"Restorationists endeavor to establish natural habitats by planting and nurturing diverse assemblages of native plant species. Newly created sites are often invaded by fast growing weedy species which need to be controlled while the more slowly growing desired species mature. As a restorationist, I am always interested in finding the most efficient and cost-effective path to success based on sound science. The idea is to "tend the garden" for as little as necessary to allow for the restored habitat to function based on natural processes as soon as it can. FIPR's research concerning the control of weeds on restoration projects has improved our understanding of how much control is excessive and has also provided us with some "silver-bullet" technology for selectively eliminating some weeds without adversely affecting our desired plants. This is valuable research, and I have often put the results of FIPR-funded studies into practice just as soon as they are published."

John Kiefer, P.E., PWS
Manager Environmental and Ecological Services
BCI Engineers and Scientists, Inc.

Native Habitats - Phosphate companies are required to prepare reclamation plans that must be approved by state and local regulatory agencies before the first shovel of dirt can be dug; however, agreeing on the best way to reclaim mined lands is sometimes a struggle. One FIPR research focus is to develop land reclamation and restoration techniques that are not only effective but also efficient and economical.

Although government regulations are intended to foster good reclamation, occasionally they may actually hinder the process. One example is a requirement to limit the presence of so-called "nuisance" species, such as primrose willow and cattail, in wetlands. Compliance often requires extensive use of herbicides or mechanical means to control these plants, which may have detrimental effects on other more desirable trees and understory plants. In forested wetlands, such efforts are not necessary for control of these particular "nuisance" species. FIPR research has shown that wetland trees are able to grow in the presence of primrose willow and cattail and that the primrose willow and cattail will be shaded out as the tree canopy develops. Rather than "nuisance" species, primrose willow and cattail should be considered as early successional species that aid in absorption of nutrients and in organic matter accumulation and soil development. Shade from primrose willow also aids the establishment of shade-requiring understory plants.

Besides dealing with "nuisance" plant species, the control of exotic weeds has been a major complication in reclaiming lands to native habitat. The purpose of this research has been to evaluate the competitive effects of various weeds and nuisance plant species on the establishment and growth of native plants on uplands and wetlands on reclaimed phosphate mined lands in Florida, and to develop cost-effective weed management and control strategies.

In research on forested wetlands, several long-term experiments have the following objectives: (1) evaluate the competitive effects of primrose willow, cattail, and elderberry on wetland tree growth; and (2) determine if trees can shade out primrose willow, cattail and elderberry. The objectives of the upland research are to: (1) evaluate weed competition; (2) develop and evaluate strategies for control and management of weeds in reclaimed native upland habitats, with emphasis on exotic grasses such as cogongrass, natalgrass, bermudagrass, bahiagrass and torpedograss; (2) identify and evaluate selective and nonselective herbicides (e.g., Plateau®, Fusilade®, Roundup®, Arsenal®) and optimize rates and times of application; and (3) evaluate cover crops (trees, shrubs and herbaceous ground cover) for their abilities to compete with and suppress weeds, yet be compatible with strategies for establishing desirable vegetation.

Following are abstracts from papers given on this research.

WEED CONTROL AND UPLAND NATIVE PLANT ESTABLISHMENT
ON PHOSPHATE MINED LANDS IN FLORIDA

Presented at 30th Annual Conference on Ecosystems Restoration and Creation, Tampa, FL, October, 2003. Sponsored by Hillsborough Community College

Steven G. Richardson, Nancy Bissett, Cathy Knott and Kate Himel
Florida Institute of Phosphate Research, Bartow, FL

Abstract: Research was conducted to examine the effects of imazapic (Plateau®) herbicide at different rates and times of application on several native and non-native upland plant species at several mined sites and one unmined site in central peninsular Florida. The effects of weed removal on Aristida beyrichiana and Sorghastrum secundum were also studied at a mined site. Imazapic applied just after seeding in early December greatly inhibited the germination and emergence of most species, both native and weedy. Several weed species, including natal grass (Rhynchelytrum repens), seedling bahiagrass (Paspalum notatum), crabgrass (Digitaria spp.), and nutsedges (Cyperus spp.) were controlled with 0.14 kg a.i./ha of imazapic (8 oz/acre of Plateau®) or more applied either pre- or post-emergent. Imazapic applied post-emergent (late May through early October) at rates of 0.14 to 0.21 kg a.i./Ha (8 to 12 oz/acre Plateau®) caused little or no damage to Andropogon spp., Aristida beyrichiana, Eragrostis spp., Liatris spp., Chaemaechrista nictitans, Pityopsis graminifolia, Schizachyrium scoparium var. stoloniferum, and Solidago stricta. Unfortunately, Sorghastrum secundum was severely injured by imazapic.

RESPONSES OF TWO NATIVE AND TWO NONNATIVE GRASSES
TO IMAZAPIC HERBICIDE ON PHOSPHATE MINED LANDS IN FLORIDA

Paper presented at the 17th Annual Meeting of the American Society for Surface Mining and Reclamation, Tampa, Florida, June 11-15, 2000.

R. A. Kluson, S. G. Richardson, D. B. Shibles and D. B. Corley
Florida Institute of Phosphate Research, Bartow FL

Abstract: Successful reclamation of upland habitats on phosphate mined lands in Florida requires control of invasive, nonnative weed species without detrimental effects on the revegetation of native plant species. To address this problem we have researched the post-emergence application of the new selective herbicide imazapic (Plateau®) on two native and two invasive grasses. For example, imazapic tolerance (0.05 to 0.21 kg a.i./Ha) was tested on the native species wiregrass (Aristida beyrichiana Trinius & Ruprecht) and lopsided indiangrass (Sorghastrum secundum [Ell.] Nash) in the greenhouse and in the field on reclaimed overburden soil. We also evaluated the rate effects (0.07 to 0.21 kg a.i./Ha) on the invasive nonnative species natalgrass (Rhynchelytrum repens [Wild.] C.E. Hubb) and bahiagrass (Paspalum notatum Fluegge) on reclaimed sand tailings soil. In the greenhouse, both lopsided indiangrass and wiregrass showed sensitivity to imazapic damage, but the reduction in foliar growth of indiangrass occurred at lower rates and was longer lasting. Under more stressful growing conditions in the field, however, wiregrass showed tolerance to imazapic, and only lopsided indiangrass showed sensitivity to the same imazapic rates. The effects on indiangrass included reduced survival and percentage of green foliage. Interestingly, older indiangrass plants (31 months) were more susceptible than young plants (3 months). Imazapic reduced cover and plant vigor of both natalgrass and bahiagrass in the field, but the effects on natalgrass were evident at lower doses and were longer lasting than on bahiagrass. Suppression of seedheads was observed on both weed species, and for natalgrass this effect resulted in lower seedling densities in the following spring. Imazapic has excellent potential for selective control of natalgrass in stands of wiregrass on reclaimed lands in Florida. Bahiagrass control will likely require higher and perhaps repeated doses of imazapic, which may damage some native species. Caution is indicated when using imazapic on sites containing lopsided indiangrass.

MANAGING NUISANCE PLANT SPECIES IN FORESTED WETLANDS
ON RECLAIMED PHOSPHATE MINED LANDS IN FLORIDA

Paper presented at 26th Annual Conference on Ecosystems Restoration and Creation, Hillsborough Community College, Tampa, Florida. May, 1999.

Steven G. Richardson and Robert A. Kluson
Florida Institute of Phosphate Research, Bartow, Florida

Abstract: Florida regulations require that "nuisance" species, including the native primrose willow (Ludwigia peruviana) and cattail (Typha spp.), be limited to less than ten percent of the cover on reclaimed wetlands. Chemical and mechanical control of these species is expensive and may injure desirable trees and understory vegetation. It was hypothesized that shade-tolerant trees could compete with and shade out the shade-intolerant "nuisance" species. This study, conducted on reclaimed phosphate mined lands in central Florida, compared tree growth in the presence of primrose willow or cattail versus growth with these species removed (cut or herbicided). It also examined the effects of a developing tree canopy on primrose willow. The effects of elderberry (Sambucus canadensis) on tree growth were also studied. Growth of baldcypress (Taxodium distichum) was greater with primrose willow removal, but growth was substantial in the presence of primrose willow. Popash (Fraxinus caroliniana) and red maple (Acer rubrum) height growth was greater in the presence of primrose willow than when the primrose willow was removed by careful, directed application of triclopyr herbicide. In five or six years, 80 to 100% of the baldcypress, popash, red maple and water hickory (Carya aquatica) exceeded the height of the 2.3 to 2.7 m tall primrose willow. The developing canopy of the trees drastically reduced the leaf area index of primrose willow. About 80% of the baldcypress and pondcypress (Taxodium ascendens) trees grew taller than the 2 m tall cattail in seven years at one site, but popash did not compete as well with cattail at sites with standing water throughout the year. Baldcypress and popash grew as well in a planting of elderberry as in the weeded treatment. Costly control of primrose willow and cattail is probably not necessary in the reestablishment of forested wetlands in Florida if adapted trees are planted at sufficient density and site conditions allow vigorous tree growth.