Protecting Hollyhocks From Rust
Thursday, October 23, 2008
Q In late summer last year, I grew hollyhocks from seed. They grew well, and in the spring they started to produce flower buds. They became covered, though, in a rust-like fungus. I tried to treat the leaves with a fungicide, to no avail. Will they come back next year, and how will I fight the disease then?
Rust was worse than normal on many plants this spring, including hollyhocks. This was due to wet weather as the spores were released.
Good sanitation this fall is important. Remove all leaves and stems after the first hard frost, cutting the plants back to the soil surface. And keep your garden free of weeds over the winter and early spring, because hollyhock rust also thrives on cheeseweed, a common weed that, like the hollyhock, is a member of the mallow family.
In the spring, begin to treat your hollyhocks with a fungicide as soon as new leaves begin to grow. Many fungicides are labeled for rust diseases but will need to be applied several times. You can discontinue the fungicide when hot weather arrives, usually by June.
One hollyhock species, Alcea rugosa, has a good degree of resistance to rust. Its flowers are a bright shade of pastel yellow, and its deep-green, rough leaves provide interest when the plant is out of bloom.
We received as a gift a jasmine plant with white blossoms. How do we get this to rebloom? Can it be safely planted outdoors, or should it be kept as an indoor plant?
Although it may survive in a sheltered location, it is likely to die back to the ground in the winter. It naturally blooms in response to short days, so if you want to enjoy the flowers again, you will have to grow it indoors during the colder months.
You can keep the plant outdoors in the summer, either in a container with a trellis or in a hanging basket. Water daily if rain doesn't do the job, and fertilize the plant with liquid plant food according to label directions every month. Bring it indoors at this time of year, before a hard frost.
Once indoors, discontinue the monthly fertilization and cut back on watering. Put it in a sunny window in a room that is kept as cool as possible. By keeping it below 65 degrees, it will bloom again in spring.
Scott Aker is a horticulturist at the U.S. National Arboretum.