Exclosures

General

Establishment of native aquatic plants in lakes and reservoirs requires protection from grazers. In most cases, 2" x 4" mesh wire is adequate to exclude common grazers such as carp and turtles. In some cases, smaller mesh may be required (1" diamond mesh excludes nearly all problematic grazers). We recommend conducting small-scale tests to ascertain the levels of protection from grazers in any particular water body.

Fences and pens: large-scale protection

Several fence designs are used in aquatic plant restoration efforts. Cove fences are constructed across the mouths of coves to exclude water-borne grazers such as common carp and semi-aquatic turtles from planting sites. Shoreline fences exclude these same grazers, as well as terrestrial herbivores when a backing is installed. By adding erosion fencing to a shoreline fence (silt fence), wave action can be reduced.

All of these fences are constructed from t-posts (8-10' spacing) and 2" x 4" welded-wire. After t-posts are set, the wire is attached using aluminum wire ties. Galvanized welded-wire will last about 2 years in most lakes. We recommend using PVC coated wire to extend the longevity of the exclosure. Welded-wire should extend 1 foot or more above expected water levels, and the bottom of the wire should be firm against the substrate at all points. Addition of a 2' wide flange (using plastic construction fencing) is recommended at the bottoms of fenced coves. Safety caps should be installed on all t-posts.

Fenced cove, shoreline fence and silt fence general layouts.

Fenced cove, planted.

Shoreline fence without backing.

Shoreline fence with backing, planted.

Some sites are suitable for construction of free-standing pens, constructed from the same materials as fences. Large, flat areas that are somewhat protected from wind and waves. Pens used in restoration efforts have ranged from 8' x 8' to 100' x 100'. As in fenced coves, we recommend adding a bottom flange to larger pens (25' x25' and larger).

Free-standing pen, general design.

Free-standing pen, installed and planted.

American lotus expansion from free-standing pens.

Cages: small-scale protection

Tomato cages are easily constructed and serve to protect single emergent (and some submersed) plants. 2" x 4" mesh welded-wire is cut into 5-10' lengths, rolled into cylinders, and ends fastened using c-rings (or hog rings). The resultant tomato cages (1.5-2.5' in diameter) are sufficient for protecting single plants. Tomato cages should be anchored using earth staples or tent stakes. 14-gauge PVC-coated welded-wire is recommended for these cages.

Tomato cage, general design.

Tomato cage, installed and planted.

Ring cages are large versions of tomato cages, and are used for floating-leaved (water lilies) and most submersed species. This cage type permits establishment of larger founder colonies, and minimizes stem damage due to abrasion against cage materials. Construction and materials are similar to that used in tomato cages, with wire cut at greater lengths to increase cage diameters to 5-6 feet. Heavier wire (12 gauge, PVC coated) is recommended for cage stability.

Ring cage, general design.

Ring cage, installed and planted.

Hoop cages are another version of tomato and ring cages that allow for planting submersed species at greater depths. Hoop cages are taller (6') and always constructed from 12 gauge, PVC coated wire. Twenty-five foot lengths of wire are cut and formed into cylinders about 7' in diameter. Because of their height, hoop cages tend to be unstable, and hoops of 1" diameter plastic irrigation tubing are attached to the top and bottom of the cylinder for structural support. The cages are then anchored by weaving PVC piping through the mesh and pressing the pipe into the bottom mud.

Hoop cage, general design.

Hoop cage.

Tray cages are designed to protect roots, stem bases, and basal rosettes of emergent and some submerse species. The cages are constructed from 2" x 4" welded-wire (as seen below). Shorter trays (8" tall) are suitable for emergent plants, while taller trays (12") are best for submersed species.

Tray cage, general design.

Tray cage, installed and planted.

Tetra-weedrons are floating cages designed to promote establishment of the non-rooted coontail (Ceratophyllum demersum) in lakes that fluctuate widely. These cages are constructed from 1.5-2" diamond mesh construction fencing and tethered to anchors in water depths typically not exposed in a given reservoir.

Tetra-weedron, general design.

In-lake nurseries (kiddie pool nurseries) enable local production of strong propagules (potted plants) for restoration projects. The diagram below describes step by step installation (and materials needed) for in-lake nurseries.

In-lake nursery, general design and installation.