My impatiens look thin and leafless like what you described as downy mildew. Am I doomed? Can I ever plant impatiens again? - J.D. -
If it is downy mildew, we would not plan on planting impatiens again.
If we haven't had it in a garden yet we will consider using impatiens. Any year we plant them may be the last, but we'd do it if we haven't seen it in a particular place and can afford the chance that it may show up at any time, cutting the season short by killing the plants. That one last season with this incredible plant may be worth it.
Do be sure it is downy mildew. Very often, end of summer impatiens look stretched, partially defoliated and shy on bloom yet they are disease-free. What they are, is starved!
Left, and below: Look at leaves from the plants
pictured at the top of this page. They do not have
any downy white on their undersides, and when held
up to the light we do not see any early signs of
... signs such as discolored spots developing within the leaf.
It's not reasonable to expect great growth if you put one or several of these mighty growers into a pot or tube of soilless potting soil and never fertilize them. This year, even if you fertilized regularly you might now see some starvation in container plants. That's because we had to water so much more to fend off the drought and heat. All that water kept leaching away what little nutrients the pot may have held.
Right: Notice that the lowest leaves are turning yellow
and dropping off but the newest foliage at the top of
each branch is a healthy green. That's the plant's own
doing. It's scavenging nitrogen from older leaves and incorporating it into the newer foliage that is getting
more light and can do more with it.
Soilless mix is the way to go for drainage, but you must then be faithful with fertilizer since the mix itself is nutrient-poor. It is a help to mix slow release fertilizer into the soilless mix at the beginning of the year but water soluble supplements every week or two are better for these heavy feeders. Use a blue-powder fertilizer at half strength every two weeks, and dilute it a bit more to add it every week in an exceptionally hot, dry year.
Click for the full story on impatiens downy mildew.