Mountain Pond Care
By Ken Lain, The Garden Guy

According to television and radio commercials the holiday shopping season is well under way, and activity at the garden center is in keeping with this premise. This week I confirmed my cut Christmas tree order and our annual Christmas shop officially opened. As usual, the shop’s displays are receiving rave reviews, and for this, as usual, the credit goes to my wife, Lisa, and her staff of designers. Their outstanding flare for holiday design deserves a hearty, "Well done"!

If you have a pond in your garden, all this holiday preparation is your cue to prepare that pond for its winter nap. Yes, it’s time to start thinking of winter maintenance for water gardens. A mild winter is predicted which is good news for pond owners because getting ready for an easy winter requires less work than preparing for a hard one. As winter approaches and water plants show off their fall colors, there are a few precautions that will keep plants and fish healthy during the cold months.

Most water plants are perennials. Each winter their foliage dies back to the roots and reemerges the following spring. When the foliage of lilies and shallower bog plants is no longer green, cut back the plants and place the containers at the bottom of the pond, in the 2- to 4-foot level. This will better insulate the roots from freezing. Tropical water lilies, however, must be taken indoors or wintered in a well-lit garage and kept moist. I find that many pond owners treat tropical lilies like annuals. They just let them die and replace ‘em next spring.

Goldfish and koi will be fine through the winter. As the water temperature dips close to freezing, fish will no longer need to be fed. Their metabolisms shut down and they hibernate, requiring little to no food throughout the winter. However, since dormant plants will leave fish exposed to predators, make sure that your pond’s finned residents have places to hide from hungry raccoons and blue herons.

As the water temperature dips below 50 degrees, turtles, like our red-eared sliders, need to be brought indoors for hibernation. If not, they tend to wander off to hibernate in the ground and rarely return the following spring. Because our girls really are fond of them, I just brought our turtles indoors for their winter sleep.

The most important thing you can do for plants and fish that winter in the pond is keep the water surface from freezing into a solid mass, something that occasionally happens in January. A portion of the water’s surface must always remain open to the air, allowing life-sustaining oxygen to enter the pond.

There are several ways to keep a pond’s surface open. The easiest is to keep the water running. Even the slightest movement at the water’s surface will do the trick. Of course, waterfalls prevent freezing but you also can keep the surface open by floating a couple of tennis balls or a piece of lumber in the water. The sun warms these floating objects and their residual warmth keeps the water from freezing.

De-icers and pond heaters also do the job. These float on the surface and agitate the water to prevent a suffocating ice cover. They use very little energy because most are designed with thermostats that only activate when water temperature approaches 32 degrees. A small recirculating pump pointed straight up at the water’s surface will draw oxygen back into the water, too.

Fall in the mountains presents a spectacular show of leaf color, but the subsequent leaf drop can be a problem for ponds. Leaves should be removed before they settle and accumulate at the bottom of the pond. Debris deeper than two inches on the bottom will decompose and turn to deadly winter gasses that can kill pond fish and plants.
Bird netting used to keep birds out of fruit trees works great at keeping leaves out of ponds. Just stretch the netting across the pond and fasten securely with landscape fabric pins. The black plastic netting blends into the surface of the pond and is hardly visible. Even if most of the leaves already have dropped, the netting will keep out blowing leaves. This same bird netting will keep blue heron and raccoons form eating the fish and plants as well, so it provides a double benefit to your pond.

A pond’s last algae bloom of the year will turn the water thick and green. To keep the pond in balance the water must be kept blue. Garden centers sell blue dye that is organic and safe for plants and fish, but serves to keep your pond clear. I recommend adding this blue shading color to the pond as soon as the last lily leaf drops.

Until next week, I’ll see you in the garden center.

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