Love impatiens and basil? New downy-mildew resistant varieties out now!

New Impatiens downy mildew resistant, Imara IDX Rose bred by Syngenta.
Photo: Syngenta

Gardeners have struggled with downy mildew on two favorite plants, the shade tolerant and floriferous traditional impatiens and flavorful basil, an easy to grow annual herb. Plant breeders to the rescue! New highly resistant forms of these two favorites will be available in 2019 and 2020.

Downy mildew is a devastating disease that can quickly kill an entire planting of impatiens or basil. This disease spreads easily and quickly, and no sweet basil or traditional impatiens were resistant to it until plant breeders changed that in 2018.

Imara XDR Mix impatiens by Syngenta.
Photo: Syngenta

New downy-mildew resistant impatiens

Traditional impatiens, the go to plant for shady sites, succumbed to a similar but different (from basil) form of downy mildew and many garden centers turned to New Guinea impatiens, a larger plant with darker foliage, and stopped selling the traditional Impatiens walleriana. 

Home gardeners that did find traditional impatiens often planted them to only find in a few weeks, leafless diseased plants that were soon dead from impatiens downy mildew.

Imara XDR  (photo right) is a new, extra disease resistant (XDR) line of Impatiens from Syngenta that will be available this summer. Seven colors and a mixture of this “highly resistant” seed propagated strain will be promoted as “take back the shade” Impatiens.

Beacon impatiens introduced by Pan American.
Photo: Pan American

Also promoted as “highly resistant” to impatiens downy mildew, Beacon is a new line of Impatiens walleriana from Pan American based on Super Elfin impatiens. New ones will have four to six color choices when introduced in 2020.

Introduced to nurseries and retailers at the California Trials this spring of 2019, the series currently offers six core colors and two mixes. A limited supply is available now, with full-scale global availability scheduled for January 2020.

New down mildew-resistant Sweet Basil

Resistant forms of basil first came to commercial growers in 2018, and should be available to home gardeners this summer. Prospera®, a new mildew resistant form of basil from Bar-llan University in Israel, is propagated from seed and is available from Johnny’s Seeds.

Proven Winner's Amazel ™ Basil is downy mildew resistant.
Photo: Proven Winners

You can find other more resistant forms of sweet basil at garden centers and sold under new names such as Amazel™ Basil. This plant comes from Proven Winners and it sets no seed. Grown as plants and sold by Jung Seed, or garden centers that sell Proven Winners plants, Amazel™ Basil is an Italian sweet basil hybrid that produces fewer flowers, but more leaves and shoots. Plants are propagated from cuttings, so only the plants (no seeds) will be available for sale.

Rutgers University plant breeders have also released three downy mildew resistant forms of sweet basil: Rutgers Devotion, Rutgers Obsession, and Rutgers Thunderstruck.

Commercial growers can buy these three new varieties of sweet basil seeds in bulk from VDF Specialty Seeds, which were made available starting in the winter of 2018. Home gardeners will be able to buy seeds once the distribution line is established.  Look for them in 2019!

For more information see
basil:
https://extension.umn.edu/diseases/basil-downy-mildew

impatiens:
https://apps.extension.umn.edu/garden/diagnose/plant/annualperennial/impatiens/plantstunted.html

downy mildew:
https://extension.umn.edu/plant-diseases/leaf-spot-diseases-trees-and-shrubs#downy-mildews-1156512

Author: Mary H. Meyer, Extension Horticulturist