How to Grow Impatiens

Impatiens plants are one of the most popular annual flowers, due to their brightly colored blooms and their ability to grow in shady areas. Although technically tropical perennials, these plants are grown as annuals in all but the warmest regions (zones 10 to 12). The Impatiens genus—one of two genera in the Balsam family of plants—has many dozens of species, two of which are common garden plants. Impatiens flowers take their name from the Latin, impatiens, meaning "impatient." They are so-called because their ripe seed pods will sometimes burst open from even a light touch (as if they were impatient to open).

Two Types of Garden Impatiens

Impatiens walleriana is the common impatiens. The most commonly grown cultivars are short plants, attaining a height of not more than one foot. Some types, such as the 'Super Elfin' series, stay much shorter. Standard impatiens flowers come in a variety of colors, including white, red, pink, violet, coral, purple, and (a relative newcomer) yellow. Common impatiens flowers have much to offer, including shade-tolerance, long-lasting blooms, and brightly colored blossoms that come in a variety of colors. Impatiens flowers have long been one of the dominant bedding plants in North America, especially for shaded areas. They are also used in container gardens, ranging from hanging baskets to window boxes.

However, in 2004, a particular form of downy mildew appeared and quickly decimated breeding stock in commercial nurseries across North America. This disease is caused by a pathogen called Plasmopara obducens, and for more than a decade, it virtually stopped all commercial sale of standard impatiens. Standard impatiens did not begin a comeback until 2019, with the development of a few mildew-resistant hybrids.

The other common form of impatiens is Impatiens hawkeri, which goes by the common name New Guinea impatiens. It is a notably larger plant than standard impatiens and is considered to be showier, especially in terms of its foliage. New Guineas can also take a little more sunshine than can the walleriana species. Many growers prefer the New Guinea type for use in containers. In recent years, perhaps the biggest advantage of the New Guinea type is its resistance to downy mildew.

When impatiens are planted from seeds, it can take several months for them to mature into flowering plants. Thus, they are usually started indoors up to 10 weeks before the last expected frost date. More often, impatiens are planted from nursery seedlings that are already near flowering maturity.

Impatiens Care

Impatiens are easy to grow in any moist, well-drained soil in a shady or semi-shady location. New Guinea impatiens will tolerate more sun than do standard impatiens. In northern United States and areas with similarly cold winters, the traditional time for planting impatiens is Memorial Day, when the danger of frost has passed. If planted in soil that is too cold, these plants will languish for the entire growing season. After planting, pinching back the stems will encourage bushier growth.

While the plant is quite popular, don't let the claim that this plant is "overused" hold too much sway over your buying decisions. If a particular color of impatiens helps fill a need in a flower border or anywhere else, especially in shaded areas, you are well-advised to use it.

Light

With sufficient water impatiens can be grown in a part sun location in northerly regions, their great virtue is that they thrive in the shade. In fact, they're among the relatively few readily available, inexpensive flowering plants that will put on a great floral display even when grown in full shade. The New Guinea forms are much more tolerant of sun and can even thrive in full sun if watered frequently.

Soil

Grow impatiens flowers in well-drained soil enriched with organic material. The soil must drain well to avoid becoming boggy from the frequent watering that impatiens require.

Water

Once in the ground, the impatiens will need at least two inches of water a week. When temperatures average consistently above 80 degrees, water at least four inches weekly. In window boxes and hanging pots, impatiens may need watering daily.

Temperature and Humidity

Impatiens are quite sensitive to heat. If your temperatures rise above 85 degrees Fahrenheit, they will require at least four inches of water per week. Container impatiens will need daily watering—or twice daily if temperatures are above 85 degrees. If there has been a long, dry spell, your plants will likely look wilted. Thankfully, they bounce back quickly. Give them some water and they will perk back up.

Impatiens are tropical plants that will turn to mush at the first light frost. Bring them indoors if you plan to keep them over the colder months. They are fine in humid weather.

Fertilizer

Impatiens will flower best if regularly fertilized. A water-soluble fertilizer can be used every two weeks throughout the spring and summer. Another option is a slow-release fertilizer used at the beginning of the spring and again halfway through the summer. If your impatiens plants start looking leggy late in the summer, use scissors to trim off the top one-third of their vegetation. This will promote the emergence of new blooms and improve the overall appearance of the plants. One possible cause of legginess is over-fertilization.

Impatiens Varieties

There are more than a thousand varieties of impatiens. Standard impatiens may still be hard to find, since mildew-resistant varieties are still being developed and introduced. Your best selection may come with New Guinea impatiens. Some recommended varieties of standard and New Guinea impatiens include:

• Impatiens walleriana 'Imara XDR': This line is a new disease-resistant line of standard impatiens from the Syngenta company, which became available in 2019. There are seven colors as well as color mixes in this series, which promises to restore standard impatiens to their former popularity.
• Impatiens walleriana 'Beacon': This is another series of standard impatiens that is "highly resistant" to mildew, introduced in 2020. Beacon is derived from the Super Elfin line, with many colors available.
• Impatiens hawkeri 'Celebration' series: This is one of the best of the New Guinea impatiens. Available in a wide range of vibrant colors, these plants grow to 16 inches tall. These plants were likely hybridized with other species of impatiens.
• Impatiens x 'Bounce' series: Developed by Ball Horticultural Company, this hybrid series of impatiens is a cross between New Guinea and standard impatiens. According to the company, they are resistant to downy mildew and thrive in sun and shade. It "bounces back" nicely after wilting in hot weather.
• Impatiens x 'SunPatiens' series: This variety of New Guinea impatiens has unusually large flowers (up to 3 inches across) in a unique shade of salmon pink. At up to 3 feet tall, the Sunpatiens line is across between New Guinea impatiens and standard impatiens species.

Propagating Impatiens

Impatiens will readily self-seed themselves, even in colder climates, though it may take most of the following year's growing season before the seeds produce flowering plants. Some gardeners also collect seeds from the "exploding" pods that the plants produce in late summer and fall, then start them indoors in a seed-starting mix in later winter, six to 10 weeks before the last frost.

It is easier to propagate impatiens from cuttings taken in the fall:

1. Clip a plant shoot 4 to 6 inches long, with ample leaves. Pinch off the bottom sets of leaves, as well as any flowers or seed pods.
2. Suspend the cutting in water and place it in a bright area but out of direct sunlight. Replace the water frequently (every few days) as it becomes cloudy.
3. When a good network of roots has developed, plant the cutting in potting soil or a mixture of soil and vermiculite or perlite. Continue to grow in a bright area out of direct sunlight. Keep the potting soil consistently moist.
4. Plant in the garden after the last frost has passed in the spring.

Common Pests/ Diseases

Aside from the downy mildew that devastated the standard impatiens, these plants can be affected by viruses, fungal blights, and rots. These problems are more likely in humid, wet conditions or where plants are crowded together too closely.

Insect problems include aphids, mealybugs, thrips, whitefly, slugs, snails, and spider mites. Severely affected plants can be removed; minor infestations can be treated with horticultural oils or pesticides.

Too much sun may scorch the leaves on most varieties of impatiens, though the New Guinea varieties can usually tolerate full sun if given extra moisture.