Why Your wallerianas May be Under Threat.
Avid gardeners are growing Impatiens all over the U.S. There are good reasons for this; Busy Lizzys are colorful, easy-to-grow annuals for shade, but a disease now threatens the survival of this old garden favorite. Find out which varieties are vulnerable and which are immune.
|Double Impatiens||I. omeiana|
There are several different types of Impatiens:
- New Guinea Impatiens offer foliage which is sometimes variegated and larger blooms.
- Double Impatiens which feature miniature-rose-like flowers.
- Sun Impatiens which are bred to grow in full sun.
- Yellow Impatiens, a color breakthrough.
- Impatiens balsamina, the old-fashioned garden balsam with tall stems and an upright growth habit.
- Impatiens capensis bears little orange, orchid-like flowers.
- Impatiens omeiana is a unique cold hardy perennial featuring lance-shaped leaves with white veins.
There is truly a Busy Lizzy for every garden.
Native to eastern Africa from Kenya to Mozambique, these tender perennials are usually grown as annuals. Most types are root hardy to roughly 25 degrees F. though, when growing Impatiens in areas colder than zone 10, you should expect the top growth to freeze to the ground.
If you have a special variety or color that you wish to preserve, this can easily be accomplished by taking 5 inch tip cuttings.
Cuttings will root easily and quickly in water or soil and can spend the winter on a windowsill. A kitchen or bathroom window would be ideal as the humidity will be higher.
Planting Impatiens Under Trees
Impatiens and bromeliads thriving at the foot of an oak tree.
Busy Lizzys put on a splendid color show when massed beneath trees.
They enjoy the shade and frost protection the tree gives, but must contend with the much larger and more established tree roots for food and water.
Here’s how you can care for Impatiens when planting them under trees:
- Set each plant into a pocket of soil deep enough for it to establish a healthy root system. Five inches will serve.
- Add a handful of organic compost to the planting hole and mix in a little slow release fertilizer.
- Once all the plants are in place, add a pine straw mulch between them. Pine straw is airy and will not rot the succulent stems of the plants, but it will add organic matter to the soil and keep it cooler and more moist.
- Feed once a month with a bloom booster.
- Lastly, watch your plants. It’s normal for such thin leaved plants to droop in the middle of a summer afternoon. If they are still sagging the next morning, they need more water. If they begin to flower less abundantly, they need an extra feeding.
Diseases Affecting Impatiens
Impatiens Necrotic Spot Virus
These leggy Lizzys need pruning.
Impatiens grow leggy in response to an overabundance of food, water and shade.
Fortunately, this is easy to fix. Just whack them back by half. They will come back bushier and full of buds in a matter of weeks.
If you are growing impatiens that suddenly become stunted, develop brown or yellow circles on the leaves, or black or brown stem discoloration they may be infected with INSV.
This serious disease is spread by western flower thrips. Many other garden plants (more than 300 species) are vulnerable to it. There is no cure and the infection is often fatal. The best way to protect your plant collection is to destroy any plant you believe to be infected.
Downy Mildew and Impatiens
|Impatiens, Tokyo Spring Mix 12 Plants||Impatiens, Candy Box 1 Pkt. (20 seeds)||Impatiens, Vanilla And Berries Mix 1 Pkt. (25 seeds)|
Do not compost infected plants, and be sure to check for signs of infection before propagating plants.
Downy mildew is a fungal disease which is mainly spread by water splashing from leaf to leaf. However, the kind of downy mildew that kills Impatiens is different; it can also be blown around by the wind, and once it gets established in the soil, it can survive there for as long as five years.
It would then infect new Impatiens planted there during this time frame. It would not affect other plants in your garden.
How to Tell if Your Plants are Infected:
A fluffy, white coat will develop on the undersides of the leaves. A few days later, infected plants will wilt, defoliate and collapse.
Can Infected Impatiens be Saved?
This is unlikely. Although most copper fungicides are effective against downy mildew, this effectiveness is not long-lived as the pathogen can rapidly adapt to whatever spray you use.
The best thing to do with suspected carriers is remove them from your garden.
How to Grow Downy-Mildew-Free Impatiens
|Impatiens, (New Guinea) Hot Divine Mix Hybrid, 12 Plants||Impatiens, Fusion Peach Frost, 12 Plants||Balsam, Mix 1 Pkt. (75 seeds)|
Start the plants from seed, or plant resistant varieties. All species are not equally vulnerable. Unfortunately, the most common type (Impatiens walleriana) is highly susceptible. So is I. balsamina.
The good news is that I. hawkeri, the New Guinea Impatiens and SunPatiens tolerate it well and can even be planted where infected I. walleriana plants have recently grown.
If you do grow common garden Impatiens, avoid crowding them. Mildew thrives where air cannot circulate.
Also, water the plants in the morning rather than the evening. This will give water droplets on the foliage time to dry before the temperature drops at night. Cool, damp conditions favor the spread of downy mildew.