Renovation of rock

As gardens evolve and change, it is important to replenish plant stocks from existing specimens

Gardens are not static, unchanging things: beds become tired, plants get congested, or they may seed themselves around and take over in places. At RHS Garden Wisley, things are no different and from time to time the decision is taken to renovate specific areas. This gives us the rather exciting opportunity to channel our inner garden designer, by introducing new ideas and updating planting schemes.

The Alpine Team have been renovating several areas over the past couple of years, and recently they asked for our help from the Propagation team with increasing their stock of plants for the Rock Garden, one of the oldest areas at Wisley and the next in line for renovation.

Rooted Helianthemum cuttingsTheir first request was to increase numbers of a range of Helianthemum, also known as rock roses. These plants are native to the northern hemisphere and are predominantly found in Mediterranean regions, favouring free-draining soils and plenty of sun. We have many cultivars at Wisley, including favourites such as ‘Henfield Brilliant’, ‘John Lanyon’ and ‘Rhodanthe Carneum’.

Being evergreen, they are propagated by semi-ripe cuttings in late summer. Due to their need for free-draining conditions, we don’t put them on mist benches: instead, they are put on a heated pad on a bench and are covered with a plastic film to keep the atmosphere around them moist. We air them once a day to ensure botrytis and other moulds don’t take hold, and water them sparingly.

Semi-ripe cuttings take longer to root than softwood cuttings and the heat mat helps to speed things up. We took our cuttings in September and they are only just starting to root now so patience is key! If any have died off, they are taken out to avoid the others becoming diseased, and also pick off any dead leaves.

Taking Sedum and Zauschneria cutting by hand and putting them in a trayWe have also received propagation requests for individual beds in the Rock Garden, for plants such as Dianthus, Saxifraga, Campanula, Sedum and Zauschneria (right). When the lists of these plants arrive, I research how to propagate them and what aftercare is needed. Some requests come in for seed, which comes from either our own seed department or from specialist suppliers. Recently we have sown Pulsatilla and Meconopsis, which are now in our cold frame to receive a period of stratification (cold treatment) which will aid germination.

Once the research is complete, we arm ourselves with maps of beds, labels, plastic bags and a pair of secateurs and head off to find our target plants...

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