Tasman Leader : August 22nd 2013
19 THE TASMAN LEADER, AUGUST 22, 2013 GARDENING Something in the air Novel plant: The air plant Tillandsia usneoides growing in Rarotonga. Follow some simple rules and growing air plants can be fun and rewarding. By STEPHEN MCCARTHY The plant pictured is Tillandsia usneoides, or Spanish Moss, to give its common name. This is another example of how misleading botanical common names can be, because it is neither a moss, nor is it from Spain, but it is a member of the bromeliad family from the Americas. Tillandsia is a large genus of about 550 species native to forests, mountains and deserts of central and South America. The thinner-leaved species like T. usneoides grow in wetter areas whereas the thicker-leaved varieties grow in places more prone to drought. The natural range of T. usneoides is from Virginia, in the US, south to Argentina. It will grow successfully outside its natural range as evidenced by this specimen photographed thriving on a huge grapefruit tree in the garden of a house we stayed at in Rarotonga. It is often seen in films set in the southern US, where it drips from nearly every tree and even hangs off power lines. Because it grows so luxuriantly it was used at one time in the USA for padding car seats, and as packing material, building insulation and mattress stuffing. Tillandsias are epiphytic plants, sometimes known as aerophytes or air plants, in that they do not grow in soil. They are not parasitic on the host plant, but merely use them for support, gaining moisture and nutrients in the form of dust, decaying leaf and insect matter through structures on the leaves called trichomes. They rarely kill the host but certainly can lower the growth rate by cutting down the light levels. They have the potential to be a pest in places like the Pacific islands because they would substantially alter the environ- ment in native forests once it became established. Tillandsias are grown in New Zealand as novel indoor or greenhouse plants and range in form from hanging fine-leaved plants, to stiff rosettes of pineapple-like foliage (pineapple is also a member of the bromeliad family). They can be attached directly to a support such as clean driftwood by wiring, staples or waterproof glue. The support should not be made of treated timber or anything containing copper, which is toxic to air plants. Plants need to dry out completely between waterings so anything which would hold water around the base, such as sphagnum moss, would induce rot.Many people mistakenly think that because they are known as air plants, Tillandsias need little or no watering. The way in which Tillandsias are watered is very important in the success, or otherwise, of growing these interesting plants. Although in the wild they stand quite long periods of drought the plants need water in the form of rain otherwise they are merely surviving and not actively growing. Contrary to popular belief the plants dislike stuffy, humid conditions, doing much better in areas with good air circulation. When grown as a house plant, Tillandsias should be watered two or three times a week by gently hosing or even completely immersing the plant or running it under the kitchen tap until the foliage is completely wetted, simulating a tropical rain shower. To discourage rot the plant should totally dry out within four hours of watering, so it is best to water these plants in the morning to allow them to dry completely before nightfall. After watering the leaves should feel stiff and when needing water they will feel softer and also be lighter in colour. We noticed this on the plant in the photo -- after rain the plant was greenish- grey as opposed to pale grey in dry conditions. Dehydration is characterised by the leaves being flaccid and wrinkled or rolled. Tillandsias tolerate a wide range of temperatures from near freezing to 40 degrees Celsius. In the Nelson area Tillandsias should be kept indoors during the frosty winters but can be put out- side once the day temperatures have risen and all danger of frost has passed. They need to be placed in light shade and remember to water them with a fine hosing a couple of times a week during dry periods. Bring them back inside once autumn approaches. When growing indoors do not place plants in direct sunlight because this is too hot and will scorch the foliage, but place them near a window for sufficient light. They do not grow naturally in deep shade -- no further than a couple of metres from a window is recommended. Artificial fluor- escent lighting seems to suit the plants well. Although not completely necess- ary, fertiliser will result in good growth. Tillandsias are intolerant of overuse of fertiliser and a sure way of killing plants is the indiscriminate use of artificial fertiliser. The advised application rate is at a quarter the recom- mended strength on the label and even then no more than once a month. Use a good water-soluble houseplant fertiliser applied with a foliage mister.
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