Caring for Bromeliads

It has become a tradition at the Exotic Garden that the first plants to be moved to their winter quarters are the Bromeliads on the evening of the last garden open day. This is not to say that they are particularly delicate or tender as in fact they are remarkably durable plants. You can never be sure when the weather will take a turn for the worse and as there are so many tender plants here we have to be prepared. If you only have a few tender plants, keep a close eye on the forecast and if it remains mild leave them be. Its always sad to have to dismantle the garden in its prime but there are too many cherished plants to take any chances. The hundred strong collection of Bromeliads take centre stage adorning the steps to the front door of the house to be admired at every pass. When the time comes for winter preparations to begin this seems as good a place as any to begin.

A selection of the Bromeliads displayed on the steps to the house. Deep purple leaves of Neoregelia sp., pink star shaped inflorescence of a Nidularium sp., spotted maroon and cream Bilbergia cultivar, bright red Neoregelia tricolour, bronze, narrow leaved Cryrtbergia rubra and the gold and green striped Bilbergia ‘Melon’.

Bromeliads are a diverse group of plants originating from tropical and sub-tropical regions of the Americas. The most common and ornamental Bromeliads are the rosette forming species capable of holding a reservoir of water in the vase formed by the tightly overlapping leaf bases. In their natural habitat they would be found growing as epiphytes high in the canopy of equatorial tropical forests. Here the roots serve primarily as anchorage, known as hold fast roots, and all the nutrients required by the plant are absorbed from plant and animal detritus which fall into the vase. It doesn’t rain continuously in the rain forests and their lofty location puts them in the searing equatorial sun. As a consequence they are remarkably drought tolerant and its important to bare this in mind when overwintering them in cool temperate gardens.

The deep purple almost black fluted vases of Bilgergia ‘Darth Vader’. These cylindrical species are from much more arid habitats, their shape serving to conserve water. Known as geophytes, unlike their arboreal cousins the can be found clinging to rocks and forming large terrestrial mounds.

Neoregelia ‘Tossed Salad’, one of the larger tank forming Bromeliads. These bruits form treetop reservoirs in the forests canopy harbouring arboreal crabs and tree frogs. Over time the can grow so large that the bring crashing down entire bows.

From May to October the collection of vase or tank forming Bromeliads are displayed outside in full sun. There are many cultivated varieties with striking colour variations and patterns which are intensified by placing in direct sunlight. The collection here are grown in terracotta pots in 100% bark chippings and throughout the summer months they’re watered regularly. Free drainage is important as the rosettes, although filled with water, can easily rot from the base if kept soggy. As low maintenance plants go they rank pretty high though when it comes to winter they certainly aren’t frost hardy. They will however tolerate much lower temperatures than their equatorial origins would suggest. The killer combination when overwintering most tender exotics is the combination of cold and wet together. As each plant is moved to the poly tunnel for the winter its vase is emptied out, any detritus is removed and any brown lower leaves and spent rosettes are cut off. They are placed on the bright side of the poly tunnel and left dry all winter, it couldn’t be easier. The tunnel here is heated to around 7C minimum, however on the coldest nights the temperature has dipped close to zero without incident. During the lengthening days of spring while there’s still a risk of frost but the strengthening sun is heating up the tunnel by day pay close attention to signs of drought stress. The leaves will begin to curl up along their length, loose their glossiness and begin to go brown at the tips. Little by little start refilling their vases until all risk of frost has passed and they can be returned to the garden.

Aechmea blanchetiana. This is one of the most stunning Bromeliads to grow and an perfect example of the importance of sunlight in developing the pigments in the leaves and thus their full character. A. blanchetiana, as below, has stunning gold to dark orange foliage. This specimen grown from a pup this spring has spent the summer in the filtered light of the poly tunnel shaded by other plants.

Aechmea blanchetiana. The more sunlight this plant receives the richer the colour. In tropical locations the foliage becomes almost red. This is an adaptation to prevent damage from solar radiation, akin to getting a tan. Over winter when light is at a premium there is no reason for the plant to invest in the pigmentation and so they revert to green.

The rosettes of Bromeliads are monocarpic, meaning they only flower once and then die. Often the spent rosettes persist for some time but eventually senesce as nutrients and vigour are diverted to new pups that form at their bases. The fading rosettes can be cut out taking care not to damage the newly emerging pups. Alternatively the new pups can be removed once they are one third the the size of the parent rosette. A sharp knife should should be used to get as close to the stem as possible. Plant these firmly in bark chippings, keep their vases full and place them somewhere bright and warm to establish.

The largest of the Bromeliads in the collection, this Aechmea is now at least four feet across. Bedded out in a jangly corner for the summer it will be dug up and re-potted in the autumn. Before lifting it is bound up by duck-tape to protect from the saw-toothed leaf margins and so it will fit through the door to the greenhouse. Despite its size the root system is comparatively insignificant and despite the annual it continues to thrive.

How to Build Your Own Living Wall or Vertical Garden

Liz, myself and the newly planted vertical garden.

A few years ago now, on a trip to Paris, quite by chance I came a cross a vertical garden or living wall created and installed by the French gardener and designer ‘Patrick Blanc‘. The plants are rooted into a thick hydroponics membrane through which a nutrient enriched solution trickles, pumped up from a reservoir at the base of the wall which keeps the plants fed and watered.

The vertical garden on the wall of the Musée des Arts Premiers Quai Branly in Paris.

I had often spoke with a friend of mine ‘Will Giles’ about how we could create a DIY version, looking at all the possible ways of supporting it, what to use as the membrane, how to hold it up, what to use as the reservoir and how to feed the plants among many other things. After a while we came up with a much simpler solution, as the best ideas always are. Do away with the expensive and intricate hydroponics and build a structure that is essentially a series of hammocks, a bit like a multi story window box. It may take a little bit of daily care to keep the plants watered and looking good but is much easier and cheaper to build.

It was while I was working at Urban Jungle hardy and exotic plants nursery that I had the opportunity to put the idea to the test. I had a rough idea of how the structure might work but no set figures to work from. I could see ‘Liz’ my boss and one of the owners of Urban Jungle looked a little apprehensive as I was attaching 12ft high pieces of timber to the edge of one of the pergolas in the middle of the nursery. Once the wall had taken shape and looked as if the monstrosity was going to work, apprehension quickly turned to plants. Once the wall was up and the pockets filled with compost we set about rounding up plants from the nursery and setting the out on the floor in front of the wall for planting, and then planted well into the night. The wall turned out to look not too bad and after a week or so, when the leaves had turned themselves up to the light, it looked pretty damn good. Many visitors to the nursery asked how it was built so here, at last, are the designs for the vertical garden. Sorry about the wait.

Planting the wall by headlight.

The wall is now coming up to its second season and has endured one of the coldest winters for years, where I’m shore the entire thing would have been frozen solid for several days if not weeks at a time. I’m no longer at Urban Jungle but have heard from Liz that some of the plants are now on the move and in a short time she will be able to see what had pulled through and what needs tweaking. Some plants were not hardy so there will inevitably be some gaps to plug. Liz is going to put up a post on Jungle Drums, the Urban Jungle blog,  in the coming weeks on the progress of the wall, what has worked, what hasn’t and the new plants that will fill the gaps. As soon as it’s up I’ll post a link.

HOW TO BUILD YOUR OWN LIVING WALL OR VERTICAL GARDEN

1) CHOOSE A LOCATION- Once the wall is planted and watered it will be very heavy so a suitable structure is needed to support the wall. If the base of the wall is resting on the ground and this is not a solid surface, place slabs under each of the uprights to spread the weight and prevent it from sinking into the ground. If the wall is not resting on the ground make shore the brackets used to hold the living wall to the supporting structure are strong to take the weight of the wall when saturated. If the supporting is a house or shed wall the structure should be mounted away from the supporting wall to leave a cavity and avoid causing damp problems.

2) ORIENTATION- The place we chose for the wall at Urban Jungle by chance faces east. This in my opinion is the best direction for it to face as it gets direct light up until noon in the coolest half of the day. If the wall was south or west facing more particular attention would have to be paid to watering and plants would have to be selected to tolerate direct light. Regarding watering, it is important to be diligent as anyone who has let a hanging basket dry out knows it takes a while to re-wet, and you cant dunk the wall in a bucket. North facing walls would require less attention but the constant shade will limit the choice of plants.

3) CONSTRUCTION- The wall at Urban Jungle was 12ft high, 7ft wide and build against a large pergola for support. I used three uprights made from 12ft lengths of 2×4 tantalised timber. The two uprights on the edge of the wall were attached to the uprights of the pergola with brackets and the middle upright stabilised by a post in the ground and two cross members. Each of the uprights was rested on a paving slabs to help spread the weight. The horizontal spars that support the planting hammocks were made from tile baton. Each spar was screwed in place with a little wood glue for extra support. The spars were placed 10cm apart. This made the pockets closemouthed together so that when planted not too much gaps are left but there is enough room to squeeze the root balls in.

How to build the timber structure that supports the wall.

4) POCKETS- Because the wall had three uprights there had to be two series of pockets as they cant cross the uprights. The pockets were made from heavy duty landscape fabric which needs to be about two and a half times longer than the height of the wall and about 20cm wider than the width between the uprights. Start by folding about 10cm in each side so the fold is facing the front and attach to the back of the top spar with staples or by screwing a second spar over it. Push the fabric in between the top and second down spar so it forms a pocket about 15-20cm deep. Place a few staples in the second down spar so the fabric doesn’t slip. This will not need to be as secure as on the top spar as the weight of the compost will hold each pocket in place. Repeat the process down to the bottom of the wall and securely attach the end of the fabric to the bottom spar.

How to attach the landscape fabric to create the pockets.

5) FILLING- We decided not to add any ingredients to the compost like pumice or perlite to reduce the weight as we were happy that the structure would support the weight. We mixed plenty of slow release fertiliser granules into the mix as there will be a large amount of plants in a relatively small volume of compost. We also added a quantity of swell gel to aid water retention. Fill the wall from the bottom pocket up so that each filled pocket rests on the one previous. Fold up the excess landscape fabric that was folded in on either side to prevent the compost from spilling out the end of the pockets. Each pocket should only be filled three quarters as the root balls from the plants will take up a proportion of the space and the soil level in the pocket  must be just below the spar so water can soak in and not poor off the wall.

The newly planted wall before the leaves have turned up to the light.

6) PLANTING- We set the plants out on the floor in front of the wall to create a design before we started to plant. Spacing will depend on the plants you use and the size of the plant used. Start planting from the top down. If you plant from the bottom up the lower plants will be covered with compost. Lay a sheet down bellow the wall as a lot of compost will be spilt. Make shore the plants are well watered before planting as many of the root balls will have to be teased apart and squeezed into pockets. Despite our planning we changed the design considerably while planting as it looked so different when vertical. Liz more so than other gardeners is a very impatient gardener so we planted a little closer than was probably necessary and plugged the gaps with Tradescantia cuttings, Spider plants and Begonia sutherlandii. These quickly grew and filled the gaps. We debated weather to use only evergreens but decided this would be too limiting on the design possibilities and would make the wall predominantly green. The down side to using deciduous or herbaceous plants was that the wall will look a little sparse over winter. We put a few dwarf Daffodils in the wall to see how they would fair. These wouldn’t hide the landscape fabric, but would add a splash of colour before the new shoots emerge.

7) WATERING- The wall will have to be completely manually watered. Rain will have little if any benefit to the wall other than slowing the rate at which the wall dries out, plus the leaves will arrange themselves like roof tiles shedding all the rain water. We didn’t get around to installing a trickle irrigation system and hand water the wall daily, sometimes twice if it is really hot and or windy. From autumn to early spring watering will be much less but still important. To install a trickle system there would need to be one trickle pipe along each pocket with dripper every 30cm or so. The dripper pipe would need to be the sort that delivers a specific flow of water rather than a simple leaky pipe as the bottom of the wall would receive more water than the top. The watering regime would have to be little and often to prevent the nutrients from being leached from the compost.

8) FEEDING- The slow release fertiliser we put in the wall was more than enough to see the plants through the first season with no signs of stress. The second and subsequent years are where attention is needed. Each perennial plant should have a hanging basket pellet pushed into the compost near the root ball. Any annual or replanted patches should have the old compost removed and replaced with fresh compost and slow release fertiliser. The old compost will be matted with the roots of perennial plants which should be carefully cut without cutting the landscape fabric. If a trickle system is installed a liquid drip feeder could be attached or if hand watered use an occasional folia feed.

Ingenious Bladderwort Trap

“What a wonderful and long-continued series of variations must have led up to the perfect ‘trap’ in Utricularia, while at any stage of the process the same end might have been gained by a little development of roots and leaves, as in 9999 plants out of 10.000!” Alfred Russel Wallace, from a letter to Charles Darwin dated  21st of July 1875.

Poly Tunnel Build

The many tender exotic plants which fill the borders of the Exotic Garden spend the fickle winters in a large poly-tunnel.  This video, filmed by Chris Ridley, captures its construction back in February 2012. With a bit of ingenuity the new tunnel was constructed over the old, smaller one then fit to burst at the the seams.