by Julie Whitacre, Fourth Corner Nurseries
Fourth Corner Nurseries offers 74 species of herbaceous wetland plants available as bare-root divisions. These include several species of Carex, Juncus, Scirpus, Aster, Eleocharis palustris, Typha latifolia, Oenanthe sarmentosa, Deschampsia caespitosa, Glyceria grandis, Sparganium, Distichlis spicata, Mimulus guttatus, Potentilla pacifica, Lysichiton americanum, Veronica americana and Stachys cooleyae. Many of these species are available in large quantities (40,000-100,000). These are all grown from seed, not wild collected. Our seedlings often have higher survival rates than wild-collected plants due to less stressful harvesting techniques, and natural wetlands are not impacted.
In the past, wetland projects have been installed in either spring or fall, however marked differences in plant survival have been noticed. The consensus now is that if you plant in the fall and the plants are dormant under water all winter – they rot and die. If planted in the spring as the water is receding, and then given adequate water the first summer, they live and do fine underwater the following winter. Having some green growth above the water level from the time of planting also seems to be helpful. Physiologically, spring is the season of most active root growth, which probably explains enhanced viability of spring-planted emergents. Spring may be the best time for planting in newly-created wetlands and detention ponds, however care must be taken when enhancing an existing wetland or riparian side-channel area to minimize impact on resident wildlife. Spring is prime breeding time for native birds and amphibians; habitat disruptions at this time can be very detrimental to local populations, even when habitat improvement is the ultimate goal.
Tree and shrub wetland species are available for planting bare-root in December through March, or in containers from late winter through fall. Container trees and shrubs can be planted any time soil moisture is adequate for root establishment, with fall or early spring preferred.
Some conditions to consider when ordering wetland plants include the typical root structure of each species and the habit of top growth. Eleocharis palustris, Juncus balticus, and Scirpus acutus are strongly rhizomatous, and are sold as a piece of rhizome (an underground horizontal stem) having at least two growth points. Some species are rhizomatous, but our seedlings have not yet reached the stage at which rhizomes are developed. Carex lyngbyei, Carex obnupta, Juncus ensifolius, and Scirpus microcarpus are examples; these are sold as seedling divisions. The top growth of most wetland plants dies back in winter. The top height therefore depends on the time of year shipped. Emergents shipped in the winter will arrive having only roots and no top growth, a condition that is more difficult for us to handle during harvest, and for planters to install. This difficulty combined with the observed failure to transplant well at this time has led us to modify our pricing structure. Emergents shipped from mid-November through mid-April are more expensive than those shipped the rest of the year. During the summer and fall, the tops are often cut back to approximately six inches to reduce transplant stress and shipping costs.
In designing wetland mitigation projects, some easy steps can be taken to increase the value of the created habitat for wildlife, including wildfowl, amphibians, and young fish. Birds and amphibians need healthy buffer areas as well as wetlands; buffers can also help improve water quality. Open water areas should slope gradually toward the edges to allow for plenty of shallow water and emergent vegetation habitat. Several different emergent species should be planted, not necessarily randomly-spaced, but in clumps in a mosaic pattern. Various species of Carex produce seed at different times, offering a longer season of food availability. Different species of amphibians attach their eggs to plants with different diameter stems, depending on what they can easily grasp. An ideal plant for amphibian egg-laying has soft stems that stay in the water even as water levels drop. Oenanthe sarmentosa, as well as several other species, have this quality. Stiff-stemmed plants such as Juncus effusus and Scirpus acutus can leave eggs stranded above water if water levels drop. Birds common in wetlands do use the taller vegetation such as Scirpus acutus and Typha latifolia for hiding, but take care, as these particular species often become invasive. Their tendency to take over is great for water-quality treatment ponds, but not necessarily for creating diverse wildlife habitat.
A healthy wetland with diverse plant species, birds, amphibians and many insect species such as dragonflies will naturally have much fewer mosquitoes than a less diverse habitat. In fact, it can be difficult to even find mosquito larvae for sampling purposes in natural wetlands. “Dunks” or other mosquito control measures are not only unnecessary, but are likely detrimental to a healthy ecosystem. The two species of mosquito known to carry West Nile Virus have been found only in disturbed areas such as in tire ruts and unnatural standing water such as in old tires, never in natural wetlands. The best way to minimize mosquito populations, of any species, is to eliminate unnatural standing water and maintain healthy wetland and buffer areas that support predator species such as birds, amphibians and insects.
Many of our native wetland plants are beautiful additions to ornamental ponds, attractive in their own right as well as for the wildlife they sustain. Stachys and Mimulus have showy, colorful flowers, and the Carexes have an under appreciated beauty. Carex mertensii is one of the most graceful of the non-rhizomatous sedges. Watching wildlife attracted to ponds, be it birds, butterflies, dragonflies or frogs and salamanders creates endless opportunities for education, wonder, and relaxation. In an urban setting, you may want to consider the appropriateness of attracting wildlife to your site. Birds can move around fairly easily, but amphibians should not necessarily be encouraged to cross four-lane highways. Also, wildlife may not be the most beneficial visitors to a newly planted wetland. Canadian geese have been known to eat newly-planted Scirpus acutus rhizomes; steps such as netting may be necessary until plants are established.
For more information on wetland vegetation and stormwater management, see the article on the previous page. Whether you need wetland plants for a salmon habitat restoration planting, a water treatment pond, a development mitigation project, or for an ornamental pond planting, please refer to our menu of beautiful, functional, seed-grown emergents.
Thank you to Susan Buis, horticulturist with WSDOT and co-owner of Sound Native Plants, for observations about timing. Thank you to Bob Thomas, wetland specialist with WSDOT, for information about wetlands and mosquitoes.