Hi again
This Spring, I planted numerous cimicifuga ramosa along with ostrich ferns on the south side of my house. This is a part shade /sun area on my land, which gets around 4 hours of sun every day.
The cimicifuga ramosa were expected to grow up to 5-6 feet tall. Strangely and even if they are barely feet apart on the same strip of land and have been watered the same way, some cimicifuga ramosa have grown as expected whereas others have barely grown at all this Summer although nothing suggests that they are diseased or dying.
What could I do now, this coming Fall and next Spring to address the growth issue of the cimicifuga ramosa?
Thanks again for your time and expertise.
Interestingly, the taller plant in your picture is the unusual one, not the shorter ones. This plant, also called Actea racemosa, Black Snakeroot, Black Cohosh or Bugbane, is notoriously slow to establish, taking several years to reach maturity, so I would expect them to be small at this point.
Although one of the plants has grown surprisingly quickly, I am concerned that the bed is not ideal for their future success. In the wild, they grow in moist, rich, humus soil in a woodland setting, in shady or semi-shady conditions. They do tolerate poor drainage, and enjoy damp, acid, soil. As described in our Gardening Guide to Hardy Ferns, Ostrich ferns also enjoy moist humus-rich soil in shade, although they will tolerate sun if in a moist, cool location.
A south-facing bed close to the foundation and in front of a light-coloured wall would not be the best location for either plant.
- There is probably a “rain shadow” there, i.e. the roof eaves prevent rain from falling directly on the bed.
- The concrete in the foundation leaches lime, adding a basic element to the soil, exactly the opposite of acid.
- In the photo, the bed doesn’t appear very shaded at all. I suspect the bed is getting 4 to 6 hours of morning sun and may be exposed to the noon-hour sun.
- The bed is probably very hot, even if partially shaded, due to light reflected from the wall.
- Finally, it is hard to tell from the photo, but the bed appears to be too small for so many plants. Each Cimicifuga racemosa can reach 60-90 cm (2-3 feet) in spread, as do the Ostrich ferns.
All that being said, although they also don’t like to be transplanted, if these were mine, I would relocate the plants to a more suitable location either this fall or in the spring.
You can learn more about growing these Cimicifuga racemosa in these publications from Cornell and the University of Saskatchewan.
You will find this plant in our Gardening Guide for Perennials for Shade and Part Shade, in the section Perennials for Part Shade in Moist Soil, as well as in our Gardening Guide on Native Perennials for Shade.
Better choices for that south-facing foundation bed might be found in the Gardening Guide for Drought Tolerant Perennials.