Hydrilla vs. Milfoil

Overview

Hydrilla and watermilfoil are two prominent aquatic plants that share some similarities in appearance and habitat. Both are submerged plants that grow in ponds or lakes and form dense vegetation. These plants are often mistaken for one another, but they have distinct characteristics that set them apart. Understanding their differences is key to managing these plants effectively.

What Does Hydrilla Look Like?

To identify Hydrilla in your waters, look for these key features:

• Stems: Hydrilla stems are green, slender, and capable of growing up to 25 feet long. They branch extensively, forming dense mats near or on top of the surface.
• Leaves: The leaves are small, green, pointed, and arranged in whorls of 4-8 around the stem. They have serrated edges that distinguish them from other plants.
• Flowers: Hydrilla produces tiny, nearly transparent flowers.
• Where it Grows: Hydrilla is non-native plant and can be found in Washington, California, Arizona, and the gulf, southeastern, and eastern states. This plant thrives in slow moving bodies of freshwater and tolerates low light levels, making it challenging to control without the right products.
• How Does Hydrilla Spread? While Hydrilla occasionally reproduces from the male flowers that are released and drift into contact with female flowers, it more commonly reproduces from stem fragments.

What Does Milfoil Look Like?

Milfoil refers to a group of aquatic plants, many of which are native to the United States. However, parrot feather and Eurasian Watermilfoil are the most problematic species due to their invasive natures. Here’s how to recognize most types of milfoil:

• Stems: Milfoil stems are spaghetti like, long and flexible. They can grow to over six feet long and branch prolifically at the water’s surface. Stems can be peach to pink to even reddish in color.
• Leaves: The feathery, finely divided leaves are arranged in whorls of four to five around the stem and are spaced one half to one and a half inches apart. Some variations of watermilfoil don’t have leaves that stand up above the water’s surface, and some do. Parrot feather and variable leaf milfoil have rigid leaves that stand above the surface a few inches to a foot.
• Flowers: These plants have flower spikes that are on the same stems as the leaves. They stick out of the water, and tiny reddish flowers whorl around the stem.
• Where it Grows: Multiple types of watermilfoils can be found across the United States and grow in slow moving bodies of freshwater.
• How Do Milfoils Reproduce? Most milfoil weeds reproduce from fragments or roots. Some produce winter buds.

Differences Between Most Milfoils and Eurasian

While native milfoil species are less aggressive and grow in a more balanced manner, Eurasian milfoil exhibits rapid growth, starting earlier in the season and quickly outcompeting other vegetation. This aggressive growth allows Eurasian milfoil to form dense, sprawling mats that can overshadow and choke out native aquatic plants, disrupting the natural balance of the ecosystem.

In contrast, native milfoils grow with more control, integrating into their environments. They serve an important role by providing food for some waterfowl and offering shelter for microorganisms, creating a supportive habitat for aquatic life rather than dominating it.

Milfoil vs. Hydrilla

While Hydrilla and milfoil share some similarities as submerged aquatic plants, they have many differences that stand out. One of the most noticeable differences is in their leaves: Hydrilla’s leaves are small and pointed while milfoil has delicate, feathery leaves, giving it a lighter appearance compared to Hydrilla’s rigid and spiny look. Hydrilla is more adaptable and can grow in low light and will form dense mats if not controlled. Eurasian watermilfoil can develop canopies, blocking out light for native species, and spreads rapidly through fragmentation.

How to Control Hydrilla?

An herbicide and algaecide combination is the best way to kill hydrilla, as mechanical control can be difficult. Hydrilla can regrow from any fragments, roots, or tubers left in the water. Dibrox is a fast acting contact herbicide that sinks down in the water to control submerged weeds. Mizzen is an algaecide, but it is needed for hydrilla control and should be used alongside Dibrox for complete eradication of this plant. These two products can even be mixed together with water in a sprayer for a faster application.

How to Control Milfoil?

How to Get Rid of Milfoil in Ponds?

Dibrox is a highly effective solution to kill milfoil in ponds, particularly Eurasian. This product is an ideal solution for areas where the milfoil has formed dense mats that interfere with pond use.

How to Get Rid of Milfoil in Lakes?

Dibrox is an effective solution for milfoil control in lakes in addition to ponds. Another herbicide, Hydrothol, is a granular solution for milfoil and it can provide partial control of Hydrilla as well. This product is toxic for fish if they are trapped in a pond, but in a larger body of water the fish will sense it and stay away until the product is neutralized.

2, 4-D is another good option for lakes. This product comes in liquid or granules. The liquid form is diluted and sprayed over the treatment area, and the granular form is broadcast evenly over submerged weeds.

Conclusion

Hydrilla and milfoil are two notorious aquatic plants that share some similarities in appearance and habitat. Both are submerged plants that form dense vegetation. Despite their shared features, they differ in structure and growth habits. Identifying these plants accurately is crucial for maintaining a healthy aquatic ecosystem and addressing any management needs effectively.