Follow the Temperate unit as they complete the mammoth task of repotting the Sarracenia collections.
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 -
About the Tropical Nursery
The main functions of the Nursery are to:
- Form a back-up collection of tender tropical plants used to support science, display and education within the gardens. We supply plants for use in displays in the Main Kew conservatries, for festivals and events organised by the Foundation and the Directorate.
- Supply plants for education purposes to the Schools & Families department.
- Act as main propagation facility for the Princess of Wales Conservatory, Palm House and Temperate House as well as supporting the exchange of plants between Kew and other institutions and collections.
- Provide direct education in nursery techniques and the cultivation of tropical plants for the Kew Diploma course, Apprentice and Trainee programme, Internship and work experience programmes and visiting staff from other UK and overseas institutions.
- Support conservation by working with the UKOTs team undertaking propagation and cultivation protocols on targeted endangered species.
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