Horridculture – Mutants

P80704Mutants are the source of many of our favorite cultivars of otherwise simpler specie. Many cultivars of plants with compact, pendulous or fastigiate (strictly vertical) growth, or variegated, bronzed, golden or otherwise abnormally colored foliage, were derived from ‘sports’, which are mutant stems that appear on otherwise normal plants. Thornless blackberries were sports of thorny cultivars. Fruitless mulberry is a sport of white mulberry. There is no shortage of mutants.



By nature, mutants are genetically unstable. A few can easily mutate back to their original and more genetically stable characteristics. Variegated plants are notorious for developing simple green unvariegated foliage. Because it has more chlorophyll, the unvariegated foliage grows faster, and has the potential to eventually overwhelm and replace the variegated foliage. That is why green sports should get pruned out of variegated plants.

‘President Roosevelt’ is the most popular of the few variegated rhododendrons. In nursery production, it gets pruned somewhat regularly to remove green sports. Variegated specimens are rare in landscapes because almost all revert to unvariegated foliage within only a few years.

‘Yellow Wave’ is a cultivar of New Zealand flax with pendulous yellow striped foliage. It can be seen in front of the upright greener foliage in the background. These are not two separate plants stuck together. The more vigorous green foliage is a reverting sport that should have been removed by the ‘gardener’ who is supposed to be ‘maintaining’ this landscape. The green sport is now so developed that it can not be removed without damaging the rest of the ‘Yellow Wave’ growth. It will undoubtedly be left to overwhelm and replace it. Fortunately, the upright green foliage is about as appealing as the ‘Yellow Wave’, so no one will notice the inadequacy of the maintenance. No one ever does.

Mirror Plant

70510As the old fashioned larger mirror plant, Coprosma repens, fell out of favor through the 1990s, several more colorful varieties of a more compact species of mirror plant, Coprosma X kirkii, became popular. (The ‘X’ in the name indicates that it is actually a hybrid of two specie.) Without getting much more than two feet deep, it spreads out laterally like dense evergreen groundcover.

The color is not from bloom, but from the very glossy foliage. It can be variegated with white, gold, red, pink or bronze, or completely brownish bronze. Some varieties stay very shallow. Others can be shorn into low hedges like Japanese boxwood, only shorter. Although mirror plant does not mind partial shade, foliar density and color is best with full sun exposure and occasional watering.

Most modern varieties are known by their cultivar names, without their specie names. For example, Coprosma ‘Tequila Sunrise’ lacks the species name of ‘X kirkii‘. Such omissions might be the result of confusing hybridization with Coprosma repens, for rounder leaves. In other words, some cultivars may be of ‘questionable parentage’. Some are just dwarf cultivars of coprosma repens.

Foliage Shows Its True Colors

70510thumbFlowers were originally colorful only to attract pollinators. Breeding has improved the color and quality of many garden varieties of flowers, to make them more appealing to the people who grow them. Some have been bred so extensively that they are sterile, which defeats the original function of flowers. Now their function is merely to look good in the garden. Improvements are relative.

Foliage is green because it is photosynthetic. Chlorophyll, which is necessary for photosynthesis, happens to be green. Yellow, red, blue, purple, bronze, gray and variegated foliage might not be as efficient at photosynthesis as green foliage, but can be appealing in home gardens. Many plants with colored foliage are inferior to their greener counterparts, but are somehow more popular.

Gray and blue foliage absorbs less sunlight, which can be an advantage in harsh environments. Blue hesper palm and the various blue agaves are from arid deserts. Colorado blue spruce is from high elevations of the Rocky Mountains. Arizona cypress, silver mountain gum, artemesia, lambs’ ears, lavenders, dusty millers and blue junipers all provide distinctively gray or blue foliage.

Golden arborvitaes and junipers can be strikingly gold as new foliage develops in spring, even if the color does not last long. Most plants with gold foliage fade to yellowish green through summer. Golden honeylocusts do not fade as much, so are still mostly yellow by the time they defoliate in winter. Purplish or reddish foliage of purple leaf plum and red Japanese maple holds color better.

Euonymous, English holly, osmanthus, silverberry, hosta and various pittosporums can be variegated with white or yellow. Ivy, and hydrangea can be variegated with white. New Zealand flax and mirror plant can be variegated with gold or bronze, . . . or red or pink. Any unvariegated mutant growth (known as ‘sports’) that appears on variegated plants should be pruned away. Because it has more chlorophyl, it grows more vigorously, so can overwhelm and replace the more desirable variegated foliage.70510thumb+

Algerian Ivy

70329+This is one of those plants that many of us have strong feelings about. Many of us who remember it from when it was more popular in the 1970s might consider Algerian ivy, Hedera canariensis, to be an aggressively invasive weed. Those of us who are less familiar with it might appreciate it as a vigorous and resilient groundcover that gets dense enough to exclude most other weeds.

Without regular pruning for confinement, Algerian ivy grown as groundcover becomes a vine to climb trees, fences, walls and anything else it can get into. As the vines mature and get closer to the top of their support, they develop shrubby adult growth. Algerian ivy can easily ruin the surfaces that it climbs, or overwhelm shrubbery and trees, but might not be so bad on bare concrete walls.

Well contained Algerian ivy might get about two feet deep. The glossy dark green leaves are about six inches wide, with three or five rounded corners. Leaves of vining or adult growth are smaller and more rounded. New plants are very easy to propagate from cuttings or by layering. ‘Ghost ivy’ is delightfully variegated with white, but usually loses variegation as new growth replaces the old.


70215When the weather warms up a bit between frosty weather and winter storms, the rich fragrance of winter blooming daphne, Daphne odora, is at its best. The domed trusses of tiny pale pink flowers are not much wider than a quarter, so are easy to overlook while investigating the source of the fragrance. ‘Aureomarginata’, the standard cultivar, has glossy evergreen leaves with narrow pale yellow margins. Mature plants are only one or two feet high. All parts of the plant are incidentally toxic.

It is no mystery why daphne is rare. It can be rather finicky, and unpredictably so. It purportedly wants rich and slightly acidic soil, in a warm but partially shaded spot; but can be difficult to grow even in ideal conditions. Yet, it is sometimes seen doing well in full sun or in dense soil of questionable quality. To make matters worse, even the healthiest plants live only about five to eight years.