Tropical Nursery blog

The genus Sarracenia comprises a number of carnivorous species that grow in the marshes and bogs of North America. Some are under threat from habitat destruction as many of the species have a very limited range.

Here at Kew, we have a relatively good representation (241 accessions, giving us a total of around 800 plants) of the genus, you can see them on display in the Rock Garden and the Princess of Wales Conservatory. In recent years they have become increasingly popular as they have been used for their striking pitchers in the RHS Chelsea Flower Show and have had coverage on the BBC Gardeners World show.

As far as cultivation at Kew is concerned, they have herbaceous rhizomes, they love to sit in water during the spring and summer when in growth, and they really like insects! I’ve seen some of our larger specimens that we keep outside in water filled tanks almost full to the brim with partially digested bodies.
 

Kew Diploma student Ben Houston working on an accession of Sarracenia minor (Image:  RBG Kew)

Potting is undertaken once every 2-3 years in March/April as they really like to be constricted in their pots. Sarracenias are one of the only collections that we still use peat for. We have tried our usual coir based potting mix but these plants really reacted badly to living in that medium. Currently we are doing trials with other peat free mixes and we are committed to finding an alternative for them. Our mix is 60% perlite and 40% peat; we are trialling a range of alternatives, from pure Seramis (expanded clay particles) to finely chipped bark.

First, the previous years brown pitchers are removed and the plant is taken out of the pot. The rhizomes are cleaned of old leaves, the spent compost is shaken off and the plant is checked for pest. If the rhizome is long and unbranched, the tip is removed to encourage it to send out side buds and become a clump. We use square pots for this collection; you can get more into the tanks this way and they provide a stable base on a windy day when they are outside. The clean rhizomes are potted into clean pots, with the rhizome at the back of the pot, facing into the center, so that as it grows the branching rhizome will fill the pot. We try to put the plants into as small a pot as possible, and we firm the compost really well. This way they will become constricted quickly and they will have a solid base from which to produce large pitchers. The plants always sulk for a season after potting, so we expect to see the fruits of our labour next summer!
 

The finished product, ready to go outside for the summer (Image: RBG Kew)

This is our fifth day of potting and we should be finished tomorrow, the collection is looking healthy and clean, and the tanks are all given a good clean as they are emptied. It always brings a smile of satisfaction to the faces of the team when we finish a batch and the plants look fresh and happy in their new homes.

- Nick -

Related links

• More posts like this one - Potting with coir

Nymphaea ‘Arc-en-ciel’ is an unusual day-blooming waterlily. Its multi-coloured leaves range from mid-green, to pink and dark red, often looking like it has been ‘tie-dyed’. Several waterlilies have blotches, but this is the only one that is variegated in this distinct way.

The colourful, marble- patterned foliage of Nymphaea 'Arc-en-ciel' (Image: Perry Slocum)

'Nymphaea' is Greek for water nymph and 'Arc-en-ciel' is French for rainbow (literally 'Arc in the sky'). This waterlily has broadly ovate to rounded floating leaves which can reach 25 cm in length and 12 cm across. It has a distinct cleft at the base of each leaf. Nymphaea ‘Arc-en-ciel’ produces white to pale pink star-shaped flowers, with yellow stamens. This unscented, hardy cultivar is considered to be relatively slow growing; an excellent plant choice for a small, sheltered pond or even for an indoor pool.

History of Nymphaea 'Arc-en-ciel'

Nymphaea 'Arc-en-ciel' (Image: Kit Knotts)

Little is known about this cultivar (particularly in terms of its parentage). Indeed, it was thought to have disappeared from cultivation. That changed when waterlily enthusiast Philip Swindells came across one that had no label while visiting Denver Botanic Gardens. He correctly identified it as Nymphaea ‘Arc-en-ciel’ as he had seen it a decade earlier in Europe before it disappeared.

Nymphaea ‘Arc-en-ciel’ has added significance as this waterlily, like many others, is inextricably linked with Joseph Bory Latour-Marliac (1830–1911). Marliac was one of the first to hybridise waterlilies, opening his French nursery in 1875. He introduced many new colours and forms. Sadly, Marliac’s ‘secrets’ of hybridising died with him, but he developed about 70 first-class Nymphaea hybrids, many of which are still popular, such as Nymphaea ‘Marliacea Rosea’, N. ‘Marliacea Chromatella’ and N. ‘Marliacea Carnea’.

In 1889, Marliac presented his collection to the World Fair of Paris; the same year that the Eiffel Tower was completed. Installed in the water gardens in front of Le Trocadéro, his hybrid waterlilies caused a sensation and won first prize in their category. They also caught the eye of impressionist painter Claude Monet. The exhibition inspired him to create the water garden in Giverny, as well as around 250 of his trademark oil paintings.

Cultivating Nymphaea 'Arc-en-ciel'

Waterlily tanks in the aquatic zone of the Tropical Nursery (Image: RBG Kew)

N. ‘Arc-en-ciel’ has been growing in the aquatic zone in the Tropical Nursery in tanks that are heated to 21˚C. Above the tanks are supplementary lights which not only increase the light levels in the zone but can also extend the day length. The temperature of the zone ranges from a minimum of 18˚C to a maximum of 22˚C. The evaporation from the tanks keeps the humidity in the zones quite high. The waterlilies are potted into loam. Crocks are used at the base of the pot and then topped with grit, which prevents the loam from escaping when submerged into the water. This cultivar is propagated by dividing the plant.

N. ‘Arc-en-ciel’ has been on display to the public in the small pond on the west side of the Princess of Wales Conservatory.

- Sam -

"In 2005, the Montserrat National Trust created a new botanic garden, providing a resource for the islanders and an attraction for overseas tourists. The botanic garden not only contributes to education and training for children and other residents of Montserrat, but it also undertakes scientific research into the island’s ecosystems and assist in their conservation."
(Colin Clubbe, UK Overseas Territories)

In my last blog I told you about my expedition to Montserrat, seeing the endemic and critically endangered pribby (Rondeletia buxifolia) growing in the wild. The Montserrat National Trust recognised the huge potential of pribby; using it as a native hedging plant around the new botanic garden’s boundary; choosing this endemic species over introduced exotic species such as Ficus.

Whilst on the Caribbean Island, Stewart Henchie (former Head of the Hardy Display section at Kew) and I helped to construct a shade house and misting unit at Montserrat National Trust’s newly built botanic garden. My colleague, James Beattie, visited later to provide horticultural training in propagation and collections management. Stewart had previously been helping implement the design, layout and horticultural organization of the new garden in co-operation with the Trust.

The Montserrat pribby growing in the Tropical Nursery, Kew

With specimens of pribby brought back to Kew, the Temperate Unit worked in collaboration with Marcella Corcoran from the UK Overseas Territories (UKOTs) team in Kew’s Herbarium, to put together a guideline sheet for its cultivation.

Trials carried out in the Temperate Unit began identifying the most appropriate compost, temperature, humidity and watering regimes that would successfully produce germinating seed and seedlings. The reason to develop best horticultural practices was not only to increase the numbers of this rare plant but also to share our findings with the Montserrat National Trust and other partners to enable them to conserve the species better.

The dainty, orange inflorescence of the pribby
 

- Nick -
 

The volcano in the Soufriere Hills, Montserrat (Photograph: P. Griggs)

One in five of the world’s plant species is threatened with extinction.

One of the many critically endangered plants that we look after here at the Tropical Nursery is the pribby (Rondeletia buxifolia). Pribby is restricted to one specific area in the north of this beautiful Caribbean Island: the Centre Hills. This plant species grows in dry forest and scrubland, and low altitude moist forest. Pribby generally prefers marginal habitats, particularly along forest edges and in forest glades.

Rondeletia buxifolia in flower (Photograph: P. Griggs)

In the mid-nineties Montserrat and its people experienced a devastating natural disaster. The dormant volcano in the Soufriere Hills erupted, burying the capital, Plymouth. Many of the inhabitants were evacuated to the UK (Montserrat is a UK Overseas Territory), and the remaining population moved north, out of the exclusion zone and away from the volcano. As many people moved into the area around the Centre Hills, pressures on the habitat of the pribby sparked a major drive to conserve it.

I first saw pribby when on a bursary trip helping Stewart Henchie (former Head of Hardy Display at Kew) and the  Montserrat National Trust set up a new nursery and botanic garden. The previous one was buried under six metres of ash following the volcanic eruption. After several weeks shifting earth and sweating under the tropical sun, the head gardener Mappie took me out into the forest. On the way up Katie Hill, I got my first glimpse of this critically endangered plant, surrounded by Heliconia, Begonia and palms in verdant tropical forest.

Montserrat Hills (Photograph: P. Griggs)

Little did I know that five years later this plant would be in my care back at the Tropical Nursery at Kew. I monitored it closely, learning every aspect of its growth. In 2008, I was lucky enough to see the pribby flower; this was the first time these flowers had been seen outside Montserrat. Many of the plants continue to bloom producing cream, yellow and orange flowers.

It is especially poignant to write about this plant today as we have recently congratulated Stewart on his retirement after 40 years of service to Kew.

- Nick -

--------------------------------------------------------------------------------------------------------------------------------

Useful links

• Rondeletia buxifolia species profile
• Science Directory  - ex situ collection
• Science Directory - Montserrat Centre Hills project
• Montserrat online herbarium

In March 2010, I was asked to design a dry tropical display for one of Kew’s iconic beds for the summer. I saw this is as a great opportunity to show the public the intriguing forms of some of our cacti and other succulents. These specimens are normally kept “behind the scenes” in the Tropical Nursery. The bed is situated at the north end of the Broadwalk, to the west of the Orangery; this high footfall area would allow many of Kew’s summer visitors to appreciate these unusual and often overlooked plants.

The circular bed at the north end of the Broad Walk

I hand-picked the individual specimens to ensure that there was a good selection of forms, shapes and sizes. Many succulents have a globular or hemispherical shape; this maximises the volume available in which to retain water. I chose to have a clump of one my favourite cacti species: Echinocactus grusonii. It is often called the “golden barrel” or, more unkindly, “mother-in-law’s cushion” due to it’s striking round shape and bright yellow spines.

It was the focus of an intensive rescue effort in Mexico in the 1990s when its primary habitat was due to be flooded after the construction of a major dam*. As such, it is one of our “conservation plants”. Few remain in the wild today, although conservation work in botanic gardens and nurseries in Mexico and the US has made this cactus one of the most popular in cultivation.

 A clump of "golden barrel" cacti in the succulent display

I transported the plants with help from a Kew Diploma student and an apprentice. Handling cacti can be tricky, so we used a tractor, coir matting, bamboo canes and even barbeque tongs to protect ourselves from the sharp spines. We also wore gloves, leather gauntlets and safety goggles. Before planting, we laid out all the plants on the bed to get the position just right (I realised that I wasn’t going to be too popular if I kept changing my mind about their positioning).

The Dry Tropics team apply the gravel

To prepare the bed, we put down a hard-wearing, polypropylene groundcover sheet. This helps suppress weeds, and also separates the soil from the gravel that we would use as a top dressing. We plunged a few of the larger, more upright specimens straight into the ground while still in their pots. These included the 1.5m high Echinopsis and the tallest Haageocereus x espostoa. We planted the rest of the plants directly into the topsoil of the bed. Once we had finished planting, we shovelled a thin layer of gravel across the surface, which provided a great foil to their structural forms.

The completed display in June 2010

The succulents seem to have responded really well to the prolonged warm summer and wet August, colouring up nicely, producing extraordinary flowers and putting on lots of new growth. As autumn approaches, we will return them to the protected conditions of the nursery before colder, wetter weather can do them any damage.

This display will end on the 19th September. The bed will then be returned to a more traditional bedding scheme in keeping with the Palm House parterre for winter. Given the chance to create another dry tropical display, I would use Echeveria cante, Agave attenuata and the stunning Agave bracteosa. This spineless and toothless plant has bright-green foliage and is often mistaken for an Aloe.

Not only should it turn a few heads, I might be a bit more popular with the team for choosing more tactile plants.

Sam Crosfield

* Reference: Echinocactus grusonii, United States Botanic Garden, no date, http://www.usbg.gov/plant-collections/conservation/Echinocactus-grusonii.cfm