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Native Plants

General

Native plants provide densely vegetated areas that collect and slow runoff, encourage infiltration, and filter out sediments and soluble pollutants. In addition, native plants are adaptable to most any area, add aesthetic beauty and provide habitat for wildlife.

Native species are applicable on any area in which final grading has been performed. Native species require a longer period of time to become established, and are generally more costly and more difficult to establish than non-native vegetation. However, due to their dense nature and deep root systems, they offer a much higher degree of infiltration and are an attractive alternative to other types of vegetation.

Advantages

  • Cost-effective
  • Drought resistant
  • Low Maintenance
  • Do not require application of fertilizers pesticides
  • Provide a diverse habitat for wildlife

Disadvantages

  • Take longer to establish
  • Require periodic biomass removal by burning or mowing

Design

Vegetation

Native species have vast root systems that may extend more than 10 feet below the surface, allowing them to access hard to reach water and nutrients and grow successfully in poor soils and during dry periods. These extensive root systems also stabilize the soil and protect water quality because fertilizers and pesticides are often not required. Above ground, many species grow in dense clumps that reduce runoff velocities and increase infiltration. Additionally, native species absorb large quantities of water, greatly reducing the amount of runoff that leaves a site.

Native species grow differently than non-native species, as they generally establish their root systems before fully developing above ground. Most native species grow only 2 to 3 inches during the first year while some will lie dormant for up to five years. As a result, the planted area may look less than desirable the first year, consisting more of weeds than native species. In subsequent years, however, the native plants will out-compete the weeds and will begin to flourish.

The species of native vegetation selected will vary greatly depending upon the characteristics of the site. Soil type, slope, site use, maintenance, growth rate, bloom time, hydrology, sun/shade mix, and the time of year it is planted are all factors that must be weighed when selecting vegetation. Information on species selection for use in the shoreland zone can be found on the acceptable native species page. Native species may be established from transplants or seed. Native transplants are available commercially and decrease the time required for establishment by 1 to 2 years, but greatly increase the cost of the practice. Seeding is economical but requires up to 3 years before the plants become established. However, regardless of the species or method selected, careful species selection is crucial. Care should be taken to ensure that the plant or seed is grown locally. Plants or seed of the same species may be obtained from other parts of the country, but may produce less than desirable results. Exotic or invasive species must be avoided.

Erosion Control

To prevent erosion during the establishment period, additional management practices are often required. However, due to the slow germination process, the use of heavy erosion blankets and mats is not recommended as the seed may rot. Rather, clean straw mulch that is free of weeds and other seeds may be used. Mulching rates for use with native species differ than those used for non-native species and it is generally recommended that mulch should be applied at no more than 1 ton per acre.

The use of companion vegetation is also a viable method for controlling erosion during establishment. It provides cover and minimizes weed growth while stabilizing the soil and preventing soil loss. Relatively non-competitive, annual species of vegetation, such as those listed on the Temporary Seeding page may be used for this purpose, provided the seeding rate is cut in half.

Seedbed

Native plants generally do not require extensive seedbed preparation, as a rough surface may actually stimulate certain species of seed. Rather, native species require only 3-4 inches of uncompacted topsoil to grow. If necessary, soils should be deep tilled to relieve compaction.

A sod cutter should be used to remove existing vegetation from the site, as it minimizes the amount of soil that is disturbed during removal. Overturning the soil exposes weed seeds to sunlight and promotes their growth, which creates competition for native species.

Fertilizers should not be used with native species. Not only do native plants not require such amendments, they actually may hinder their establishment by promoting weed growth. Pesticides and irrigation are also generally unnecessary, as native species are well adapted to local conditions.

Seeding

Seed should be applied uniformly following the supplier’s recommendations by broadcast seeding, hydroseeding, or drill seeding. Broadcast seeding involves scattering the seeds on the soil surface by hand or mechanical means and is best utilized on smaller areas and for patching applications. After application, the site should be raked and firmed with a roller or cultipacker. Seeded areas should then be mulched to provide protection for the seed and to reduce erosion before the vegetation becomes established.

Hydroseeding and drill seeding are more costly than broadcast seeding and are used on larger sites to maximize the application’s cost effectiveness. Hydroseeding, a method that mixes the seed and water together into a slurry, is applied on areas that may be difficult to seed with alternative means. Other amendments, such as tackifiers, polymers, and/or fiber mulch are often added to the slurry, which is sprayed on, to protect the seed and to promote its growth. Drill seeding utilizes a drill or cultipacker seeder to inject the seeds beneath the soil surface. Seeding depth should not exceed 1/8 of an inch. Drilling, while more costly than broadcast or hydroseeding, is generally very effective when performed properly because the seed is protected from wind, water, and wildlife.

Maintenance

Native species require little maintenance beyond occasional mowing or periodic prescribed burns. Due to the fact that irrigation and the use of fertilizers, pesticides, and other amendments are unnecessary with native species, long term maintenance costs are generally much less than those associated with non-native species.

Prescribed burns are required every 2-3 years to promote a healthy, diverse landscape. These controlled burns should only be performed once the vegetation has become established, usually during the third or fourth year. Burning clears away old vegetation and non-native species, leaving a warm, clear area that stimulates new growth. In addition, fire provides nutrients for the growing plants from the ash it leaves behind. Because of the potential for injury and property damage associated with this practice, only trained, experienced professionals should perform prescribed burns.

Mowing is required during the first 2 years and may be used as an alternative to burning. Planted areas should be mowed to a height of 6-12 inches 2-3 times during the first year and once during the second year to prevent weeds from developing seed. Native plants grow slowly at first, and mowing to these heights will cause only minor, if any, damage to these species and allows them access to sunlight. During subsequent years, mowing may be performed as an alternative to prescribed burning. Mowing mimics burning by clearing the surface and allowing the sun to warm the soil, without the potential concerns associated with burning. When mowing, clippings should be removed wherever possible.

These activities may be performed at varying times of the year. Varying the time of year that it is performed will stimulate different species and promotes a healthy, diverse ecosystem.

Other maintenance activities should be performed as necessary. If weeding by hand, weeds should be cut as close to the surface as possible to prevent damage to the root systems of native species that may be caused by pulling. Seeded areas should also be inspected after all storm events for evidence of erosion. All necessary repairs should be made immediately.

Construction

  • All grading and tracking shall be completed before seeding begins
  • All management practices should be installed and online before seeding
  • Maximum seed depth of one eighth of an inch
  • To promote growth, seeding should not be performed during excessively wet conditions, as soils may become excessively compacted

Method to Determine Practice Efficiency

Native plants reduce erosion by providing cover and stabilizing the surface. However, due to the length of time required for establishment, no efficiency is given for this practice.

References