Aldrovanda vesiculosa CULTURAL INFORMATION Planting Media
The plants require an acid water pH 6-6.9. Place at least 2 inches of garden, swamp or woodland soil or sphagnum peat moss in the bottom of the container which must be deep enough to provide the plant with a water depth of 6-12 in. (15-30 cm). If sphagnum peat moss is used, the moss will float for about a week until it becomes thoroughly wet and settles to the bottom of the container. (Strain the floating debris from the surface after the moss has sunk.)
After the water has cleared, check the acidity or pH with a pH meter or test paper. Kits for measuring pH are available from tropical fish stores. You do not need the whole kit, just the chemical bromthymol blue which is used as follows. Add 3 drops ol bromthymol blue to 2 tablespoons (30 ml) of water. If the color of the water changes to yellow it is too acid, if the water turns blue the water is sweet or alkaline and if it turns green, it is just right. If the water is too acid, add a very small quantity of a base such calcium oxide, calcium hydroxide, baking soda or sodium biphosphate. Wait a few hours and then check the pH again. Continue adding the base and checking the results until the desired pH is achieved. If pH is too high, that is, it is alkaline, add acid in the form of dilute sulfuric acid, citric acid, tannic acid, or acetic acid (vinegar) in small quantities until the correct pH is achieved. Some growers lower the pH by adding chopped straw, grasses, sedges, cattails, and pine or fir or spruce needles. A general rule is to add k cup (60 ml) of such plant material per gallon of water. In a few days the wate r will turn yellowish brown.
Another technique is to soak sphagnum peat moss in water for a few days. Drain off the water and add it to the Aldrovanda water.
Irises (7ns), rushes (Juncus), reeds (Phragmites), arrowhead (Sagittaria), and cattails (Typha) grown in the same container condition the water for improved growth and flowering of Aldrovanda. Water color should be yellowish like beer or urine. If the water turns black, change it at once and review cultural conditions to prevent reoccurrence. The water should not all be replaced at one time in order to maintain a proper pH. Replace some each day or so with fresh water until the water has regained a yellowish color.
Aldrovanda plants grow in the tropic and temperate regions of the world. In some temperate regions the plants are subjected to freezing temperatures. Under our growing conditions the plants produce winter buds at temperatures below 50°F (10°C). We over-winter our plants at a temperature of 35°F (2°C). We maintain summer temperatures (growing season) in the 70-86°F (21-30°C) range.
In temperate regions Aldrovanda plants go into dormancy and form winter buds which settle to the bottom of the water until conditions are suitable for growth. In tropical areas the plants are evergreen and grow the year around. Therefore, they do not form winter buds.
Aldrovanda is accustomed to and requires strong light for vigorous growth. The plants can utilize several hours of direct sunlight as long as the water temperature does not exceed about 86°F (30°C). Growth is poor above this temperature. If the plants are
Fig. 6-12 Aldrovanda trap with inward pointing spokes which intermesh upon closure. Sequence of closure is from left to right. Final closure, the narrowing phase is induced by struggling prey.
growing in a container with transparent walls and placed in direct sunlight, the sides of the container should be covered with white opaque materials to prevent sunlight from overheating the water.
Direct sunlight tends to encourage algae growth, particularly if the water is not sufficiently acid. Algae growth inhibits Aldrovanda growth.
A grower reports that a product called Acurel E, available from Lilyponds Water-Gardens, Lilyponds, MD 21717 U.S.A., will kill the algae without harming Aldrovanda. Four drops per gallon of water is sufficient. He advises that the water may turn purple but will soon clear.
Artificial light — 1500 foot candles during growing season. Very little light is needed during dormancy. Photoperiod 14-16 hours during the growing period and 6-10 hours during dormancy.
Adding fertilizer to the water for these plants is usually not advised as the fertilizer induces algae growth. Add very small water animals such as daphnia, water spiders, and micro worms to feed the plants. See Chapter 7 for directions. Miscellaneous
A few snails added to the water in a glass container will keep the glass walls clean. Some growers use aerators to bubble air through the water.
When the plants have elongated and branched out so that the surface of the water is occupied, further growth will be inhibited. In this case transfer the plant to a larger container or divide it and place parts of it in other containers.
If the cultural environment is excellent the terminal bud will be spherical and plump.
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