The Fern Leaf Buckthorn, Rhamnus frangula ‘Asplenifolia’, is a highly valued deciduous shrub or small tree celebrated for its unique aesthetic contribution to the garden. Its most distinguishing feature is the exceptionally fine-textured foliage, which consists of deeply cut, slender leaves that give the plant a delicate, almost fern-like appearance. This cultivar provides a soft, airy contrast to plants with broader leaves and offers visual interest throughout the growing season before turning attractive shades of bronze and yellow in the autumn.
Site Requirements and Initial Planting
The Fern Leaf Buckthorn performs well in a wide range of light conditions, tolerating full sun to partial shade. Full sun is defined as at least six hours of direct light daily. In hotter climates, a location that receives afternoon shade is beneficial to prevent the foliage from scorching, but morning sun is preferred for optimal growth.
The shrub is highly adaptable regarding soil but requires excellent drainage to prevent root issues. While it prefers soil that is moist and moderately fertile, it can tolerate both sandy and clay compositions and is not particular about the soil’s pH level. Constantly soggy or waterlogged conditions must be avoided. The Fern Leaf Buckthorn is remarkably cold-hardy, successfully growing in USDA Hardiness Zones ranging from 2 or 3 through 7 or 8.
When planting, the hole should be dug to be two to three times wider than the root ball, but only as deep as the root ball itself. Place the shrub in the center, backfill the hole with the excavated soil, and firmly press out any air pockets. Immediately after planting, water the area deeply and thoroughly to settle the soil around the roots.
Ongoing Care and Pruning Techniques
Once the Fern Leaf Buckthorn is established, its ongoing care focuses on consistent irrigation and strategic, minimal pruning. During the first summer after planting, the shrub should be watered deeply once per week, unless there has been more than one inch of rainfall. Established plants are relatively drought-tolerant but will grow best if the soil is kept evenly moist, particularly during extended dry periods.
Fertilization is generally light and infrequent for this cultivar. It is best to avoid fertilizing in the first growing season to allow the root system to settle. Moving forward, an annual application of a balanced, slow-release granular fertilizer, such as a 10-10-10 formulation, can be applied lightly in early spring.
Pruning requirements for the Fern Leaf Buckthorn are minimal, as heavy shearing can destroy its natural, fine-textured habit. The ideal time for any necessary pruning is in late winter or very early spring before new growth begins. The primary focus of pruning should be thinning the canopy to improve air circulation and removing any dead, diseased, or damaged wood. When thinning, limit the removal to no more than one-third of the overall shrub to preserve its graceful, weeping form.
Preventing and Treating Common Issues
The Fern Leaf Buckthorn cultivar is valued for its general resilience, showing no significant issues with pests or diseases. While the parent species of buckthorn can occasionally host pests like the soybean aphid, the ‘Asplenifolia’ cultivar is generally pest-resistant, requiring only occasional monitoring. If aphids or other common garden pests are observed, a targeted spray of insecticidal soap or a strong jet of water can provide effective, non-chemical control.
A significant benefit of selecting this specific cultivar is its non-invasive nature, which addresses a common concern with the species Rhamnus. Cultivars like ‘Asplenifolia’ are considered sterile or produce sparse, unviable seeds, meaning they do not spread aggressively into natural areas.
In colder climates, winter preparation involves applying a layer of organic mulch around the base of the shrub in late fall. This helps insulate the roots from extreme temperature fluctuations. If the plant exceeds its desired height over time, it can be maintained at a smaller size with routine trimming in the late winter.