Fertilizing Karl Foerster grass in containers *


Hello-Last summer we planted Karl Foerster grasses in 3 large containers on our condo terrace. We cut them in early April and happily we have significant new growth in all 3 containers. Should we fertilize the grasses now? And if so, what is the best fertilizer and ratio to use at this time? Many thanks- Dan


Thank you for contacting Toronto Master Gardeners.

Calamagrostis x acutiflora ‘Karl Foerster’, commonly known as Feather Reed Grass will grow to be about 4 feet tall at maturity, with a spread of 32 inches. It’s adaptability to both dry and moist locations makes it a good specimen for containers.

Ornamental grasses require relatively low levels of fertility. By keeping the level of nitrogen low, lodging or flopping over can be kept to a minimum. Leaf color and vigor are good guides to nitrogen requirements, based on growth response. If the previous year, plants were slow growing, small, with yellow color, add some fertilizer.

Application of one-quarter cup of 10-10-10 fertilizer per plant is sufficient. Apply fertilizer just as growth resumes in the spring. An application of a slow release fertilizer in the spring is enough to take care of the plant’s needs throughout the summer. Fertilizer should be watered in thoroughly.