Types of Aquatic Weeds in Florida and How to Control Them

If you manage a lake, pond, stormwater system, or canal in Florida, you already know the truth: aquatic weeds do not “wait until you have time.” With warm temperatures, long growing seasons, frequent rain, and nutrient runoff, many Florida waterways can go from “looks fine” to “fully choked” in a surprisingly short window.

The good news is that most aquatic weed problems are manageable if you do two things well:

1. Identify what you are dealing with (the right ID changes everything).

2. Match the control method to the plant, the site, and your goals.

Below is a practical guide to the most common types of aquatic weeds in Florida and the most reliable ways to control them, especially for ponds and lakes along the Gulf Coast.

Why aquatic weeds take off in Florida

A few factors make Florida waters especially weed-friendly:

• Warm water for most of the year, so plants keep growing when other states slow down.

• High sunlight and shallow areas that let plants root and spread.

• Nutrient inputs from fertilizer runoff, grass clippings, septic seepage, and waterfowl waste.

• Stable water in ponds and stormwater systems, which favors dense plant growth.

A little vegetation can be beneficial, but nuisance growth can reduce oxygen, block drainage, interfere with recreation, and damage fish habitat when it collapses or decays.

Quick way to classify aquatic weeds (so you can narrow the ID fast)

Most aquatic plants fall into one of these groups:

• Floating weeds (free-floating on the surface)

• Submerged weeds (mostly underwater)

• Emergent weeds (rooted underwater but growing above the surface)

• Algae (true algae or cyanobacteria, not “plants” in the usual sense)

Let’s walk through the most common problem species in Florida and what control typically looks like.

Floating aquatic weeds in Florida

Floating weeds spread fast because they do not need to root. Wind can pile them into coves and shorelines overnight.

1) Water hyacinth (Eichhornia crassipes)

How to spot it: Glossy round leaves, swollen “spongy” stems that help it float, purple flowers when blooming. Forms thick surface mats.

Why it’s a problem: Blocks light, reduces oxygen, clogs intakes, and restricts access.

Control options:

• Herbicides: Systemic products are commonly used. Timing matters, and thick mats often require follow-up treatments.

• Mechanical removal: Works well for heavy infestations, especially when you need immediate open water. Disposal planning is important.

• Prevention: Reduce nutrients and avoid spreading fragments between water bodies.

2) Water lettuce (Pistia stratiotes)

How to spot it: Velvety, light-green rosettes that resemble floating lettuce. Dense mats form quickly in calm water.

Why it’s a problem: Similar to hyacinth, plus it can cover shorelines and trap sediment.

Control options:

• Herbicides: Often effective when applied early before mats get too thick.

• Physical removal: Helpful in smaller ponds or when mats are concentrated by wind.

• Nutrient control: Can reduce how aggressively it rebounds.

3) Duckweed (Lemna spp.) and giant duckweed (Spirodela spp.)

How to spot it: Tiny floating green “dots” that can coat the surface like paint. Giant duckweed is slightly larger.

Why it’s a problem: A full surface blanket reduces oxygen exchange and can trigger fish stress, especially during hot, still weather.

Control options:

• Herbicides: Can work, but it often requires a plan for follow-up because duckweed rebounds quickly if nutrients remain high.

• Aeration and circulation: Makes conditions less favorable and reduces surface stagnation.

• Nutrient management: This is the long-term lever with duckweed.

4) Salvinia (common salvinia and giant salvinia)

How to spot it: Floating fern-like plant. Leaves occur in pairs with a “hairy” texture. Giant salvinia is more aggressive and forms thick, layered mats.

Why it’s a problem: Extremely fast spread, severe surface coverage, major oxygen impacts.

Control options:

• Early detection and rapid response: This is one where “wait and see” gets expensive fast.

• Herbicides and removal: Often used together depending on coverage and site constraints.

Submerged aquatic weeds in Florida

Submerged weeds are the ones you feel on your feet and see trailing under the surface. They can be rooted or free-floating under the water, and many spread by fragments.

5) Hydrilla (Hydrilla verticillata)

How to spot it: Submerged plant with small pointed leaves in whorls around the stem. Often forms thick underwater “walls” and can top out at the surface.

Why it’s a problem: One of Florida’s most notorious invasive plants. It grows fast, crowds out natives, and fragments easily (each fragment can start a new colony).

Control options:

• Herbicides: Submerged treatments require the right product and correct water-use considerations. Whole-pond strategies are often different than spot treatments.

• Grass carp (where allowed): Can provide longer-term suppression in certain ponds, but stocking rates and expectations need to be realistic.

• Mechanical harvesting: Can open lanes quickly, but it may increase spread if fragmentation is not managed.

6) Eurasian watermilfoil (Myriophyllum spicatum)

How to spot it: Feather-like leaves in whorls, soft and “bushy.” Often forms surface canopies.

Why it’s a problem: Spreads by fragmentation and can dominate shallow zones.

Control options:

• Selective herbicides: Often effective with good timing.

• Physical removal: Can work in small areas, but fragments must be contained.

• Shoreline management: Preventing shallow sediment buildup helps reduce expansion zones.

7) Coontail (Ceratophyllum demersum)

How to spot it: A submerged plant with stiff, forked leaves that look like a bottle brush or raccoon tail. Often free-floating but can tangle in dense mats.

Why it’s a problem: Can fill the water column and create thick underwater masses.

Control options:

• Herbicides: Can be controlled, but treatment choice depends on whether the plant is rooted or free-floating and on waterbody use.

• Raking/harvesting: Useful for small ponds and swimming areas, but expect regrowth if conditions stay favorable.

8) Naiad (southern naiad, Najas spp.)

How to spot it: Slender stems with narrow leaves, forms underwater stands.

Why it’s a problem: Can expand quickly in nutrient-rich, warm water and interfere with boating and fishing.

Control options:

• Herbicides: Often manageable with correct timing.

• Nutrient reduction: Helps prevent heavy annual blowups.

Emergent aquatic weeds (shoreline and shallow-water invaders)

Emergent plants are rooted in the bottom but grow above the surface. They can stabilize shorelines in moderation, but invasive species can create monocultures and restrict access.

9) Cattails (Typha spp.)

How to spot it: Tall, upright leaves with the classic brown “hot dog” seed head.

Why it’s a problem: Can overtake shorelines and shallow shelves, narrowing open water and changing habitat.

Control options:

• Targeted herbicide applications: Often used for selective thinning or removal.

• Physical removal: Digging and cutting can work for small stands, but you must address the root/rhizome system or it returns.

• Water level management (when possible): Sometimes used as part of an integrated plan.

  
  

10) Alligator weed (Alternanthera philoxeroides)

How to spot it: Grows along shorelines and into water, with opposite leaves and small white clover-like flowers. Forms dense floating and emergent mats.

Why it’s a problem: Spreads aggressively, blocks shorelines, and can grow from fragments.

Control options:

• Herbicides: Often effective with the right approach, but repeat treatments may be needed.

• Mechanical removal with containment: Avoid spreading fragments.

11) Torpedograss (Panicum repens)

How to spot it: Grass-like plant in wet shorelines and shallow water. Strong, creeping rhizomes (underground stems) that “torpedo” through soil.

Why it’s a problem: Very difficult to eliminate once established because of deep, persistent rhizomes.

Control options:

• Integrated control: Typically requires repeated treatments and a long-term plan.

• Restoration: Replacing with desirable shoreline vegetation can help prevent reinvasion.

12) Water primrose (Ludwigia spp.)

How to spot it: Emergent and floating growth, often with yellow flowers depending on species. Forms thick shoreline mats.

Why it’s a problem: Spreads along edges, traps sediment, and can creep into open water.

Control options:

• Herbicides: Often used for shoreline bands and encroaching mats.

• Shoreline shaping and maintenance: Reduces the shallow “shelf” that primrose loves.

Algae problems (often mistaken for “weeds”)

Algae is normal in Florida water, but nuisance algae can take over quickly when nutrients and sunlight line up.

13) Filamentous algae (string algae)

How to spot it: Green hair-like strands that form floating mats, especially in spring and early summer. Feels like wet wool.

Why it’s a problem: Covers shorelines, tangles fishing lines, looks bad, and can contribute to oxygen swings when it dies off.

Control options:

• Algaecides: Often give fast results, but dosing and timing matter to avoid oxygen depletion events.

• Aeration and circulation: Helps reduce stagnation and supports more stable dissolved oxygen.

• Nutrient management: The long-term fix, especially reducing phosphorus inputs.

14) Planktonic algae blooms (green water)

How to spot it: Water looks like pea soup or green paint. You cannot see very far below the surface.

Why it’s a problem: Can lead to large oxygen swings, fish kills, and in some cases harmful algae concerns.

Control options:

• Identify what’s actually blooming: Treatment strategy changes depending on whether it’s typical algae or cyanobacteria.

• Aeration: Reduces stress and helps stabilize oxygen.

• Nutrient reduction: Usually the core long-term solution.

What control method works best? (A practical overview)

Most Florida aquatic weed management plans use a mix of these tools:

Mechanical removal

Best for: Immediate access needs, heavy surface mats, localized problem areas. Pros: Instant results, no chemistry in the water at the time of removal. Cons: Can be expensive at scale, disposal is required, and fragmentation can spread certain plants.

Herbicide treatments

Best for: Most established infestations, especially when applied early and correctly. Pros: Efficient and scalable, can be selective depending on product and technique. Cons: Requires proper licensing, timing, and attention to water-use restrictions. Poorly planned treatments can cause oxygen issues if too much vegetation dies at once.

Biological control (where appropriate)

Examples: Triploid grass carp (in approved situations), beneficial insects for certain invasives in larger systems. Pros: Can provide ongoing suppression. Cons: Not a quick fix, not suitable for every waterbody, and results vary.

Habitat and nutrient management

Best for: Preventing repeat blooms and reducing long-term cost. Examples: Reduce fertilizer runoff, install buffer plantings, manage stormwater inflows, add aeration, remove excess organic muck in targeted cases. Pros: Improves overall waterbody health. Cons: Takes time and usually works best alongside active weed control.

A simple “what should I do next?” checklist

If you are staring at a weed problem and want a clear next step:

1. Get a correct ID. A wrong ID leads to wasted money and poor results.

2. Estimate coverage. A few patches is different than 60 percent surface coverage.

3. Decide your goal. Total removal is not always ideal. Many ponds do better with controlled, beneficial vegetation.

4. Avoid treating too much at once. Rapid die-off can reduce dissolved oxygen.

5. Plan for follow-up. Most invasive plants need repeat attention, especially in Florida.

6. Address nutrients. If the pond is being “fed” by runoff, weeds and algae will keep coming back.

When it makes sense to call a professional

If you are dealing with any of the following, it’s usually worth getting an expert involved:

• You suspect hydrilla, giant salvinia, or a heavy hyacinth infestation

• Your pond has fish, fountains, aerators, irrigation use, or public access considerations

• You have recurring algae blooms every warm season

• You need documentation or a long-term management plan (common for HOA and commercial ponds)

• You want results without the trial-and-error cycle

  
  

Gulf Coast Aquatics has spent the last 30 years managing lakes and ponds along Florida’s Gulf Coast, and a big part of that job is matching the control method to the plant and the property. If you want a clear plan and realistic pricing, you can reach out to Gulf Coast Aquatics for a quote and get recommendations based on your exact waterbody and goals.

Final thoughts

Florida aquatic weeds are not going away, but they are controllable. The key is recognizing what type of plant you have, treating at the right time, and pairing control with prevention so you are not fighting the same battle every month.

If you take one thing from this guide, let it be this: identify first, treat second, and plan for maintenance, because that is what keeps Florida ponds and lakes healthy year-round.