Documents: Regional Gardens (Canada) - Prairie:

Painted Nettles- Coleus by Another Name!
by Anne Marie Van Nest
June 16, 2002

Painted nettles or flame nettles are the original names for a group of plants with brilliantly coloured leaves originally grown in Southeast Asia (including Malaysia). These semi-succulent plants have square stems and are now known by the name "coleus". North Americans treat coleus as a moderately fast growing annual that adds consistent colour to the summer garden display. Victorian era gardeners grew coleus as a tender perennial in their glasshouses. This distinction of being a tender perennial sounds like a contradictory label, but it is a plant that lives many years in a frost-free environment.

Coleus were very popular during the Victorian gardening era because they were exotic, bold and initially demanded specialized skills to grow. As time passed, more and more common folks placed coleus in their gardens. Coleus was popular until the late twentieth century (1980's). At that time, only a few new seed varieties had been developed and virtually nobody was growing coleus commercially from cuttings. The plant was most often used for parks bedding or grown in a pot on the windowsill at home. Both scenarios were quite uninspiring. There were few colour choices beyond faded reds and greenish-yellows. The large, plain foliage often was topped with large, unsightly spikes of blue flowers. Interest in coleus waned until recently. 

Why are people once again interested in coleus? Today, a new generation of coleus are making their way to the marketplace. They bear little resemblance to the Victorian coleus. They are available in a rainbow of colours such as pink, green, copper, purple, chartreuse, red, orange, and bronze. Sometimes all of these colours are found in one leaf. Others have colour combinations that include speckling and stripes. These new coleus also may have fringes, lobes, curls, twists, waves, and serrated edges to the leaves. The latest coleus are tougher than ever before. Coleus have been bred to withstand strong sunlight, heat and drought. Coleus heights vary also. Cultivars can now be found that grow from 1 foot (30 cm) to 3 feet (1m). Children and the young-at-heart will appreciate some of the new coleus leaf shapes. Cultivars can be found that are shaped like duck's feet, oak leaves, and paw prints. A tired, boring group of plants now have been given a new life through the dedicated work of plant breeders. These visionary people have given us plenty of eye-candy by changing sizes, shapes, textures and most importantly, the colours of coleus.

Coleus has many benefits in the garden because of its foliage colour. Coleus attract attention the instant they arrive in the garden. Use them in containers, as a massed bedding plant, in hanging baskets, or as a houseplant. Coleus are very versatile. The larger leafed plants should be used as bedding plants while the medium to small-sized foliage plants should be used in baskets or planters. Some coleus can even be trained into a standard form.

Coincidentally, the arrival of a new botanical name was during this new image time. For year's coleus were known botanically as Coleus x hybridus or Coleus blumei. This is no longer true. Taxonomists have changed the name to Solenostemon scutillaroides (so-lee-no-stee'mon skew-tel-ah-ree-oy-dees). This multi-syllable tongue twister does have meaning and was not created to torment "latin-phobia" people. The word Solenostemon is from the Greek word solen, which means tube, and stemon that means stamen. The plant has stamens that are joined at the base of the corolla tube. The second (species) name means resembling Scutellaria, a perennial plant called Skullcap.

Before the coleus explosion, most coleus were grown in locations where they received part shade to full shade. A few rare plants might have tolerated sunnier sites, if they were in northern climates and if they were of a darker foliage colour and were kept well watered. Needless to say, not many grew in the sun. Now with the introduction of sun coleus types, the potential for effective displays is huge. Growing large leafed coleus means that they will wilt in the hot sun. So plant them in a site that is shaded in the afternoon or plant sun coleus in a well-mulched, fertile soil that receives plenty of irrigation. Some cultivars prefer full sun. The more sun they get the better their foliage colours. When buying coleus, try to find a picture to see the true foliage colour. Often coleus do not show their true colours until they are planted outside and start to grow.

Growing coleus is relatively easy. They might require deadheading if the gardener decides that spikes of blue flowers do not combine well with the foliage colour. Flowers left on the plant can also divert nutrients upward instead of to the leaves. Pinch out the centre of the plant before it blooms so that energy is not diverted to flower production and the plant branches out!

Vegetatively propagated coleus from cuttings is a speedy method to obtain new plants. The decision to start coleus from seed versus cuttings must consider several factors. Seed takes about ten weeks before it is ready to be planted outside. Cuttings take a fraction of this time. Coleus will usually root within two weeks and then just grow until they are large enough to contend with the outdoor. Note that coleus grown from cuttings are often reluctant to flower and are easier to maintain as attractive, compact plants which only need a little selective pruning. Pinching can help to maintain foliage colour.

The following are some interesting vegetatively propagated coleus from the Internet and local Niagara nurseries. 'Cranberry Salad' is red on chartreuse with splatters of colour as if a paintball enthusiast has been in the garden. 'Florida Sun Splash' has brightly coloured leaves with a deep burgundy centre accented by a yellowish-green border. The leaves are nicely scalloped at the edges. This coleus is identified as sun tolerant. 'Florida Sun Rose' has rose-pink foliage splashed with burgundy and green. It is also for the sun. 'Solar Storm' has deeply cut leaves that are dark red, green, and mottled with ivory. 'Solar Sunrise' has a different look if it is grown in the sun versus the shade. In the sun it has vivid purples, reds and yellows. In the shade it takes on a more green colour with hints of accent colours. 'Volcano' is a bright red befitting its name.

Anne Marie Van Nest is an Instructor at the Niagara Parks Botanical Gardens & School of Horticulture

The GTI Advisor is produced by the Guelph Turfgrass Institute (http://gti.uoguelph.ca) and is available free on our website or by sending an e-mail to advisor@gti.uoguelph.ca

 

 

 


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