Propagation of plants
In a glasshouse
The Wakehurst Place nursery receives propagation requests from the gardens and woodlands units and from the Millennium Seed Bank. Generally the Millennium Seed Bank staff germinate seeds and pass them on to the nursery as seedlings to prick out and grow on. The gardens and woodlands staff either request seed and send it through the nursery to propagate, or request the nursery staff to collect cuttings or seed from plants currently within the gardens. There are a number of methods of propagation:
Seeds
Seeds are sown into a seed pan or plug tray. We use a mixture of 3 parts sieved peat-free compost to 1 part fine Cornish grit for most of our seeds (except those with specific requirements). If the seeds need covering we will then cover them with Cornish grit (if outside) or vermiculite (if in a glasshouse).
The seeds are checked and watered on a regular basis.
Germination takes place either in our propagation house (which is kept at 15°C – 17°C), or in cold frames. We often sow directly into the ground, especially with native species.
Once the seeds have germinated and are showing their true leaves we prick them out into small pots containing medium-grade, peat-free compost, leaving them for a couple of weeks until established. The seedlings are then moved to cooler lighter conditions to grow on, therefore avoiding etoliation.
Cuttings
We collect cutting material around the garden throughout the year. Cuttings are collected in the morning and put into a plastic bag with a splash of water. They are then brought into the nursery where they will be cut to the desired length and shape, and inserted into a seed pan pot containing 50% propagation bark and 50% Perlite, which is wetted beforehand. If there is a lot of cutting material it will be stored in the fridge throughout the day.
The cuttings are placed either in the propagation house, in outside raised beds or in deep pots, depending on the species and type of cutting.
Occasionally we undertake other propagation methods such as dividing, layering and grafting.
An example of a recent propagation is Dendroseris littoralis, the Cabbage tree. This is the plant that Robinson Crusoe’s role model, Alexander Selkirk, supplemented his diet with (by eating the leaves) when he was marooned on the Juan Fernández Islands in the eighteenth century.
Propagation Protocol
Family Compositae
Genus Dendroseris
Species littoralis
Common name Cabbage Tree
Propagation method/s Seed, cuttings, air layering.
Seed: germinated in the Millennium Seed Bank at 16°C for 12hrs of daylight and 12 hrs of night with 85% successful germination.
Cuttings: We tried cutting one of these tall single stemmed trees into hardwood pieces averaging 35 cm long and sunk them into a gritty peat-free compost mix. They were fully rooted within 6 months.
Also removed some of the top side shoots, these also rooted quickly and are growing nicely.
Air layering: Is currently being used at Kew to propagate from these plants.
Pre-treatments: None required
Establishment : Grown in peat-free, well-drained compost
Watering: Keep well watered during growing season
Pest and disease: Powdery mildew, Whitefly and red spider mite
Notes:
Air layering is where the stem is wounded and then wrapped in a moisture-retaining substance such as Sphagnum moss, then surrounded in polyethylene film. This encourages the wounded region to grow roots. When sufficient roots have grown from the wound, the stem from the parent plant is removed and planted.
Pest control: Ideally we use biological control, (benificial insects) which control the pests. We may introduce something like Encarsia formosa which is a parasitic wasp which targets glasshouse whitefly. We also use some chemicals if the bio control is not working. We do 2 sets of clean up sprays in late Autumn and early spring to clean up any over wintering pests and diseases, so that when we put our first set of bio control in they have the best chance of beating the pests.
