Perfect Days for Gardening

Our exceptionally pleasant fall weather continues. The low humidity has led to the need for some irrigation, but we will gladly buy the water in exchange for less mugginess. Already I am harvesting baby arugula, along with Sugar Snap peas, the last of the leeks and okra. The bak choy is coming on strong, and we will be able to pick a few leaves of kale within another week or so.

This weekend I planted out lettuce, cilantro, scallions and spinach that were started in cell trays September 7th. With rain on the way, the timing should be perfect. Mache growing in the greenhouse will soon be ready to transplant. I start the seeds in a 6 X 30 planter and transplant to thin them. The ones left behind in the planter will mature about ten days earlier than the transplants, extending the harvest to a month or so.

Many people do not transplant spinach, direct sowing instead. I find we get a bigger harvest with less work when we transplant and give the plants growing space. Japanese spinach farmers employ this technique.

We have been amazed at the productivity of the pond. In this year's experiment, we stocked two dozen immature tropical livebearers for mosquito control. By summer's end, we had harvested roughly 500 fish, which were sold to a local aquarium store as "feeders," for predatory pet fish. We moved 7 of the prettiest ones to a small aquarium where they will spend the winter and provide stock for next spring.

We have little interest in food fish, not wanting to have the trouble of cleaning them and dealing with wastes. Nevertheless, it is clear that even a small garden pond could theoretically supply some additional protein. Others who, like us, would prefer to sell live fish rather than dead ones, have the option of producing a small income from the pond by cultivating and harvesting smaller, tropical species. The key to this, of course, is finding an aquarium shop that wants to purchase your stock.

Next season, we intend to construct a growing bed that will filter the pond while providing space for additional crop production. This form of hydroponic growing, known as "aquaponics," uses the fish wastes to fertilize organic vegetables growing in an inert medium. Most of these culture systems rely on inputs of prepared fish foods and operate under the protection of a greenhouse room. Our interest lies in creating systems that can function year round in the local climate zone, with minimal inputs of fish food. By planting flowers and other plants around the pond and providing a diverse community of aquatic and semi-aquatic plants, it should be possible for the system to produce enough algae and insects to feed the fish. Stay tuned.

Garden Pond a Study in Ecology

One of the best things we have done in the garden in years is add a pond. We have actually been working in this direction for about five years. Originally, we removed a tree. Then we removed the stump, and were left with a large hole in the ground. We decided to make it larger rather than fill it up, and eventually we wound up with a pond.

Watching our pond develop its own little ecosystem has been both fun and instructive. We began in February, as soon as the weather began giving us a few warm, bright days, by adding a commercial bacterial starter culture to seed the pond with beneficial bacteria. This technique is much like adding a bacterial product to your compost, or putting nitrogen-fixing bacteria into a row with bean seeds. You are giving Nature a head start on ecosystem development. Left to its own devices, the pond will acquire these essential micro-organisms. They will drift in on air currents, on the feet and feathers of birds and on the bodies of insects that happen to visit the pond. Adding the commercial product simply speeds up this process.

Within a week, the pond became cloudy, teeming with microscopic life. Besides the added bacteria, the water was full of microscopic algae that tinted everything greenish brown. During the first month, the water was alternately cloudy and clear, as vast numbers of organisms grew and died, each subtly altering the water conditions and contributing to the pond's ecology.

By the end of March, we had added some marginal plants. Marsh marigold (Caltha palustris) was the first flowering plant to go into the new pond. Our plant came originally from a friend in Michigan, and it has lived in various ponds and containers for almost 25 years. Next we added Iris virginica, the native blue flag. Our plants are tetraploid ones, originally from Barry Glick at Sunshine Farm and Gardens. During early spring, we added several other species that like wet feet, including cinnamon and royal ferns (Osmunda cinnamonea, and O. regalis), dwarf cattail (Typha minima), blue moneywort (Lindernia grandiflora) and four-leaf-clover (Marsilea quadrifolia).

This week, we added our first water lily, Nymphaea aquatica 'Charley's Choice.' This cultivar remains under three feet in diameter, making it a good choice for a small pond such as ours. The pink and white blossoms open during the daylight hours.

We have also added fish. While we would prefer to have native Tennessee fishes in the pond, it is illegal to maintain native fish species in captivity without a permit, so we have opted for goldfish and livebearers from Aquarium Knoxville, our local pond supply store. The goldfish is a Shubunkin type, bred for coloration that shows up well when the fish is observed from above. We have only one spcecimen, whom we have named "Ichiban." With 1200 gallons of water, the pond can support only a limited number of fish. Because goldfish can reproduce prodigiously after a couple of years in the pond, we decided to keep only one. If we added more and happened to end up with a pair, we would need to periodically net out many hundreds of offspring. Finding a home for unwanted fishes is even harder than trying to place a litter of kittens. And unfortunately, there is no way to determine the gender of small goldfish. Ichiban, therefore, will remain celibate.

To help Ichiban with mosquito control (the primary purpose of having pond fish in the first place) we added a couple of dozen small mixed livebearers from Aquarium. They sell these to feed larger fish, and they are therefore quite cheap. Further, they will bear offspring about every three weeks, ensuring a continuously growing population all season long. Livebearers are also not winter hardy in Tennessee's climate, sparing us the need to cull them at season's end.

While it is true that the decisions Jerry and I make regarding the pond's inhabitants have an effect on its development, many of its most interesting denizens arrived on their own. Certainly this was the case with the micro-organisms that were not in the bottle of bacterial starter. In terms of diversity of species, one look with a microscope will reveal that this part of the pond's ecology is the hands-down leader. Next came the insects. Even while the nights were still a bit frosty, midges arrived in hordes, and their aquatic larvae were soon teeming on the bottom of the pond, hiding themselves in little tubes they construct from debris. Next to show up were the water striders, accomplished hunters who sit delicately poised on the surface to await another insect's misfortune. As soon as anything alive falls into the water, the striders head for it, hoping to make a meal of a struggling fly or moth. A little later, backswimmers arrived. They also hunt for prey at the water surface, but with a different strategy. The backswimmer lies upside down (hence the name) just beneath the surface, rather than floating supported by surface tension. This appears to confer the advantage of speed, as the backswimmers can move faster than water striders can. The last insect arrivals have been the elegant dragonflies and damselflies. The blue dasher (Pachydiplax longipennis) has been the most common species so far. Males spend most of their time defending territories from each other, awaiting the arrival of a female with which to mate. I have observed the females depositing eggs within a few moments after a mating flight. Dragonfly larvae are aquatic predators, while adults hunt other insects on the wing. We have seen a damselfly, probably an Enallagma species, together with two other dragonflies, one is a member of the darner family, the other is a common whitetail, Plathemis lydia. The latter is unmistakable, with its powder white abdomen and boldly marked wings. Both of these dragonflies have been occasional visitors, whereas the dashers seem to have taken up residence.

We also have at least two species of frogs. One is the common leopard frog. We also have a smaller chorus frog and possibly a tree frog species. All the frogs found the pond on their own, possibly moving from one of the small creeks that surround the base of our ridge.

Within only a few months, our pond has gone from being a hole in the ground to a thriving community that never fails to provide entertainment and insight.

Edible Pond Plants

As we continue to plan our garden pond, we have noted that many aquatic and semi-aquatic plants are edible or have edible parts.

Edible Sagittaria also sports atrtractive blooms.

Lotus root, for example, is available in Asian groceries. Although most lotus grow too large for a backyard pond, there are dwarf varieties with stunning large flowers. Like water lilies, they are vigorous, and need dividing periodically. Roots, therefore, will be available for stir fries. Arrowhead (Sagittaria latifolia) is sometimes called “duck potato” because of its edible rootstock. The young leaves and seeds of pickerel rush (Pontederia cordata) can be added to salads, as can duckweed (Lemna minor). Cattail (Typha species) spring shoots and pollen are edible, too. Celery is among the more common vegetables that can be grown in bog conditions. Water chestnut, water spinach, and watercress are all possibilities, too. A few water herbs, for example Bacopa caroliniana and Hottuynia cordata, are used like lemon balm and cilantro, respectively. Mint, of course, is famously vigorous in marshy conditions. Plant with care.

Indeed, this could be said of all water garden plants. If the pond is located in full sun, they can be amazingly productive. Most water gardens need an annual renovation to avoid looking overgrown. Certainly, every three years in all but the largest ponds, it will be necessary to reduce the plant population.

Fish, too, can become overcrowded in a garden pond. Goldfish, the recommended variety for beginning water gardeners, often produce offspring after they are over six inches in length. These can number in the hundreds, and only a few of them will bear the bright coloration of their parents. It is advisable, therefore, to thin the herd on a regular basis. Ponds under 5000 gallons may need this every 5 years.

It is worth mentioning that we have considered the possibility of raising food fish. We rejected this idea because the pond is too small to accommodate a reasonable number of winter hardy fish. (The typical home aquaculture set-up is focused on Tilapia, a tropical fish.) While we could certainly add a few bluegills and/or catfish, the effort would hardly be justified by the meager harvest we could expect. Pond fishery managers tend to think in terms of pounds per acre, not per square foot. Besides, the only way to catch them without disrupting the plantings would be on hook and line. We will probably stock the pond with local fish rather than goldfish, but not for eating. We would emphasize that every garden pond should be home to a few fish for purposes of mosquito control. Otherwise, the pond will require regular treatment for the pesky insects.

A lot of planning has already gone into our pond project, and we have more work to do. We will post updates and images as we have them. It will be next spring before we begin planting, and next summer before the fish will arrive.