Impatiens are some of the most popular annual flowers for shady beds and borders. Their colorful blooms provide a burst of color in otherwise darker parts of the garden. However, in recent years, downy mildew has devastated impatiens plants across North America. This fungal disease results in yellowing leaves, stunted growth, and eventual plant death.
Fortunately, plant breeders have been hard at work developing new downy mildew-resistant impatiens varieties. If you love growing impatiens but have had issues with downy mildew, consider switching to one of these resistant hybrids or species.
What is Downy Mildew?
Before discussing resistant varieties, let’s take a moment to better understand this impatiens disease.
Downy mildew is caused by the fungal-like organism Plasmopara obducens. Spores spread through water splash from rain and overhead irrigation. When conditions are cool and humid, downy mildew thrives.
Initial symptoms include yellowing between leaf veins and on leaf undersides. A downy gray fungal growth may be visible on the undersides of leaves. As the disease progresses, plants are stunted and flowers drop. Eventually the impatiens will collapse and die.
Downy mildew spreads rapidly through impatiens beds. And once plants are infected, there is no cure. Prevention with resistant varieties is key.
Hybrid Impatiens Varieties with Resistance
Through selective breeding, horticulturalists have developed hybrid impatiens with strong downy mildew resistance. These varieties exhibit excellent tolerance when exposed to the disease. Here are some top options:
1. Beacon Impatiens
Beacon impatiens (Impatiens walleriana) were specifically developed to be resistant to downy mildew while still providing the lush foliage and flowers impatiens are known for.
These hybrids come in a range of bright colors including red, coral, orange, pink, white, lavender, and mix. They grow 12-20 inches tall with a mounded habit. Flowers are 2-3 inches across.
With their vibrant blooms and disease resistance, Beacon impatiens are excellent for mass plantings in landscape beds. They also work nicely in containers on shady patios.
2. Imara XDR Impatiens
Bred by Syngenta, Imara XDR impatiens showcase strong tolerance to downy mildew while displaying excellent garden performance. They are vigorous, blooming freely all season with bright flowers.
Imara impatiens come in a wide color range including red, pink, violet, orange, white, and mix. Plants grow 14-16 inches tall and wide. The flowers measure 2-3 inches in diameter.
These impatiens do well in partial shade beds and combine nicely with other shade annuals. Their uniform habit also makes them a great option for potted plantings.
3. Big Bounce Impatiens
Developed by Ball Horticultural, Big Bounce impatiens live up to their name, producing big, bold flowers and strong, vigorous growth. These hybrids show a high degree of downy mildew tolerance.
Big Bounce impatiens produce extra-large blooms up to 3 inches across. Colors include bright red, pink, violet, white, and mix. Plants grow 20-24 inches tall with a mounded form.
Plant Big Bounce impatiens in garden beds and borders, under trees, or in containers. Give them partial sun to partial shade. Deadheading encourages continuous flowering.
4. Sweet SunPatiens Impatiens
If you’re looking for impatiens that can handle more sun along with downy mildew resistance, check out Sweet SunPatiens. Developed by Sakata Seed, these vigorous hybrids tolerate full sun better than standard impatiens.
Sweet SunPatiens produce abundant blooms in shades of red, coral, pink, rose, white, and mix. Plants grow 16-30 inches tall depending on variety. Spread is 14-24 inches.
Use these impatiens in sunny to partly shady beds and borders. Their vigor also makes them great for pots and window boxes in sunnier spots.
Downy Mildew Resistant Species
In addition to new hybrids, several impatiens species naturally exhibit strong downy mildew resistance. Check out these species if you want tried-and-true mildew tolerance.
5. Busy Lizzie (Impatiens walleriana)
Busy Lizzie is the impatiens species from which most modern garden impatiens are derived. As a species, Busy Lizzies show better downy mildew resistance than many hybrids. They are smaller and less floriferous but make up for it with their carefree growth.
Busy Lizzies grow 8-12 inches tall as mounded subshrubs. Flowers come in shades of red, pink, white, purple, and orange. Give these impatiens partial shade and evenly moist soil. Use them in informal cottage gardens or containers.
6. New Guinea Impatiens (Impatiens hawkeri)
Originally from New Guinea, these tropical-looking impatiens feature colorful foliage and exotic blooms. New Guinea impatiens are not closely related to standard impatiens, and they exhibit excellent resistance to downy mildew.
In New Guinea impatiens, the leaves are just as showy as the flowers. Foliage comes in shades of green, bronze, variegated, and more. Flowers stand above the leaves on short stems and come in bright shades of red, orange, pink, white, purple, and mix. Plants grow 1-2 feet tall and wide.
New Guinea impatiens thrive in humid, partially shady tropical conditions. Use them in beds and borders or shade containers. Regular deadheading encourages more blooms.
7. SunPatiens Impatiens (Impatiens hawkeri)
If you like the look of New Guinea impatiens but need varieties for sunnier spots, SunPatiens are the solution. As the name suggests, these impatiens handle full sun better than standard varieties. And they exhibit excellent resistance to downy mildew.
In addition to their sun tolerance, SunPatiens produce massive flowers up to 2.5 inches across. Flower colors include bright shades of red, orange, pink, violet, and white. Plants grow 16-36 inches tall depending on variety.
Use vigorous SunPatiens in landscape plantings, hanging baskets, window boxes, and containers placed in full sun to partial shade.
8. Balsam (Impatiens balsamina)
An old-fashioned annual, balsam impatiens are prized for their abundant flowers and disease resistance. Native to tropical Asia and Africa, balsams thrive in hot, humid climates.
Balsams produce dense flowers along the stems, giving them a different look than standard impatiens. Blooms come in shades of pink, red, white, lavender, and mix. Plants grow 1-2 feet tall.
Grow balsam impatiens from seed started indoors. Move them outside after frost danger has passed. Give these heat-loving annuals full sun to thrive. Use them in cottage gardens, pots, and hanging baskets.
9. Touch-Me-Not (Impatiens capensis)
Also called jewelweed, touch-me-not is a wild impatiens species native to damp woodlands. Hummingbirds love their showy flowers. And touch-me-nots exhibit excellent resistance to downy mildew and other diseases.
Touch-me-not grows 2-4 feet tall on juicy translucent stems. The bisexual flowers are orange with reddish brown spots. When mature, the seed pods burst open when touched, giving this plant its common name.
While touch-me-not can be planted in gardens, it often seeds itself prolifically and spreads rapidly. Site it carefully or grow it in containers. Provide rich, moist soil and partial shade.
Growing Tips for Downy Mildew Resistant Impatiens
Here are some key tips to get the most out of your downy mildew resistant impatiens:
- Give impatiens rich, humus-rich, well-draining soil. Amend with compost or peat moss if needed.
- Site impatiens in areas with partial shade to full shade. Most tolerate only minimal sun exposure, especially in hot climates.
- Space plants 10-14 inches apart to allow for growth and airflow. Crowding increases humidity and disease risk.
- Water impatiens regularly to keep the soil evenly moist. Allow the soil to dry slightly between waterings.
- Apply a layer of mulch around plants to retain soil moisture and suppress weeds.
- Deadhead spent blooms to encourage continuous flowering through the season.
- Watch for other pests like aphids, spider mites, and thrips. Control with horticultural oils or insecticidal soaps.
- In fall, pull up and discard impatiens plants to prevent overwintering of downy mildew.
Transform Your Shady Gardens with Downy Mildew Resistant Impatiens
If downy mildew has you wary of growing impatiens, it’s time to give resistant varieties a try in your garden. With their lush foliage and bountiful blooms in vivid colors, these newer impatiens selections bring life back to shaded beds, borders, and containers.
By choosing resistant hybrids and species, you can again enjoy vibrant impatiens without the headaches of this persistent disease. Just provide the right growing conditions, and your impatiens will thrive and bloom non-stop once more.