Written by Ann Lambrecht
In this column I will try to cover different types of vegetative reproduction of aquatic plants. I will include diagrams (not included in this) when it will help make something more clear.
Lets start by covering propagation by runners. These runners appear at the leaf axil of plants, such as, all Vallisneria, a group of Echinodorus species, almost all Cryptocorynes, and many Sagittaria. These runners grow horizontally along or just below the surface of the substratum (gravel bed) of the aquarium. The runners will put up small plants or slips at regular intervals along its length. When these plantlets are well rooted they may be separated from the mother plant by severing the runner shoot. Once the runner has been cut it will cease to produce new plants. Some species of floating plants, when anchored in the substrates in shallow water, will produce runners as well. These include Eichornia crassipes (Water Hyacinth), Pistia stratiotes (Water Lettuce), Stratiotes aloides, Hydrocharis morsus-ranae, and species of Limnobium. These are very good pool or bog plants, but are usually short-lived in the aquarium.
Now on the method of propagation rarely used by mother nature, cuttings. This is an excellent method for any plant capable of the production of adventitious roots. Some of these are Hygrophila, Ludwiqia, Cabomba, Limnophila, Cardanine, Bacopa, Hottonia, Myriophyllum, and Ceratophyllum to name just a few. Propagation by cuttings is the most common way of increasing aquatic plants. The amount of cuttings depends on the size of the mother plant. Be sure to leave at least two sets of leaf nodes on the mother plant to assure continued growth. This will come in the form of axillary shoots. The first cutting taken is called a head cutting and contains the apical bud and will be then first to show new growth. If the stem is long enough further cuttings may be taken. Be sure you have a minimum of two leaf nodes for every cutting and left on the base (mother plant). These cuttings are called shoot or stem cuttings. These should have at least three leaf nodes in my opinion as they must produce roots and axillary shoots. I use my fingers to obtain cuttings, as most of these plants have soft stems. Be sure and handle your cuttings gently as bruising or crushing will cause your cutting to rot. Now you need to remove all the leaves from the bottom nodes that are going to be under the gravel as they will rot and can cause stem rot. Your new roots will appear on these nodes.