring through wide variations in water levels, as long as the soil stays wet and rich.
Hardy to USDA zones 5 – 11, common arrowhead is tolerant of seasonal temperature variation. Its production period peaks in July, when sun exposure and ambient temperatures are at their highest. A single plant can produce up to 40 tubers when optimal conditions are maximized each year! Keep in mind that if you would like to see production levels at this rate, you will also have to ensure that ammonia levels, salinity, and pH fluctuations are kept at a minimum.
How to Plant Common Arrowhead
Sagittarius latifolia can be planted via seed and propagated via root division. If you intend to use seeds, make sure to begin sowing them in late fall so that young plants can be moved outdoors in the following spring. Seeds may have to undergo cold treatment beforehand to ensure that they germinate within a shorter time frame.
Use a tray setup with a few low pots and approximately 1 – 3 inches of water. Ideally, the soil should stay moist or wet throughout the germination and growing periods. Place your setup in a greenhouse or cold frame to ensure that the seedlings are protected from the elements. Once they are large enough to handle, transplant the individual seedlings into their own pots. You can also plant them in one large pot, but make sure that they are spaced apart as they produce horizontally oriented rhizomes.
Similarly, use a setup that keeps the soil wet for tuber propagation. Tubers should be removed from the mother plant in spring or fall, but they can be planted at any time during the growing period (spring-summer). Bury tubers under approximately 2 – 3 inches of fine organic soil. The pointed tip or hook-like part that extends from the bulb should be facing upwards.
You can mix compost or manure into your soil to enhance its nutrient richness. Once your tubers have produced new roots and leaves, you can move them to their permanent positions. Arrowheads grown out of pots can be moved further into your pond as their leaf stalks lengthen.
How to Care for Common Arrowhead
This species is quite straightforward to care for and is low-maintenance when grown in pots. Colonies that are planted directly into the ground may be challenging to control, especially as they may compete with the rest of your pond edge plants. Keep in mind that this plant spreads via runners or rhizomes underground. In order to prevent self-seeding, you will have to deadhead any spent flowers before they develop into seed clusters.
Common arrowhead isn’t typically associated with serious diseases or pests. If aphids or spider mites tend to plague your other plants, however, they will likely find their way to arrowhead colonies. Monitor the foliage and flower stalks for these pests and manually remove them as soon as they are sighted. If they begin to occur in large amounts, you may have to use a detergent mixture or organic pesticide.
How to Winter Common Arrowhead
Colonies of S. latifolia tubers can survive outdoors through winter. As long as the root systems are situated under a few inches of soil, they should withstand temperatures that drop to as much as -20˚C (-4˚F). The plant’s leaves will naturally die back as temperatures begin to decrease in fall. It is advisable to cut back any remaining leaves before the first frosts occur as the plant’s rootstock will grow dormant through winter.
Make sure to remove any dried or decaying plant parts, especially those that have fallen into your pond water. These will attract bacteria and may decrease your pond’s oxygen levels as they decompose. If located outside of USDA zones 5 – 11, or if your pond freezes over during winter, you may choose to bring marginally planted tubers indoors. Gently dig them out and store them in a cool, dark area to keep them dormant. Replant them the following spring, when the final frosts have thawed.
Is Common Arrowhead Invasive or Toxic?
Common arrowhead is far from toxic, but it can certainly be invasive. This aggressive grower is considered an aquatic weed in several areas (Puerto Rico, some parts of the US) and has officially been declared an invasive plant in Hawaii and French Polynesia. Distribution of the plant is either tightly controlled or prohibited in Europe, Western Australia, and New Zealand. This species was originally introduced into these regions as an ornamental plant, but populations have unfortunately escaped their pondside locations and spread into wild wetlands.
Is Common Arrowhead Edible? Will Fish & Animals Eat it?
S. latifolia is considered a highly edible plant. Its tubers, buds, and seeds are safe for human consumption. The tubers can supposedly be prepared just as you would potatoes. They are best collected in the fall, when they have grown ripe. They can be consumed raw or cooked and may even be pounded into starchy flour. Native Americans regularly harvested and consumed the tubers, which they referred to as ‘wapato’. Currently, the USDA warns against consuming tubers that are harvested from the wild as they are known for accumulating pollutants.
The tubers and seeds are eagerly consumed by animals that range in classification from bird to mammal to reptile. Herbivorous fish may also occasionally graze on the leaves and exposed roots of this species. This plant seems to have a use for all types of animals, so it may be prudent to wait until its organs are developed enough to sustain grazing before placing it outdoors.
Where to Buy Common Arrowhead & Seeds? (UK & US)
Common arrowhead seeds and potted plants can be purchased from plant nurseries or aquascaping shops across its native range. If you are located outside the US, it may be challenging for you to obtain this species from plant stores as it is invasive and may be prohibited. If you are able to acquire your own Sagittaria latifolia, do restrict its spread by growing it out of pots or containers.
