Alder buckthorn (Frangula alnus 'Columnaris')
Frangula alnus 'Columnaris' is a fastigiate deciduous shrub, known commonly as Alder buckthorn, prized for its upright habit and use as a narrow screen.
Complete Plant Information
Overview
Frangula alnus ‘Columnaris’, or Alder buckthorn, is a distinctive cultivar valued for its strong, narrow, fastigiate habit, making it an excellent choice where vertical structure is required in the landscape. This deciduous shrub maintains a compact form, often reaching 12 to 15 feet tall but only spreading 3 to 4 feet wide. Its glossy, dark green leaves offer consistent summer color, though fall foliage is generally unremarkable.
A low-maintenance selection, this variety fits well into average garden settings, provided it receives medium moisture and adequate sun exposure. While Alder buckthorn provides small, whitish-green flowers in late spring and summer berries attractive to birds, its main functional benefit is its upright silhouette, suitable for formal hedging or as a narrow accent.
Gardeners appreciate the utility of the Frangula alnus ‘Columnaris’ shape, which allows it to function effectively as a nearly columnar privacy screen or tall hedge. Despite its usefulness, gardeners should be mindful that the species plant can be invasive in certain regions, so checking local regulations before planting this cultivar is advisable.
Fast Facts
- Plant Family: Rhamnaceae
- Plant Type: Deciduous shrub
- Hardiness Zones: USDA Zones 3-7
- Size at Maturity:
- Height: 12-15 ft
- Spread: 3-4 ft
- Bloom Time: May to June
- Bloom Description: Whitish green
- Sun Exposure: Full sun to part shade
- Water Needs: Medium
- Maintenance Level: Low
How to Grow
Planting Frangula alnus ‘Columnaris’ is best achieved in spring or fall when the soil is workable. Ensure the location has average, well-drained soil, though the Alder buckthorn is quite adaptable once established. This cultivar thrives in full sun but handles partial shade gracefully. When planting for a hedge, spacing plants 24 to 30 inches apart will help achieve a dense screen that can eventually be pruned.
Care for this shrub is minimal, fitting its low-maintenance designation. Provide medium water, especially during dry spells, as consistent moisture is preferred for optimal growth. Fertilization is rarely necessary in fertile garden soils. Pruning is mainly reserved for shaping hedges; these can be cut back every one to two years to maintain a smaller stature if desired, perhaps keeping them closer to 3 or 4 feet tall.
Be aware that while the species can self-seed, propagation for this patented cultivar is best achieved through cuttings to ensure the upright characteristic of Frangula alnus ‘Columnaris’ is retained. In areas where it naturalizes easily, monitor seedlings to prevent unwanted spread onto neighboring properties or natural areas.
Landscape Uses
The primary appeal of this plant lies in its ability to provide strong vertical accents without excessive width. The dense, erect growth of Frangula alnus ‘Columnaris’ makes it an outstanding choice for narrow privacy screens or as formal flanking elements near entryways where space constraints limit wider shrubs. When used as a hedge, it responds well to regular shearing every one to two years to maintain a formal line, or it can be left slightly looser for a more natural, though still narrow, appearance.
Although its suggested landscape use includes naturalizing, gardeners seeking a more formal aesthetic should utilize it near foundations or as sharp vertical border markers. For companion planting, pair it with lower-growing perennials or ornamental grasses that contrast its deep green foliage in the summer. Because the species can spread aggressively, avoid planting it near ecologically sensitive areas unless rigorous pruning is guaranteed.
Standout Features
Flower Qualities
- Insignificant
Noteworthy Characteristics
The Alder buckthorn (Frangula alnus) earns its common name because it often grows near alders in moist soils; the cultivar ‘Columnaris’ is specifically noted for its fastigiate shape, growing 12-15 feet tall but remaining narrowly compact at only about 4 feet wide. Its growth habit features erect, laterally compact, and sometimes twining branches, a characteristic that secured U.S. Plant Patent PP1,388 for the cultivar when it became popular in the 1950s. The dark green leaves hold their color late into the season, though significant fall color development is uncommon, and the flowers attract beneficial bees before yielding fruits that birds happily consume.
Tolerances
- Adaptable to a variety of soils
Potential Problems
Pests that may occasionally bother Frangula alnus ‘Columnaris’ include Japanese beetles, specific caterpillars, and scale insects, which can typically be managed with targeted horticultural oils or insecticidal soaps. Root damage from nematodes is also a possibility in susceptible soils, demanding good drainage management. Furthermore, watch for common fungal issues such as cankers, leaf spots, and rust, especially in humid conditions; ensuring good air circulation when planting helps mitigate these infections.
Frequently Asked Questions
What hardiness zones is Alder buckthorn suitable for?
Frangula alnus ‘Columnaris’ is cold-hardy and suitable for USDA Zones 3 through 7.
How large does Frangula alnus ‘Columnaris’ grow?
This cultivar typically matures between 12 to 15 feet in height, maintaining a narrow spread of only 3 to 4 feet wide.
What sun exposure does Alder buckthorn need?
It performs best when situated in locations receiving full sun, but it tolerates and grows well in areas with part shade.
When does Alder buckthorn bloom?
The inconspicuous, whitish-green flowers of the Alder buckthorn appear during the period spanning from May to June.
Conclusion
The Frangula alnus ‘Columnaris’ provides invaluable vertical structure for structured hedging or as a narrow specimen plant, offering reliable form with low maintenance requirements. Whether you need a modest privacy screen or a formal accent, this Alder buckthorn cultivar delivers year after year. Confirm your local zoning laws regarding this species and plan your installation during the optimal planting seasons of spring or fall.
Companion Planting
Selecting companions for Frangula alnus ‘Columnaris’ should focus on plants that appreciate similar medium moisture levels and tolerate the transition from full sun to part shade. Because this buckthorn is extremely vertical, pairing it with mounding or spreading groundcovers creates excellent textural contrast. Consider low-growing, fine-textured sedges (Carex species) or creeping phlox to soften the base near foundation plantings.
For height contrast in an informal border, plants that offer vibrant fall color—a feature lacking in the Alder buckthorn—make superb partners. Try using plants like native astilbes or contrasting deciduous shrubs that provide early spring bloom, such as smaller varieties of serviceberry, ensuring they are planted far enough away to allow the narrow habit of the Frangula alnus to remain uncrowded.
Wildlife Benefits
While the mature shrub itself is structurally beneficial for shelter, the flowers of Frangula alnus ‘Columnaris’ are notably attractive to early-season bees foraging for nectar in May and June. Following flowering, the plant produces small berries that progress from green to red and finally to dark purple by July.
These berries are highly sought after by various native bird species, which in turn aid in seed dispersal across the wider landscape. Gardeners focused on attracting and supporting local bird populations will find the fruit production of the Alder buckthorn a significant ecological advantage, balancing its formal landscape appeal with ecological service.
