How we propagate our plants

We use different methods of propagation such as seed, cuttings, grafts and micro-propagation.

Seed

Many of our Species Rhododendrons are sown from wild collected seed. Where this is the case you may see a seed number in the plant name or description. This number records who collected the seed, and can be cross-referenced to the collectors' notes. New species are introduced by this method. We are always excited when seed collectors send us their precious seeds that they have collected from the remotest parts of the world. Alongside the seed number that they assign to their seeds, nowadays they list the GPS location of where the seed was collected from, (and yes they do write descriptions like “next to the second rock on the right”) and the date that they collected it. The number is preceded by their initials, thus identifying themselves.

Of course seeds can be collected from Rhododendrons that flower in your garden, and while these will not come true to their parent, it can be an exciting exercise. Rhododendrons are fairly promiscuous and they can be crossed pollinated by insects flying from one plant to another. To grow species or to propagate new hybrids, one has to carry out controlled pollination to avoid insect pollination. This process is best left to the experts! Seedling variation means that there can be differences from one batch of plants to another.

Seeds are collected in the autumn, dried breifly to open the seed pod, seived clean and then stored in brown envelopes in the fridge until we are ready to sow them. We sow onto moist spongey compost at 15C in December, and cover with polythene to help humidity. Germination usually takes 2 to 3 weeks in our Propagation glasshouse and then we give extra lighting to encourage growth before the light levels improve in spring. The whole process takes 3 years until your plant is ready in a 3 litre pot.

Cuttings

All our Evergreen Azaleas and Dwarf Rhododendrons are propagated by cuttings. Some of the tall hybrid Rhododendrons and the Deciduous Azaleas are much harder to root by this method. Timing of taking cuttings is crucial, and ranges from June to January to get the best rooting results. Most of our cuttings come from our own garden and trials area but we do occasionally get material from other large Rhododendron gardens, particularly if we want to introduce a new or different variety to our range. We are busy taking cuttings when the new plant growth has hardened but is still flexible. We have modern Propagation facilities with the latest automatic mist, humidity, heating and ventilation controls. You can try cuttings in a pot on a North-facing windowsill with a polybag over the top if you would like to have a go!

Grafts

As mentioned earlier some varieties of Rhododendrons are particularly difficult to propagate from cuttings and we get better results by grafting. The process is similar in that we collect cuttings but instead of planting them in compost, we graft them onto the rootstock of another Rhododendron plant during the autumn. In simple terms, we root Cunningham's White cuttings, and then make some accurate cuts to the base of that and match up the variety we want to graft on to it. By tying the two together with rubber bands, the 2 parts will fuse together forming a choice plant growing on the roots of Cunningham's White. We use Rhododendron Cunningham’s White as it is a reliable, disease resistant plant which rarely produces suckers from below ground. In the past grafted plants did have a bad reputation for throwing out suckers because R. ponticum was used as a rootstock, and in time some branches escaped and the mauve flowers became the dominant part of the plant.

Micropropagation

In other words, test tube Rhododendrons! Since about 1985, this method of propagation has proven to be successful, particularly for bulking up new varieties. Tiny pieces of cutting are rooted on agar gel in a laboratory, before being weaned into small cells of compost. Again, this is a useful method to propagate the varieties that are hard to root by conventional methods.