By Denise Seghesio Levine, U.C. Master Gardener of Napa County
A seed packet of Rainbow Floral Strain Mix of coleus is on my table and that is pretty exciting. Better than a box of mixed chocolates, this non-caloric envelope of a potential rainbow of eye candy is waiting to be sown and nurtured. Living foliage kaleidoscopes will be my winter color project.
Coleus (Plectranthus scutellarioides) is actually a member of the mint and dead nettle family. As I look at the shape and texture of the leaves, I can see the resemblance.
Coleus is considered a shade plant, but many darker colors can handle some sun and some varieties are very happy in bright light. Varieties that like sun are called sun coleus and include Premium Sun Crimson Gold, Lime Delight and Chocolate Symphony.
I recently returned from a trip to Louisiana where coleus in lime green, lemon yellow, flamingo pink and chocolate brown in wonderfully varied heights and shapes tumbled over each other in lush beds. They grew in bright, steamy sunlight throughout most of the day.
I do not know if coleus make it through the entire year in Louisiana, but in Napa Valley, coleus should be grown as an annual or dug up when temperatures get cold and brought inside to grow as a houseplant. In protected areas and some of Napa Valley's banana belts, coleus may survive winter outdoors.
You will get the most vibrant color from coleus that receive morning sun and afternoon shade, but there are coleus choices for most light conditions. While most coleus like shade, too much shade can cause plants to become weak and spindly.
Coleus are easy to propagate from cuttings, but I like the grab-bag surprise of planting from mixed seed and seeing what I get. Coleus seeds need light and warmth to germinate. Sow seeds on top of damp soil or seed starting mix, press them gently into the soil and do not cover.
Place the pots on a heating pad, seed-starting mat or cozy window sill to get them started and keep between 70ºF and 75ºF. When your plants get two real leaves, gently transplant them into their own little pots if they are not in individual cells. As plants develop multiple leaves and branches, pinch them right above a branching junction to shape and stimulate growth. Transplant to larger containers as needed.
When I read reviews from other gardeners who have sown these seeds, it seems that one of the hardest tasks is deciding which seedlings to thin out when all the colors and patterns are so enticing. Planting individual seeds in their own cells eliminates the need to toss fragile thinnings.
Put plants near a sunny window for the winter or plug in grow lights if natural light is scarce. Cut coleus back when they begin to bloom to keep them compact. Leaving flowers depletes the energy of the plant, and besides, the foliage is the tar, not the flowers.
If you want to grow coleus outside, grow them through the winter as houseplants or in the greenhouse, harden them off and gradually get them used to outside temperatures. Transplant when the danger of frost is past and nighttime temperature are in the high 50s and 60s.
Coleus grown outdoors enjoy the same conditions as begonias and impatiens.
Because coleus like water and frequent watering can leach nutrients, feed coleus frequently with a water-soluble fertilizer such as fish emulsion. Follow dilution directions on the bottle. Too much fertilizer will suppress vivid colors so pay attention to how your plants look as you care for them.
Use a free-draining potting or soil mix for containers and plant pots or hanging baskets where coleus will be protected from wind. Coleus branches break easily.
Which brings us back to propagating plants from cuttings. Use a clean knife, pruners or scissors or just break off branches to root for cuttings in clean water or a soilless mixture. If you have a choice, choose cuttings from the top of the plant. Hormonal action is strongest there and your chances of a successful rooting will be increased. When roots have formed, pot up the cuttings and grow indoors or harden to transplant outside.
With coleus, there are just so many choices. Coleus can be upright, trailing or rounded. Leaf texture can be lobed, scalloped, frilled, twisted, elongated or duck footed. With a huge palette of colors from deep burgundy, vivid purple, chocolate brown and neon pink to fluorescent chartreuse, coleus provide you the opportunity to design a bed, pot or garden that ranges from subtle to shocking.
If you decide to try your hand at coleus from seed, you can find Rainbow Floral Strain Mix online at Baker Creek Heirloom Seeds and Swallowtail Garden Seeds.
Workshop: U. C. Master Gardeners of Napa County will hold a workshop on “Toxic and Carnivorous Plants” on Saturday, October 27, from 9:30 a.m. to 11:30 a.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Foxglove. Lily-of-the-valley. Wisteria. These common plants and many others are toxiix. Who knew? Sundew. Venus flytrap. Pitcher plant. Carnivorous, or so we've heard. Join the UC Master Gardeners and explore the fascinating properties that plants have to protect themselves and survive in inhospitable places.Online registration (credit card only);Mail-in/Walk-in registration (check only or drop off cash payment).
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions? Find us on Facebook under UC Master Gardeners of Napa County.