Karl Foerster feather reed grass (Calamagrostis x acutiflora ‘Karl Foerster’) is a popular ornamental grass, celebrated for its upright growth and elegant, feathery plumes. This cool-season grass offers year-round visual interest, with foliage transitioning from deep green to golden tan and flower stalks providing structure even in winter. Its popularity stems from its striking vertical presence and hardiness. This guide covers planting and cultivating this resilient grass.
Choosing the Right Site
Choosing the right location is foundational for the success of Karl Foerster grass. This plant performs best in full sunlight, needing at least six hours of direct sun daily. While it can tolerate some partial shade, especially in warmer climates where afternoon shade can be beneficial, too much shade may lead to less vibrant blooms and a floppier growth habit.
The grass is remarkably adaptable to various soil types, thriving in sandy, loamy, or even heavy clay conditions. Although it prefers rich, well-draining soil, it is tolerant of consistently moist and even wet environments, making it suitable for areas where other plants might struggle. Adequate drainage is important to prevent waterlogging, which can affect root health over time.
When planting multiple Karl Foerster grasses, proper spacing promotes healthy growth and air circulation. For a mass planting or a continuous screen, plants should be spaced 24 to 36 inches apart, measured from the center of each plant. If the goal is to allow for larger, more developed clumps that require less frequent division, spacing them up to 60 inches apart can be considered.
Preparing the Soil
Before planting, preparing the soil ensures a welcoming environment for root establishment. Loosen the soil in the chosen area to a depth of 12 to 18 inches, using a spade or tiller. This helps to break up compacted soil, allowing roots to penetrate easily and access water and nutrients.
Clear the planting site of any weeds, rocks, or other debris to prevent competition for resources and provide a clean bed for the new grass. Once loosened, incorporate a 2 to 4-inch layer of organic matter (compost, shredded leaves, or peat moss) into the top 6 to 8 inches of soil.
Amending the soil with organic material improves its structure, enhancing both fertility and drainage capabilities. This enriched soil provides a nutrient-rich foundation that supports vigorous root development and overall plant vigor, potentially reducing the need for immediate fertilization.
Planting Steps
Planting Karl Foerster grass is straightforward, best undertaken in early spring after the last frost or in early fall to allow for root establishment before extreme temperatures. Before planting, thoroughly hydrate the plant by submerging its root ball in water for about 10 minutes.
Dig a planting hole that is as deep as the plant’s container or root ball and at least twice as wide. This wider hole provides ample space for roots to spread into the surrounding loosened soil. Carefully remove the grass from its nursery container; if it is in a plastic container, gently tap the bottom and, if necessary, trim the bottom 2 inches of the root ball to encourage new growth.
Position the plant in the center of the prepared hole, ensuring that the crown of the root ball sits slightly above the surrounding soil level. This elevated placement helps prevent water from collecting around the crown, which can lead to rot. Backfill the hole with the amended soil, gently firming it around the base of the plant to eliminate air pockets.
After the hole is completely filled, water the newly planted grass deeply and thoroughly to help settle the soil around the roots. If the soil settles significantly, adjust the plant to ensure it remains upright and at the correct height, adding more soil as needed. This immediate watering is crucial for reducing transplant shock and initiating the establishment process.
Post-Planting Care
Immediate and consistent watering is important for newly planted Karl Foerster grass to establish a root system. Following the initial deep watering at planting, continue to water the plant every few days (typically every 2 to 4 days) for the first six weeks. This regular moisture encourages new root development, which takes about six weeks.
After this initial establishment period, watering frequency can generally be reduced to once a week, unless significant rainfall occurs. Ensure the soil and original root ball do not completely dry out during the first growing season. During periods of drought or extreme heat, more frequent watering may be necessary; check soil moisture by digging a few inches down.
Applying a 2 to 4-inch layer of organic mulch (shredded bark, compost, leaves, or straw) around the base of the plant is beneficial. Mulch helps retain soil moisture, regulate soil temperature, and suppress weed growth, contributing to a healthier environment for the developing root system.
Observe the plant for any signs of stress, such as flopping stems or crispy foliage, which often indicate a need for more water. Addressing these early warning signs promptly helps ensure the successful establishment and continued health of your Karl Foerster grass.