MASTER GARDENER: Propagating plumeria cuttings, controlling hydrangea color

MASTER GARDENER: Propagating plumeria cuttings, controlling hydrangea color

Q. I have loved plumerias since I first saw them in Hawaii and brought home a few cuttings. My question is: Some of the plants I have were inherited, were not well cared for, and are extremely 'leggy'. Can I cut some of the branches and re-root them? I wouldn't mind sacrificing the 'mother plant' if it meant getting several off-spring and hopefully fuller plants. Please advise if this is possible, the best time to take the cuttings and the procedure for doing it.

A. The plumeria, Plumeria rubra, is a beautiful shrub or small tree that has colorful, exceptionally fragrant flowers. Although it is considered a tropical plant, it seems to grow very well outdoors in Southern California, whether planted in a pot or in the ground, as long as it is protected from hard frosts. Although the plumeria is usually a rather expensive plant to buy, it is a surprisingly easy plant to propagate from cuttings.

Plumeria cuttings will root best when the temperature is at least 60 degrees, so spring is a good time to start making your cuttings. Simply cut piece of a branch 12-18 inches long. The cutting may be a single length or branched, with the branched cuttings likely to make the bushiest plants. You will find that a milky sap will immediately start dripping from the cut surfaces. Avoid getting the sap on your skin as some people are sensitive to it and may develop a rash. Allow the cut ends of the branches to dry in a cool shady location for at least a few days. This drying time drastically reduces the chance of rot occurring.

Remove all but the top few small leaves from the cuttings (they will drop off eventually anyway). If you are making multiple cuttings from one very long branch, then be sure to keep track of which end is up. Plant each cutting about three inches deep in a one-gallon or larger pot filled with an artificial soil mix that will drain quickly. A general-purpose mix with almost an equal volume of perlite or vermiculite works well for me. There is no need to use a rooting hormone. Place the pots in a bright location but avoid direct sun, and keep the soil moist but not soggy. Depending upon the time of year, rooting will take one to three months. Once the cuttings develop roots you will notice top growth beginning, and you can gradually move the new plants to a location with brighter light and increase watering.

Dont fertilize during the fall and winter to avoid promoting tender growth that could be damaged by cold weather. During the first winter, the young plants may require more protection from frost than the parent plant. Regardless of age, plumerias require little water during the winter; give them just enough to keep the branches from shriveling. When spring arrives, begin fertilization and increase watering. Before long, the colorful, fragrant flowers of the new plumeria plants will be ready to fill your garden with color and fragrance.

Q. Several years ago you told how to control the color on hydrangeas, but I've forgotten how to do it. Would you repeat the instructions?

A. The color of the hydrangea will vary according to the pH of the soil in which it is growing. Blue flowers are produced by adding aluminum sulfate to the soil to make the soil more acidic. Pink flowers can be assured by a heavy application of superphosphate to the soil to make the soil more alkaline. Either treatment must be begun well ahead of the blooming season to be effective so as soon as you notice spring growth, you should begin application. In our Southern California soils, untreated hydrangeas are likely to be pink, unless the soil is treated to produce blue flowers.

Ottillia Toots Bier has been a UC Cooperative Extension master gardener since 1980. Send comments and questions to features@pe.com.

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MASTER GARDENER: Propagating plumeria cuttings, controlling hydrangea color