A number of ornamental plant materials are not fully exploited for their practical use in the landscape while also serving as ornamental fixtures. A myriad of shrubs to small trees exist that could readily be shaped into barrier plants/hedges while also yielding horticultural eye candy. Below are examples of two woody ornamentals valued by edible landscapers but often passed over for their usefulness as hedging material.
Hardy orange
Poncirus trifoliata has been in the U.S. for a number of years mainly as a past rootstock for the citrus industry. However, this small tree or large shrub provides many ornamental purposes, too. Landscapers can expect white, 1-inch, pleasantly aromatic flowers in March or April even on plants that have been significantly sheared the year before. The citrus-type flowers, delicate and dramatic, could be a selling point for spring season in the garden center. Fortunately, after flowers fade, there are more ornamental features to capture interest throughout the remainder of the growing season.
New foliage begins to unfurl and is the driving force behind the common name, trifoliate orange. The three-lobed leaves are about 2-3 inches long and wide, quite glossy and remarkably pest-free. I’ve never observed fall color for leaves but have rather watched some or all of the foliage drop green depending upon the severity of the winter season.
Round fruits, the shape and diameter of golf balls, quickly adorn the species after flowering ceases. Sour but edible fruits emerge green and ultimately ripen to yellow.
During a mild winter in USDA Hardiness Zone 7, trifoliate orange can be semi-evergreen (yet further south, evergreen). But even when it is completely devoid of leaves, there still is something to marvel over. The bright green, stout stems adorned with formidable 2- to 4-inch green thorns are quite attractive in their own right, lending bold winter interest. Furthermore, many of the fruits will persist into the winter months becoming “mummies,” but nevertheless interesting to observe considering what’s visually available otherwise.
In the landscape
Hardy orange remains overlooked for a number of functions in the landscape. For example, this Asian gem has great value as a small ornamental tree in even the most abbreviated landscape. It grows up to 15 feet high. In the northern edge of its growing range —Zone 7 or Zone 6 with protection—it may freeze back on occasion with time needed for the plant to regain its tree stature. Perhaps the greatest use is in the formation of formal or even informal hedges. Landscapers and consumers will find this plant quite malleable and amenable to virtually the harshest of pruning practices imaginable. Once hedged and given time to establish (one to two years max), Poncirus trifoliata is essentially indestructible short of an unseasonably harsh winter within its normal growing range. This species provides a durable hedge with boundaries which cannot be violated by people or animals due to its stout thorns. Consequently, hardy orange can define borders, prohibit foot traffic or lead visitors to a destination in the landscape.
In the nursery
No special cultural conditions are required for growing P. trifoliata. Full sun is best for superior form and performance of plants. Hardy orange will grow in both acidic to higher pH soils. Virtually no pests attack this species, but the real culprit to watch for is cold temperatures. Most failures in the nursery and landscape can be attributed to growing this plant beyond its cold hardiness range.
While short-term success can be realized in Zones 5-6, hardy orange needs to be in Zone 7 or warmer to remain vibrant in the landscape. Hedge applications can be particularly difficult in colder regions as some plants will freeze, while others remain unscathed. This “checkerboard” pattern of live and dead growth essentially ruins the hedge and requires considerable time (usually years) for the desired visual effect to rebound.
Propagate P. trifoliata by seed or softwood cuttings. ‘Flying Dragon,’ a long-time available selection, is a cultivar noted for its contorted/twisted branching habit. Selections for greater cold hardiness would be welcomed and would allow northern horticulturists to also grow and admire this ornamental citrus relative that can double as an ornamental oddity.
European filbert
Another species also overlooked for its multiple applications in the landscape is European filbert (Corylus avellana). While nut production is sought after in the Pacific Northwest and other areas, C. avellana and related filberts remain underutilized for specific ornamental purposes including their use as hedges, small windbreaks or other forms of barrier plantings.
Ornamental attributes
Filberts can offer a number of deliverables to the savvy landscaper in Zones 4 to 8.
Suitable as a large shrub/small tree and for hedging purposes, European filbert satisfies that craving for something different. Because of its tendency to grow almost in a thicket-type fashion, it lends itself nicely to hedging or even topiary type applications. Deciduous in nature, leaves emerge in late March to early April ultimately unfurling/expanding to 4-5 inches long and nearly as wide. Medium green, with showy “teeth” on the leaf margins, foliage of C. avellana provides ornamental appeal under a number of environmental conditions.
Flowers, particularly the male catkins, also bolster the plant’s ornamental stock. As cooler weather ensues, fall color may be red to yellow and can be quite showy for some specimens. Winter interest, albeit quite modest, exists given smooth to slightly furrowed gray bark/limbs as well as any nutlets that may persist into the dormant season.
Foliage withstands the scorching heat of the South but may benefit from partial afternoon shade which would also lessen the plant’s need for supplemental irrigation. Filberts, as far as ornamental performance is concerned, are not particularly fussy about soil type. I have yet to witness serious chlorosis even in high pH settings in Western Oklahoma. The main requirement for best growth is evenly moist soils. Plants will not thrive in xeric nor chronically wet soils but rather will perform admirably under average landscape settings.
This nut-producing plant is rarely utilized or thought of for the purpose of hedging in the U.S., but is a remarkably resilient species that deserves greater recognition for its utilitarian value in the modern landscape. Filberts have been shunned by some due to their predisposition toward suckering and even weedy-type growth habit. However, when used in the landscape, mowing and other activities will suppress any unwanted growth outside of desired boundaries.
Left unpruned as a specimen, expect C. avellana to develop as a large multi-stemmed shrub, sometimes small tree reaching 15 feet tall and 10-12 feet wide. The densely limbed species also provides shelter for birds and should be touted as a wildscape candidate in the retail nursery.
For the grower
Diseases and insects are possible, although C. avellana remains remarkably pest-free and will not require heroic pest control measures to satisfy growers’ aesthetic standards.
Once growers familiarize themselves with European filbert, they will quickly identify multiple attributes and uses to tout when promoting this plant that seemingly “has it all.”
Several cultivars for C. avellana and its relatives exist based on nut production, growth habit, foliage color, etc. Harry Lauder’s Walkingstick, without question, is the best known and perhaps longest available cultivar in the trade. It is only one of many other exciting mutations and variations (budded on seed-grown understock) available for experimentation.