October 2002

Lamium ‘Orchid Frost’ Spotted Deed Nettle By Paul Pilon

Versatile perennials, lamiums can be utilized in a number of commercial and garden situations. They look great in containers, alone or mixed with other plants in patio pots, window boxes or hanging baskets. In the landscape, they work well as a groundcover in mass plantings or to add foliage color and texture to mixed annual or perennial beds.

Lamium ‘Orchid Frost’ is a mat-forming perennial groundcover that offers many improvements over other cultivars of this species. Orchid Frost is a cultivar of Lamium maculatum, which belongs to the mint family. Unlike most varieties of lamiums, Orchid Frost holds up remarkably well during the summer months, without foliage scorching or being overcome with leaf spots. It bears bright, orchid-pink flowers during both the spring and the fall over its variegated silver foliage.

Orchid Frost thrives in full sun or partial shade and grows rapidly, spreading 12-16 inches wide, while maintaining a height of 4-6 inches. Like most dead nettles, Orchid Frost is evergreen in southern climates or regions, because of the mild winters. Hardy in Zones 4-8, Orchid Frost was selected by American plantsman Mike Bovio of Michigan and has been brought to the marketplace by PlantHaven Inc., Santa Barbara, Calif.

Propagation

Most lamiums are propagated by vegetative cuttings, as is Orchid Frost. However, this cultivar is patented, and a license is required for commercial propagation. As a result, most finish growers buy-in rooted liners. Plugs acquired from propagators range in size from a 128 cell to a 3-inch liner.

As a general background, propagators typically root a finished cutting in four weeks. Soil temperature is maintained between 70-75º F by providing bottom heat, which enhances root development. To accelerate rooting and improve uniformity, the base of each cutting is dipped in a 1,500 ppm IBA rooting hormone prior to planting.

Production

Orchid Frost performs best when grown in a moist, well-drained medium with a slightly acidic pH of 5.5-6.3. It is a light to moderate feeder and prefers either a constant liquid fertilization program, feeding at rates of 50-100 ppm nitrate, or a controlled-release fertilizer at a rate equivalent to 1 to 1 1/2 pounds of nitrogen per yard of growing medium. Lamiums prefer to be kept moist, but not consistently wet. Plants grown under drier conditions may struggle but will persist.

For plant establishment, it is recommended to maintain average temperatures of at least 65º F. Once lamiums are established, you can grow them with 55-70º F day temperatures and night temperatures of 55-60º F. At these temperatures, a quart-sized pot can be finished from a 128-size plug in 4-6 weeks. Plants grown at warmer temperatures with low light levels will often become straggly, with reduced quality characteristics. Á

Even though plants can tolerate being produced under shady conditions, it is best to produce Orchid Frost under high light levels with a minimum of 5,000-6,000 foot-candles. Please note that many lamium cultivars do not perform as well at these light levels, often getting scorched leaves as a result.

Pinching is not necessary with Orchid Frost, as plants branch freely. They may be trimmed to shape growth or cut back if desired. Many growers trim or mow the foliage back in the summer, after flowering is finished, to rejuvenate plant growth and to help keep the foliage free of leaf spots.

Orchid Frost can be produced at high plant densities. However, the highest-quality plant is produced with at least a minimum of spacing, i.e. a 1-quart grown at 5-inch centers or a 1-gallon grown at 10-inch centers.

For spring shipping of lamium Orchid Frost in bloom, I would typically suggest planting two 128-cell plugs into a 1-gallon container in late summer. This allows plants to become established and to fill out the pot prior to winter.

Over-wintering of lamiums is a rather simple procedure. If necessary, trim the plants back to 2-3 inches above the top of the container, and group them together inside a coldframe or greenhouse structure in late fall. A coldframe covered with a single layer of white plastic will provide adequate protection during the winter months. During this season, if there are periods where temperatures remain above freezing, open the coldframe doors or provide ventilation during the day to keep the temperatures inside as cool as possible. Once more spring-like conditions are present and Orchid Frost is actively growing, space out the containers. Keep the coldframe doors open any time outdoor temperatures are above 40º F. Every spring and every location is different, but in our Zone (Zone 5) it is not uncommon to have flowering plants ready for shipping by mid-April when the above guidelines are followed.

Chemical Needs

When produced under high-light intensities and adequate spacing, height control is seldom an issue. If controlling plant height is necessary, depending on your geographic location, apply Sumagic at 5-10 ppm, Bonzi at 30-60 ppm or Cycocel at 1,000-1,500 ppm. If growth regulators are necessary, Orchid Frost will usually require 2-3 applications at 7-day intervals to provide adequate height control. Begin the chemical growth regulator applications as the plant canopy encloses.

The occurrence of insects is not uncommon, but rarely is it problematic. Whiteflies are the most troublesome insect pests of lamiums, but occasional outbreaks of aphids, slugs and snails may occur. When Orchid Frost is grown at high plant densities, I usually apply a preventative drench application of Marathon 60WP to ensure the absence of aphids and whiteflies for the duration of the production cycle.

There are potentially more disease problems than insect pests. Common diseases of lamiums include purplish fungal leaf spots, downy mildew, Botrytis and crown rots. In most cases, the foliar diseases can be prevented or reduced by providing adequate spacing and good air circulation at all times, maintaining a relative humidity below 70 percent and, if necessary, using a preventative fungicide spray program (especially for downy mildew). Excessive irrigation, poorly drained growing medium and excessive periods of heavy rainfall could lead to crown or stem rots and ultimately, plant loss.

Lamium Orchid Frost is widely available as a plug or finished container from many reputable companies across the country. Orchid Frost has also been selected and is being promoted by the Paul Ecke Ranch under The Flower Fields brand of perennials.