Spring Tips for Your Water Garden

By Cindy Gilberg
St. Louis Gardener Magazine Spring 2002 issue

As the days of spring are warming up, gardeners everywhere watch in anticipation of those first signs that spring really has returned. It is no different in our water gardens. The hardy water lilies and marginal plants begin to sprout new growth. The fish begin to move about, providing color and movement. As in any garden, there are some spring maintenance activities that will insure success this year in your water garden.

Did you remember to trim back your water lilies and marginal plants in the autumn? If not, don’t fret. (Of course, hindsight is 20/20!) Look into the water to determine if there is a build-up of decaying leaves on the bottom of the pond. If so, this decaying material should be removed. A skimmer net will easily remove the larger leaves and debris. For the smaller debris, set up a siphon with a hose and ‘vacuum’ the bottom of your pond. (There are also commercially available Pond Vacs). Watch the other end of the hose in case you accidentally remove some of the smaller fish and frogs!

Spring is an excellent time to divide water lilies and marginal plants. Check to see if they are crowded and ‘jumping out’ over the edge of their planting containers. The marginal plants are generally divided the same as one would divide regular perennials, cutting the crown into fist-sized pieces that contain both some crown and healthy roots. Repot the divisions into new containers with aquatic soil or topsoil, aquatic plant fertilizer tablets and top with pea gravel.

When dividing water lilies, first unpot the plant and rinse off all the soil so you can better see where to cut. Cut the thizomes into 3”-6” pieces that each contains a healthy ‘eye’ or growing tip. Repot the rhizome pieces the same as above so that the crown is at the soil surface (not buried).

It is very helpful, with both existing water lilies and newly planted divisions, to set the containers so that they are in shallow water with about 5”-6” of water covering the crowns of the plants. The shallow water warms faster and encourages early growth on the lilies. As they begin to put on good growth, they can be gradually moved into the deeper water.

Throughout the spring and summer remove any yellowing or dead leaves to prevent a buildup of debris on the bottom of the pond. Continue to add aquatic plant fertilizer tablets to the water lilies and other water plants in summer according to the label recommendations. Some fertilizers are longer term slow-release formulas and won’t need to be reapplied as often.

Check the water level in the pond. When adding new water, always dechlorinate the water as you add it if there is chlorine present in your water supply. It is helpful to drain about 20% of the volume of the pond and replace it with fresh water to eliminate any excess gases that may have built up over the winter. This can be done at the same time as the ‘vacuuming’ of the bottom of the pond. Don’t be tempted to completely drain and clean the pond – this is done only in the case of emergency situations. The pH of the water should also be tested. For healthy plants and fish, the optimum pH is 6.5 to 7.0. Water that has a higher pH can cause excessive algal growth and a general decline in the health of fish and plants.

If you use a pump, now is the time to bring it out of storage and place it in the pond. As the water begins to warm up, the extra aeration will be needed. Check your filter to see if it needs a spring cleaning and replace the filter media if necessary. When the water temperature has reached about 65 to 70 degrees, pour a solution of beneficial bacteria (available commercially) onto the filter media to refresh the biological activity of your filter. It is normal to see some algal growth in the spring as the water warms up. This is due to the fact that the simple-celled algae grow much faster than your water plants. It will take a few weeks for a balance to be achieved and for the water clarity to improve. By aerating the water and regularly dosing the filter material with a solution of beneficial bacteria, algae problems can be kept at a minimum.

Don’t be tempted to overfeed the fish as they begin to be active, no matter how much they seem to ‘beg’. Overfeeding, especially at lower temperatures, can cause water quality problems. There are spring and autumn formula fish foods available that will help alleviate this problem. Be sure to feed small amounts until the water temperature reaches about 65 to 70 degrees. Fish will occasionally feed on plants that are set into the pond, somehow always going for the most expensive of water lilies. If this becomes a consistent problem, the plants should be protected. Protective plant nets are commercially available and effective.

Here are a few “rules of thumb” for a water garden that will help to maintain a natural balance and good water quality:

• For every square foot of water surface area in your pond, you want approximately 1” of fish length and three bundles of underwater oxygenating plants. Overcrowding with fish will increase the nutrients in the water and thus increase the amount of algae that grows. The oxygenating plants will efficiently out-compete the algae for nutrients.
• Floating plants or foliage (such as water lily pads) should cover 50% of your pond’s surface to allow the fish shelter from the sun, to keep the water temperature lower and to effectively compete with potential algal growth.
• Redose your water garden with a beneficial bacterial solution at intervals and concentrations as stated on the label.
  Regularly monitor the pH of the water – remember that the optimal pH is 6.5 to 7.0.

Now that you have taken care of a bit of spring maintenance in your water garden, just sit back and enjoy your own backyard oasis.

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