Annuals are indispensable additions to the home landscape because of their colorful flowers and long bloom period. Popular annuals for sunny sites include marigolds, petunias, and geraniums. Impatiens are the perfect choice for locations in partial shade.
Impatiens (Impatiens walleriana) are one of the most popular bedding plants in the United States. They are ideal for containers, hanging baskets, and beds.
Impatiens have glossy, medium-green leaves. Flowers are 1 to 2 inches in diameter, may be single or double, and come in a wide variety of colors. Plants commonly grow 12 to 18 inches tall.
Plants can be purchased at garden centers and greenhouses in spring. Impatiens are also relatively easy to grow from seeds. Home gardeners should sow seeds indoors 8 to 10 weeks before the anticipated outdoor plant date. Older varieties of impatiens such as Accent, Tempo, and Super Elfin series, are occasionally found in garden centers but these varieties are very prone to downy mildew diseases. Newly introduced varieties are resistant to this disease. Recommended downy mildew-resistant cultivars include Beacon™, Bounce™, and Imara® XDR series. Some of these cultivars are crosses between I. walleriana and the downy mildew-resistant New Guinea impatiens. Plants in these series are compact, free flowering, and available in a wide range of colors.
Impatiens perform best in moist, well-drained soils in partial shade. Sites that receive 2 to 4 hours of filtered sun during the day or morning sun and afternoon shade are usually ideal. Impatiens can also be grown in heavy shade. However, plants will be taller and bloom less profusely in heavily shaded locations.
Plant impatiens outdoors after the danger of frost is past. Plants purchased at a greenhouse or started indoors should be "hardened" or acclimated to outdoor conditions for several days prior to planting. Initially place the plants in a shady, protected location and gradually expose them to short periods of sunlight.
Impatiens growing in garden beds usually need to be watered once a week during dry weather. Plants growing in containers or hanging baskets should be checked frequently and watered when the soil surface is dry.
Impatiens require moderate fertilization. Plants in containers should be fertilized approximately every 2 weeks with a water-soluble fertilizer. In flower beds, incorporating a slow-release fertilizer into the soil prior to planting should be adequate.
New Guinea impatiens (Impatiens hawkeri) are native to the island of New Guinea. They were introduced to the United States in 1970. While the initial introductions didn't perform well, plant breeders have introduced many new, improved cultivars over the last 25 years. These newer cultivars have transformed New Guinea impatiens into popular potted and landscape plants.
New Guinea impatiens have green, bronze, or variegated leaves and large, showy flowers. Flowers can be up to 3 inches in diameter. Flower colors vary from white and pale pink to bright pink, red, violet, and orange.
Most New Guinea impatiens are propagated by cuttings. Gardeners can purchase plants at greenhouses and garden centers in spring. A few varieties, such as those in the Java series, can be grown from seeds. New Guinea impatiens seeds should be started indoors 10 to 12 weeks before the anticipated outdoor planting date.
New Guinea impatiens perform best in locations that receive morning sun and afternoon shade. Eastern exposures are often best. Plants that receive too much sun don't bloom well (flowers are smaller and fewer in number) and may have damaged foliage.
New Guinea impatiens require moist, well-drained soils. They do not like wet or dry soils. In wet soils, plants are prone to root rots. Plants wilt badly in dry soils. While wilted plants recover quickly when watered, moisture stress results in the abortion of flower buds and fewer flowers. It may also cause browning of leaf margins and leaf drop.
New Guinea impatiens are not fond of cool night temperatures. It's usually best to plant them outdoors about 2 weeks after the average last spring frost. When planting, set New Guinea impatiens at the same depth they are currently growing.
New Guinea impatiens in containers should be checked frequently. Water plants when the soil surface becomes dry. A deep soaking once a week should be sufficient for plants growing in landscape beds.
New Guinea impatiens require moderate fertilization. Plants growing in pots or other containers should be fertilized approximately every 2 weeks with a water-soluble fertilizer. Incorporation of a slow-release fertilizer into the soil prior to planting should be adequate for plants in landscape beds.
Though popular in years past, rose balsam (Impatiens balsamina) is no longer widely grown in home gardens. It is also known as touch-me-not.
Garden balsam is an erect plant that may grow 1 to 2 1/2 feet tall. Its flowers are double and resemble small camellias or roses. Flower colors include white, cream, pink, rose, purple, red, and bicolors. Though attractive, the flowers are partially hidden by foliage. As a result, rose balsam isn't as showy as other impatiens species. After blooming, plants produce football-shaped pods (fruits). When mature, these pods burst when touched, hence the common name of touch-me-not. Varieties in the Tom Thumb series produce double flowers on 8- to 12-inch-tall plants.
While more difficult to find than other impatiens, garden balsam can be purchased at garden centers. Plants may also be started indoors. Sow seeds indoors 6 to 8 weeks before the anticipated outdoor planting date. Seeds can also be sown directly outdoors after the danger of frost is past.
Garden balsam performs best in partial shade and a moist, well-drained soil. Prior to planting, lightly fertilize the area with a slow-release garden fertilizer. Plants should be watered once a week in dry weather. Garden balsam is most commonly used in beds and borders.
Impatiens are relatively easy to grow from seeds indoors and transplant into the garden after the danger of frost has passed in the spring. Learn more in this article: How to Start Impatiens from Seed
In 2012, impatiens downy mildew appeared on a number of garden impatiens plantings in Iowa. Downy mildew is a serious disease in impatiens caused by the water mold Plasmopara obducens. Symptoms of impatiens downy mildew initially appear as yellowing of infected leaves. The yellow-green foliage may initially be confused with a nutritional deficiency. As the infection progresses, leaves may curl downward and a white, fuzzy growth can be seen on the undersides of the leaves. Severe infections lead to defoliation and blossom drop, leaving bare stems with a few, tiny yellow leaves at the tips of the shoots. Widespread, severe outbreaks of impatiens downy mildew have occurred in recent years.
Susceptible and Resistant Varieties
All varieties of the common garden impatiens (Impatiens walleriana) and interspecific hybrids with an Impatiens walleriana parent (such as Fusion and Butterfly impatiens) are susceptible to Impatiens downy mildew. Garden balsam (Impatiens balsamina) is also considered susceptible to Impatiens downy mildew.
New Guinea impatiens (Impatiens hawkeri) are highly tolerant of this disease. New varieties of impatiens resistant to impatiens downy mildew are being introduced including Beacon™ and Imara® XDR, as well as hybrid cultivars of New Guinea impatiens including, SunPatiens® and Bounce™. No other annuals are infected by this pathogen.
In landscape plantings, control of downy mildew on impatiens with fungicides is not practical. Sanitation is the best management strategy for this disease. Remove and destroy infected plants as soon as they are noticed to reduce the spread to healthy plants and minimize the amount of overwintering inoculum (oospores). Do not place infected plant material in home compost piles. Temperatures in home compost piles often don’t get high enough to kill disease pathogens. Avoid planting susceptible varieties of common garden impatiens in areas that experienced a downy mildew problem the previous year. Plant resistant varieties or shade-tolerant alternatives, such as wax begonias, pansies, lobelia, torenia, caladium, and coleus.
Growing Impatiens (publication)