Find a passionate gardener and you'll likely find a jar of cuttings rooting on a windowsill. Rooting plants in water is one of the most time-honored methods of propagation and one of the easiest. Water propagation isn't quite as simple as sticking the cutting in water and forgetting it, and not all plants can be rooted in water. Many that can, have become favorite pass-along plants due to the ease of multiplying them -- not to mention the pleasure of giving them away.
Plants root better in distilled or rain water. The lack of chemicals keeps algae from forming inside the container. Using tap water is fine, but you will need to change the water every other day to keep your cuttings healthy. Clear glass is preferable to dark, colored or opaque glass. Plastic can be used, but algae seems to grow faster in plastic and build up on the inside container walls.
Trees and Shrubs
The best way to know if a tree cutting will root in water is to check for little bumps or nodes on the softwood branches, although not all will have them. Trees that are known to root in water include rose of Sharon , elderberry, avocado, loquat, ficus and willow. Shrubs include hibiscus, pussy willow, butterfly bush, gardenia, oleander, boxwood, croton, viburnum, plumbago, jasmine, ixora, jatropha and flowering maple. Some shrubs, such as hibiscus, jatropha and flowering maple, can be trained into small trees.
Annuals and Perennials
What is annual or perennial largely depends on your U.S. Department of Agriculture growing zone. For example, a geranium can live for many seasons in zone 9, but is an annual in zones 8 and below. Rooting cuttings is one way to keep a plant going over the winter indoors. Some annuals and perennials whose cuttings can be rooted in water include coleus, impatiens, lantana, brugmansia, ruellia, kalanchoe, sedum, shrimp plant, salvia, sage, lavender, fuschia, geranium, marigolds, dianthus, balloon plant, obedient plant, penta and forget-me-not.
There are flowering and non-flowering vines that can be propagated in water. These include passion vine, clematis, ornamental sweet potato, ivy, dutchman's pipe, bleeding heart, confederate jasmine, mandevilla and stephanotis. When rooting vines, it is best to submerge at least three nodes under water.
Vegetables and Herbs
While not many vegetables can be rooted in water, there are a few, including tomatoes, sweet potato vines and peppers. Herbs that will root in water include mint, basil, sage, dill, oregano and rosemary.