Disease in Impatiens and Replacement Plantings

Impatiens Downy Mildew

Landscapers and gardeners in Maryland, Northern Virginia, and Washington D.C. are facing a new challenge this year. There has been an outbreak of an aggressive fungal disease that, at least for the short term, has virtually eliminated the planting of the extremely popular and useful shade-tolerant annual impatiens. The disease is called impatiens downy mildew. It manifests itself with reduced vigor, pale foliage, and inconspicuous mottling. As the disease progresses landscapes face stunted plant growth, wilting, and soon, extreme leaf drop. While it is technically possible to treat planting beds with fungicides and reduce the risk of the disease, treatment is not really practical in most settings, as impatiens downy mildew is so wide spread.

As a landscape design company in Montgomery County, Maryland, landscape maintenance is an important service to many of our best clients and enables us to continue to be involved in the evolution of their gardens. We have traditionally used impatiens to bring color and life into the shadier parts of a property. We have also planted them in a more “gardenesque” manner where they weave in and out of foliage perennials and shrubs throughout the garden to highlight other plantings and provide a subtle sense of rhythm.

Production of these wonderful flowers in their myriad of colors has almost ceased for the time being, forcing us to be creative in finding substitutions.

Replacements for Impatiens

Shade Annuals

There are some obvious and very good replacement shade annuals, chief among them the Begonias, Coleus, Caladiums, and Torenia. While none of these flowers have quite the color intensity and density of the impatiens, they each have their own appeal and potential.

• Dragon Wing Begonias. We especially love these begonias for their stature and lush green waxy leaves.
• Coleus. Coleus can bring a wide range of bright colors into the shade garden. We focus particularly on the Wizard series, which are shade tolerant, rather than the wonderful “Sun Coleus” that we use extensively in sunnier areas.
• Cladiums. Caladiums are similar to Coleus in that they are foliage plants with large and very colorful leaves. With their coarse texture, caladiums add an exotic, almost tropical tone to the garden. This can be great for landscapes with a modern aesthetic that we often design in urban parts of Washington, like Logan Circle, Dupont , Adams Morgan, and the U Street corridor. Caladium can also be very compelling and evocative in landscape designs that have a gracious Southern atmosphere, a style that many of our clients strive for in areas of Northern Virginia, like Alexandria, Arlington, and Fairfax.
• Wax Begonias and Torenia. For a finer texture and more subtle approach, our landscape design team will consider the old fashioned Wax Begonias and the lesser known Torenia. This shade annual is exciting since it can bring tones of blue and purple into the landscape. We especially love the upright “Clown” series, but the cascading “Moon” varieties are also quite useful.

Substituting Impatiens in Sunnier Outdoor Spaces

Another approach we take is to locate the seasonal colors in slightly brighter areas. For sunnier outdoor spaces we consider the following plants:

• New Guinea Impatiens. These plants are highly resistant to impatiens downy mildew, and some have color ranges similar to traditional impatiens.
• Vinca rosea. We also like Vinca rosea as a “workhorse” annual.
• Nicotiana. The flowering ornamental tobacco Nicotiana can add great height, texture, form, and a more esoteric note. We would consider these plants for a client who is more of a gardener and willing to do some dead heading.
• “Sun Loving” plants. On a limited scale, our landscape designers will consider pushing the envelope and introducing annuals that are traditionally thought of as sun loving. Possibilities include Geraniums, Lobelia, Ipomoea (Potato Vine), Petunias, and Salvia.

Shade Loving Perennials

We also add shade loving perennials as a substitute for impatiens in low maintenance and sustainable gardens.

Good candidates include the following:

• Plants with colored foliage. Examples include Hostas, Heucheras and Ajuga, as well as the new varieties of variegated Brunnera (Perennial Forget-Me-Not), and Hakonechloa (Japanese River Grass).
• Flowers. We look to Hellebores, Astilbe, and the perennial Geranium.

Landscape & Plantings at Botanical Decorators

We are looking at impatiens downy mildew as a challenge and an opportunity to stretch and grow. For now, we are bidding a reluctant farewell to the indispensable color of impatiens. It seems likely that it will be years before horticulturists develop a new variety that is disease resistant. In the meantime, we are experimenting with a wide variety of wonderful alternative plantings.

If you are interested in incorporating a garden into your landscape design, check out some of our recent landscape and planting projects throughout Maryland, Virginia, and Washington, DC.