Garden Mastery Tips
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May 2005 |
Colorful Coleus
Native to Indonesia and Malaysia, Coleus are tropical tender perennials that have been popular foliage plants since Victorian times. Dutch traders carried several species to Europe in the mid-1800s and immediately, plant breeders began to hybridize them. They have created over the years a very large number of vegetatively propagated strains with an almost infinite number of leaf color combinations including most colors of the spectrum except true blue. Hybrids range in size from dwarf 6" tall plants to large mounded 36" tall plants. They are members of the Lamiacea (mint) family and therefore, have four-sided stems which are semi-succulent. Blue to white nettle-like flowers (more common on seed strains) bloom in racemes in summer, but are not showy and tend to visually detract from the symmetry and attractiveness of the plant leaves. Leaves frequently feature mixtures of colors in irregular patterns and are ovate to oblong and toothed.
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Until recently, Coleus have been reserved for use as houseplants or to brighten a shady corner in the garden. When grown in the sun, their colors tended to fade. Also, when the summer days are longer than nights, Coleus start to send up bloom stalks, and they go on and on producing flower stalks for the rest of the summer, until frost or until the tired gardener gives up pinching them out. But good news, in the 1990s Dr. Allan Armitage of the University of Georgia introduced a series of new cultivars that were vegetatively propagated, with very few flower stalks. These new cultivars were also selected for their ability to stay brightly colored in sun or shade. They thrive best in warm spots, sunny or shady, in moist, rich, well-drained soil.
Coleus Problems
If you find yellow stippling on the leaves of your Coleus, it's probably a sign of mites. As soon as you notice the first stippling of the leaves, spray your Coleus plants early in the morning with a forceful stream of water to knock mites from the leaf undersides. Spraying in the morning allows the leaves time to dry out during the day. Repeat daily for three days.
Small plants that display poor coloring may be infested with whiteflies. Look for these tiny, white-winged, moth-like insects on the undersides of leaves. Control whiteflies by spraying infested plants with an insecticidal soap every three to five days for two weeks.
Older plants tend to become leggy. If your plants are spindly, pinch out the top center stem and a few side ones. This will encourage the plant to grow thicker and bushier.
Root rot occurs when there is insufficient drainage. Amend soil for better aeration.
Enhance Coleus colors by spraying the plants with seaweed extract in late spring and once again in early summer.
If the foliage on older plants begins to fade, consider taking cuttings. The new plants will perform better.
Propagating Coleus
Expanding your Coleus collection is quite easy. Seeds are inexpensive, readily available and can be sprouted and showing their first colors in as little as two weeks. An advantage to growing Coleus from seed is that most seed packets will contain many different colors. From this variety you can choose your favorites to propagate for the future, by taking cuttings.
Coleus seeds are very small and should be sown onto a layer of moistened, sterile potting soil in a shallow tray, and then covered with a thin layer of fine soil. The tray should then be covered with a sheet of clear plastic to retain moisture, until the seeds have sprouted. Keep the tray in a warm (65-75 degree F), bright place. When the seedlings are large enough to handle easily, they should be thinned out and transplanted into individual pots. When all danger of frost is past the plants may be set out in the garden.
Propagating your Coleus by cuttings is equally easy. Take cuttings in the fall, prior to frost, and grow your Coleus as a house plant to brighten the winter months. In February or March, again take several cuttings and cultivate them for transplant into the garden or container when the weather warms. Coleus plants should not be set into the landscape until the minimum outdoor temperature is 50 degrees F. Feed monthly with a 10-10-10 fertilizer.
Here's how to do it:
When the temperature is above 60 degrees F, take terminal cuttings (the tops of actively growing stems) that are about 3 inches long and have two or three "nodes," or buds that will open into new leaves. Trim the cutting flush to the bottom node.
Remove all but the top two sets of leaves. If the second set is quite large, they can be cut in half.
Place the cuttings in a tray filled with soil-less mix, such as a moist 3-to-1 ratio of perlite to peat, or straight perlite. Cover the container with a plastic bag to maintain moisture and place it in a warm area (70 to 75 degrees F). The warmer the temperature, the faster the rooting process. It is not necessary to use a rooting hormone. They will also root quickly when set in moist sand or vermiculite, or even in a glass of room temperature tap water.
Roots will sprout within 10 days, and a well-rooted plant is ready for transplanting to your garden after 2 to 3 weeks.
For some beautiful photographs of Coleus go to:
http://Coleusfinder.org
http://www.glasshouseworks.com/gallery2.html
References
http://www.thegardenhelper.com/coleus.html
http://www.gardenguides.com/articles/coleus.htm Marshen, Georgiana. Coleus- Out of the Shadows and Into the Light. August 2000
http://hgic.clemson.edu/factsheets/HGIC1162.htm
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