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by Leonard Perry
by Leonard Perry


In extension I serve as an advisor and consultant to the greenhouse and nursery industry, primarily in Vermont but throughout the region and beyond as well.

I give presentations on my research to the industry, and to home groups. In Research, my focus is "herbaceous perennial production systems".

His website is at  Leonards zone of gardening: home with my trials, generally USDA 4a. Campus in Burlington is 5.

April 14, 2013

Impatiens, busy lizzy, or touch-me-not are all names you may see for this common and popular annual flower. It comes in many flower colors, with selections for either sun or shade. A new disease, however, is limiting the use and sale of the shade impatiens so you may need to seek alternative flowers if your garden gets little sun.

The shade impatiens (Impatiens walleriana) is just one of 500 species in the Balsam family or Balsaminaceae, which includes the old-fashioned garden balsam (I. balsamina) and the newer hybrid New Guinea impatiens (I. hawkeri). The latter was introduced from a plant exploration on this South Pacific island in 1970. There are several other impatiens you may see, such as the 3 to 4-foot tall jewelweed (I. capensis), whose orange flowers the hummingbirds love but gardeners may hate as it self-sows readily.

The name comes from the fact they are “impatient” to eject their seeds, as the slightest touch will cause ripe seedpods to open and scatter seeds to the wind. Originally thought to be indigenous to Zanzibar (an African island now part of Tanzania), the shade impatiens also was found to grow in the eastern regions of equatorial Africa. It was introduced to the western world in 1896 by Dr. John Kirk, a renowned British physician and naturalist who accompanied Dr. Livingstone on many of his African expeditions.

As might be assumed, the shade impatiens should receive part shade (less than 6 hours direct sun per day), and will tolerate filtered sun to full shade. Although today's impatiens varieties are more sun-tolerant than older varieties, too much sun will cause impatiens to have small leaves, few blooms, and little height. You may see these called “bedding” impatiens as they are commonly massed in garden beds.

Shade impatiens can be planted under trees although special care is needed, as the tree roots will compete with the flowers for space, water, and nutrients. Impatiens planted here will require frequent watering and additional fertilizer, as will mature plants in containers. One easy solution under trees is to construct a slightly raised garden six to eight feet from the tree. Or you can dig out roots, if they are some distance from the tree, and fill the holes with a soil mix for planting.

Other impatiens, such as the popular New Guinea cultivars (cultivated varieties), grow in full sun in the north, but tolerate part shade and in the south need part shade. Make sure they are kept well-watered if in sun, but are in well-drained soil as all impatiens like. If they do wilt, unless severely, they should revive soon with watering.

Plants of shade impatiens generally grow from six to eighteen inches tall, depending on series, and one to two feet wide. Size will vary, depending on the spacing, moisture, available nutrients, and amount of sunlight. Flower form can be single, semidouble, or fully double blooms.

New Guinea impatiens are generally upright with less spread. Flowers are single but up to two times larger than those of shade impatiens, and often in more brilliant and bright colors. Their foliage is much larger, stiffer, elliptical, and often in dark green to purplish colors. They are generally propagated by cuttings, while shade impatiens are generally from seeds. New Guinea impatiens, too, can be massed in beds but also are effective in fronts of beds, along walks, and in containers.’

Impatiens are often found in a named “series”, having up to two dozen or more flower color choices in each. Examples of shorter series of the shade impatiens with single flowers include Accent, Carnival, Dazzler, Infinity, Super Elfin, and Swirl. Series on the taller side with single flowers include Blitz, Shady Lady, and Tempo. Taller series with double flowers include Cameo, Carousel, Confection, and Fiesta.

Some popular series of New Guinea impatiens, again in many colors but not so many choices as with shade impatiens, include Celebrate, Gem, Harmony, Java, Lasting Impressions, Ovation, Paradise, Petticoat, Pizzazz, Pretty Girl, Pure Beauty, and Riviera. There are several named cultivars not in series, such as the orange-flowered Tango—an All-America Selections winner in 1989, and one of the first to be grown from seeds.

If starting impatiens from seed, sow indoors 8 to 10 weeks prior to planting outdoors after the last frost. “Harden off” seedlings before transplanting outdoors, putting them out in part shade and bringing them in on frosty nights. If buying plants in spring, choose ones that aren’t wilted or showing signs of stress, with good leaf color, and well-branched.

When planting, remember that the more tightly they are spaced, the taller they will grow. They’ll fill in sooner if closely spaced, but you’ll need more plants. For example, if plants are used for a border, space them eight to 12 inches apart so they will spread but remain low growing. Mix in compost before transplanting, especially if a sandy or clay soil.

If you want to grow impatiens in window boxes or other containers, use a sterile or soil-less growing mixture rather than garden soil to allow for better drainage. Space according to the height you wish the plants to attain. Remember, container plants will need more frequent watering than plants grown in gardens.

Water thoroughly after planting, and continue to water throughout the growing season if it doesn’t rain. Keep soil moist, but avoid overwatering as this could encourage fungal diseases. Avoid overhead watering late in the day as the foliage will not have sufficient time to dry before nightfall and will be more prone to disease. Fertilize impatiens frequently, according to label directions on your product of choice.

A couple of less serious impatiens problems for most include a virus and a fungus. Impatiens necrotic spot virus is carried between plants by the tiny thrips insect, and may cause stunting, ringspots on leaves, or brown to purple spots on leaves and stems. Unless severe, plants usually live. If plants are too wet or with insufficient space and air movement, they may get rhizoctonia crown rot. This fungus may cause yellowing, wilting, and plant collapse. Prevent it with proper culture, and neem oil sprays if the disease is suspected.

The worst disease and a new one, with no good controls nor fungicides for home gardeners, is fortunately a problem just on the shade impatiens. Impatiens downy mildew has spread widely in the plant industry, and is the reason many growers have stopped selling these impatiens. Unique to this plant species, it is different from downy mildews of other plants. Symptoms begin with leaves slightly curling downward, yellowing, then growth becoming stunted. A white downy coating can be seen on undersides of leaves. Plants can soon drop all leaves and flowers and collapse.

To avoid impatiens downy mildew, inspect plants before purchase. Don’t plant where you had impatiens die from this previously. Use good culture and plant spacing. If impatiens are infected, remove plants as the disease can live on the dead debris. Throw infected plants in the trash, not the compost. You can start plants from seeds, as these don’t carry the disease. The SunPatiens brand has shown high resistance to this disease. Or, alternative plants you may consider are caladium, coleus, begonias (there is a huge range of these to choose from), browallia, torenia, polka-dot plant, and New Guinea impatiens.

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