 Algerian ivy is an interesting species. It is useful as a ground cover in the juvenile form as it creeps along the surface of the soil, rooting as it goes. When it encounters a perceived supportive structure, such as a tree, a fence or the neighbor's old Volkswagen, it produces climbing stems that grip with root-like structures. When this growth reaches the top of the supportive structure and can climb no higher, shrubby adult growth with self-supportive stems appears and immediately begins to bloom and produce fruit containing seed. It developed this aggressive tactic to compete with trees endemic to its natural ecosystem but can easily adapt to a landscape situation.
Most vines climb for the same reason—to get to the top. Algerian ivy is typically employed as a ground cover and not permitted to climb. However, most other vines are expected to climb and are consequently often installed with garden structures such as trellises and arbors that may exploit their natural characteristics. Vines are generally useful for such purposes, but many can cause serious problems if not confined.
Vines climb by various methods. Some do not climb at all but are brambles that sprawl over supportive structures and other plants. Others grip with modified roots, specialized thorns or tendrils that are actually modified leaves. True vines climb with twining stems that wrap around anything supportive. Very few climb with "twining petioles," wrapping leaf stems around support.
Climbing roses, various berries and even bougainvillea produce long canes that do not actively climb but can be tied to supportive structures. For example, some of these types can emerge from the dense canopy of a cypress tree simply because the thicket of growth within supports any cane that passes through it. Canes or brambles are not as voracious as other types of vines but can become overwhelming.
Most vines that climb with tendrils are complaisant perennials. However, Boston ivy climbs with specialized tendrils that grip not by wrapping around support but by applying "suction discs." These discs are very difficult to remove and may take paint or stucco with them when they go. Modified roots of ivy or philodendron can likewise become attached to supportive surfaces. (Philodendron vines are rare in local gardens, but self-supportive philodendrons produce aerial roots that behave similarly.) Creeping fig is so voracious and the rooting stems are so damaging that it should only be used on reinforced concrete structures or where resulting damage is not a concern. It certainly would not be satisfied with merely the neighbor's old Volkswagen.
True vines lack destructive modified rooting structures or suction discs but include some of the most voracious species, such as wisteria. Although wisteria is very useful on arbors and trellises, it cannot be permitted to escape into trees or other structures. Supportive trellises or arbors should be substantial enough to endure constriction from expanding vines and to support mature vines.
Vine of the Week: Fern asparagus
Fern asparagus, Asparagus setaceus, is one of those rare vines that climbs by twining stems that partially unwrap as they mature but are then supported by small, sharp thorns. Vines are very slender and appear to be delicate but are actually tough and fibrous and can climb as high as 15 feet. The very finely textured foliage does not resemble any fern I am familiar with but somehow seems like it should be that of a fern. The very small leaves are actually modified stems known as "cladodes." The real leaves are not visible. Fern asparagus' very small white flowers and subsequent black berries are not common or remarkable.
A dwarf cultivar, "Nanus," does not climb as high, if at all, but typically forms denser growth near the surface of the soil. Fern asparagus is rather resilient and easily replaces itself if all growth aboveground is removed. It may actually be difficult to eradicate once established but fortunately never becomes too overwhelming.
Horticulturist Tony Tomeo can be
contacted at 408.358.2574 or at LGHORTICULTURE@aol.com.
|
Photograph by Shari Kaplan