D. Joseph Eakes, Gary J. Keever, Charles H. Gilliam, and Penelope A. Merritt

As the value and function of wetlands become better understood, national policies are being developed requiring wetland preservation and restoration. In the past, most plants used for the purpose of wetland mitigation and restoration were harvested from native stands. Commercial production of these plants would prevent unnecessary environmental degradation. Along with the movement to maintain and restore wetlands, the popularity of water gardening in home and commercial landscapes has increased. Nursery owners have an opportunity to take advantage of this growing market by contract production of wetland plants and/or the production of ornamental wetland/aquatic plants for the landscape.

Although extensive research covering culture of typical woody and herbaceous container-grown plant production is available, there is little literature concerning container production of wetland plants. The objective of this work was to determine the effects of container hole position on the production of four wetland plant species.

METHODS
On May 23, four wetland species—canna, iris, smooth cordgrass, and soft stem rush—were planted into trade gallon containers of Metro Mix 500. The five container types used were (1) no holes, (2) four holes located at the bottom of the container, (3) four holes half way (3.2 inches) up the container side wall, (4) four holes three-quarters of the way (4.7 inches) up the container side wall, and (5) pot-in-pot which consisted of a trade gallon pot with four holes at the bottom placed in a full gallon socket pot lined with poly. All plants were fertilized with two Sierra (18-6-12 plus minor nutrients) tablets (2.39 grams of nitrogen) per pot placed just below each transplant. Plants were watered to 100% container capacity daily, and grown in a double wall poly greenhouse at a minimum set temperature of 65^oF.

Plant growth index [(height + width1 + width2 )/3 where width1 is at the widest point, and width2 is perpendicular to width1], total shoot number (or leaf number of soft rush), visual shoot rating (a scale of 0 - 5 with 0 being dead and 5 being a large, healthy plant), and medium solution pH and soluble salt concentration were determined 60 days after potting (DAP) for each plant. Due to the rapid growth of canna, visual root ratings and shoot dry weights were also determined 60 DAP. At 90 DAP growth indices, total shoot numbers, and root and shoot visual ratings were determined for iris, rush, and smooth cordgrass. Plants were then harvested to determine shoot dry weights.

RESULTS
Growth indices for canna 60 DAP were greater for pot-in-pot plants and plants produced in pots with holes half way up the container side walls (Table 1). Plants produced in containers with holes three-fourths of the way up the container side wall had the lowest growth indices. Plants in the pot-in-pot containers had the highest visual shoot dry weights and plants produced in traditional containers with holes at the bottom had the lowest shoot dry weights. Visual root and shoot ratings for canna were highest for plants in the pot-in-pot treatment. Visual ratings were similar for cannas in all other treatments. Soft stem rush grown in the pot-in-pot treatment had higher growth indices, higher leaf and root ratings, and greater shoot dry weights than plants grown in the other four pot types (Table 2). There were no treatment differences with any growth parameters for smooth cordgrass or iris.

Although medium solution pH and soluble salt ranges varied among species, treatment differences were similar. Lower soluble salts and higher pH levels were observed in pot-in-pot medium solution samples compared to samples from the other pot types. Medium solution pH averaged 5.7 for pot-in-pot soft stem rush while the remaining four pot treatments averaged 5.0 and ranged from 4.6 to 5.3. Soluble salt levels in pots with no holes, holes half way up the container side wall, and holes three-quarters up the container side wall ranged from 4.0 to 5.5 dS/m, while salt levels in containers with holes at the bottom and pot-in-pot containers averaged 0.5 dS/m.

In summary, canna and soft stem rush grown in a pot-in-pot system were larger, higher quality, more marketable plants than those grown in conventional containers regardless of drain hole position.