Ruperts Blog 1
Watering the tropical house. This is a change of scene, a journey without airmiles from the Walled Garden, where I spend most of my time, to Brazil. The Atlantic rainforest is where the bromeliads in front of me originate: they are in full flower and each makes a rosette of leaves, like a cup, where water collects. In the wild, a cold soup of insects, debris and bird droppings builds up here, like a sort of doubtful vichyssoise, nourishing the plant to a degree. Perhaps it is served lukewarm, given the benign climate of coastal Brazil.
It was in the Mata Atlantica, a strip of some of the most biodiverse forest on earth, that the bromeliads started to evolve. Not so deep or dark as the Amazon, the coastal rainforests were a stable and rich habitat, surprisingly consistent from north to south-owing to the influence of the Atlantic- and there still are some important areas around Rio de Janeiro and further down. But of what once grew, only about 5% is left. Recife, Salvador de Bahia, Rio de Janeiro, Sao Paolo are on this coast; immigration, settlement, agriculture, farms, coffee estates, eucalyptus plantations when the coffee became vulnerable to disease-all of these have reduced the Atlantic rainforest to a fraction of what it was.
Bromeliads are epiphytes
par excellence, never more at home than in the high canopy of rainforest trees, growing at times so luxuriantly that they become their own worst enemies and weigh down branches until the bough breaks. One or two species attain serious size: of the Brazilians,
Alcantarea imperialis is the largest, although not an epiphyte but a lithophyte. In flower, it will reach at least three metres tall and two metres wide. It grows on granite outcrops that are like ecological islands set in the sea of forest, rock formations known to geologists as “inselbergs”. Anyone who would like to know what an inselberg looks like has only to picture the Corcovado in Rio de Janeiro, where the famous statue of Christ the Redeemer stands.
Alcantarea imperialis is often self-pollinated, but it does have another pollinator: bats. Were it not for the bats, feeding and carrying pollen at night between these granite islands and from one population of alcantareas to another, the bromeliads would start to lose their genetic vigour.
Vriesea gigantea-no effort at irony here from the taxonomists here- is, however, a true epiphyte and hardly a midget, growing to a metre wide and sending up a two metre flower spike. I am not sure if we have this superb plant in the tropical house yet, but there is a lovely small alcantarea near where I am standing, which Ann has planted at the foot of a pandanus. Give it a few years and we shall see it what it can do.
Of course, more delicate bromeliads exist.
Tillandsia includes Spanish moss and other exemplary airplants, epiphytes which seem to live on, and in, the air. Hard to imagine Hollywood sets for backwoods Louisiana without trees eerily draped in Spanish moss-you can’t have the bayou without bromeliads.
Tillandsia usneoides also works quite well as an indicator in glasshouses. Where it is happy, the humidity for most orchids and epiphytes is about right. The genus is closely related to
Vriesea, though you might not guess it to look at them.
Considering the abundant watering rainforest plants are accustomed to, the bromeliads have been surprisingly successful at adapting to dry environments. Their original lifestyle, though, with its alternating downpours and desiccation, may have fitted them for this strangely well. The leaves of the epiphytic species have different combinations of leaf scales and leaf hairs, which allow them to regulate their intake of water. According to the environment and the species, their leaves can shed water like a duck’s back or absorb it like a sponge.
Many of these plants photosynthesize using the same biochemical technique as cacti and succulents-CAM photosynthesis-so that they thriftily hold onto water during the day instead of losing too much through transpiration. Effectively, through adapting to life in the branches of trees, the
Bromeliaceae have won two evolutionary trump cards for living in drier habitats: cleverly engineered leaves, and an ingenious biochemical variation on the usual method of photosynthesis.
It might be asked how much this has changed the fortunes of the bromeliads. The answer is, that it has allowed them to evolve to cope not only with drier habitats than the neotropical rainforest, but with some of the driest habitats in Latin America.
So tillandsias come to be among the few plants able to live in the fog deserts of Peru, blowing around, almost rootless, but capable of surviving.
Deuterocohnia grows in semi-desert conditions; and in the mediterranean climate zone of Chile, spiny puyas are found on arid north-facing slopes, growing in association with cereoid cacti. Terrestrial instead of epiphytic,
Puya includes some large plants. There is the huge
Puya raimondii (from outside the geographical areas this garden specializes in, so not cultivated here); it is the largest of the bromeliads.
Puya berteroniana is also impressive. The one in the Great Glasshouse decided to flower three years ago and sent out an inflorescence eight feet tall, bearing many dozens of flowers with petals the colour of an oil slick, and orange stamens inside.
Puyas are well defended. Savage incurving spines along the leaf margin are sometimes enough to trap sheep, which have been known to starve to death, unable to pull themselves free of the plant (in Chile, that is, not Wales). This macabre puya fact is mentioned on the video in our Great Glasshouse, but what the video omits to say is that puyas can also be painful for gardeners. Not to the point where you are likely to discover a colleague’s bleached skeleton in one, holding rusty Felco secateurs, but you are certainly guaranteed scratches from handling the plants.
It seems the only creatures not to find them a problem are Spectacled bears. They were shown tearing puyas to bits, to eat the spikes of flowers, in a recent David Attenborough series. This little fact of natural history was something I learnt from Martin last summer, while trying to get some potbound
Puya alpestris out of their containers to plunge in the Double Walled Garden. If there had been a Spectacled bear anywhere nearby, the puya, you sensed, might well have been given to the bear. They are uncompromising plants.
For gardens in England and Wales,
Puya alpestris and
P. chilensis are the hardiest of the genus. Even so, they cope with some cold but not too much wet at the roots, and it is perhaps more realistic to have them in pots, kept on the dry side over winter, somewhere cool and light, and then to stand them out for the summer. Fascicularias, cousins from southern Chile and Argentina, do not quite have the stature of the puyas, but will be tough enough to make an interesting piece of planting at the base of south or west-facing wall in drier areas. Or wetter areas? I am told reliably that there is one growing well in the crook of a horse chestnut at Picton Castle where it has been thriving for a decade.
Tropical bromeliads such as vrieseas take up a good deal of room, so that who intends to collect them should probably think about moving to Florida or Brazil as the affordable alternative to heating a large glasshouse in Britain, where such spaces are usually filled with small orchids, not huge bromeliads. The plants are appreciated for their landscaping value in the tropics and are quite often used in island beds or other bedding, but they have more potential than that: the great Brazilian designer of gardens, Roberto Burle-Marx, collected them and used them to effect.
Like orchids, bromeliads need only weak feeding (general purpose fertilizer diluted to a quarter-strength), and like orchids, the epiphytic species are happy to be tied onto cork bark and grown that way, so long as they have the humidity they need. They need to be tied on firmly. Nylon wire works, hidden with some sphagnum moss, but it is also possible to use thin strips from nylon tights.
For anyone who doesn’t have much room, doesn’t like orchids and does not want to move to Florida, but likes the idea of collecting bromeliads, airplants (tillandsias) are the space-saving answer. They flower spectacularly and you can spend quality time misting them (or trying to install a misting system). See them at plant shows such as the RHS Vincent Square events, and in botanical gardens, and then acquire some from a specialist nursery.
These are practical considerations. The most essential thing is perhaps that sense, between the pleasure you get as a gardener from looking after plants that are fascinating or beautiful, and imagining the plants in the wild, that the place these plants come from is almost endlessly rich in variety. Almost. The Atlantic rainforest is still, by all accounts, a botanical wonderland. Every effort should be made to save it.
Rupert Jensen
PS. Anyone who visits the Garden during the summer months is welcome to attend the Double Walled Garden talk, which quite often includes the story of William Paxton’s pineapple-Ananas comosus, the only edible bromeliad, and the Victorians’ fetish fruit. They were, almost certainly, grown in stove houses, which stood a few yards away from the site of our current trop house. They were difficult to ripen, desirable, valuable…and a twist of fate separated Paxton from his pineapple at the moment of a crucial dinner party…
http://www.sosmatatlantica.org.br/
