Rhododendron yakushimanum or Yaks are they are often called are one of the more interesting Rhododendron species.
This is a really good compact rhododendrons is the species and it has many hybrids. A low growing plant rarely reaching more than 1m and usually smaller this truly is a dwarf rhododendron.
They have wonderful flowers, and are perhaps the neatest growing rhododendron species, however the combination of flowers and foliage is what makes them such a great plant.
Cinnamon coloured fur or indumentum on the underside of the leaves is not only attractive but it also protects the plant from spider mites and other insect pests.
If we wish to be correct this should be Rhododendron degronianum subsp. yakushimanum, as like many it has been reclassified recently.
The leaves are lance shaped with downward curving margins. The felt-like covering on either side helps them survive in more sun and warmer climates than some other species.
They come from the island of Yakushima in Japan, and form mountainous areas. This is a sub tropical island, so they are also used to warm temperatures.
The species itself is mound forming, dark glossy green leaves, slightly downwardly curved at the edges, with that Cinnamon indumentum on the underside.
New foliage is also blessed with a covering ofsilvery tomentose (short matted woolly hairs), the flower buds are pink opening to a clear white.
So Rhododendron degronianum ssp. yakushimanum ‘Yaku Angel’ (pictured right) is a good example of a modern cultivar. And as a group, the cultivars are often referred to simply as ‘Yaks’.
Although R. yakushimanum is a varied species in its natural environment it does have a number of desirable characteristics which have made it a favourite plant with hybridisers both in Japan and in the UK in particular.
Firstly its bushy habit, it is naturally low growing and is slow as well. It is an ideal plant for gardeners who are looking for a long term solution, rather than a ‘quick fix’. Because it is a little slow, advanced specimens will not be cheap, however they are certainly worth the money in many cases.
The foliage emerges a silvery felty white, most attractive, before darkening. The hairs are for a purpose, they lessen moisture loss and also protect from both cold and heat, as well as insect pests. So a Rhododendron that is sun more tolerant and a naturally smaller growing form gives R. yakushimanum and some of its cultivars great garden appeal.
How to grow Rhododendron yakushimanum – Basic Care
Being from mountainous areas these are a rhododendron that will tolerate cold winter and although they will take more sun than many other rhododendrons they are best when grown in afternoon shade especially in warmer climates. 18 -25°C in summer is ideal
Although Rhododendron yakushimanum seem to tolerate a little more sun than other species, a position in semi shade, or at least protection from hot afternoon sun is desirable. A humus rich moist soil is best. Little to no pruning is required.
- Soil needs to well drained but moist and slightly on the acidic side.
- Planting – Being shallow rooted be careful to plant then at the same depth that they were in the container. A good layer of mulch, leaf litter or better still leaf mold is ideal protection for the root system.
- Watering is best done by a deep soaking rather than frequent light watering. The combination of mulch, watering and afternoon shade provides ideal conditions.
- Fertiliser can be applied after flowering in spring, use a cammelia fertiliser, before renewing mulch.
Ongoing Care
- Well drained humus rich moist soil
- Mulch around plants to maintain a cool root run
- Best in dappled shade and a frost free position
- Pruning is generally not required, however you can tip prune after flowering to help maintain a bushy habit.
Rhododendrons are a shallow rooted plant and as such do not like deep or heavy mulch as this tends to suffocate the root system. A light cover of open mulch is preferable.
In a good soil most Rhododendrons require little to no fertiliser, they certainly do not require lots of high nitrogen types of fertiliser.
When establishing use a liquid seaweed fertiliser for the first two years and then a low nitrogen general purpose fertiliser every 2 years.
Pruning Rhododendron yakushimanum
Generally not required as these are neat compact plants. Deadheading after flowering is recommended for appearance and also concentrating energy back into the plant.
Any errant shoots can be pruned back if needed.
Look carefully at the base of the flower head and you will see new buds forming, use secateurs to snip the flower head off above this junction.
Rhododendron yakushimanum Varieties
Rhododendron yakushimanum has now been renamed as Rhododendron degronianum subsp. yakushimanum and it has only been widely cultivated since the late 1930s.
As well as the species itself, it is the so called “yaku hybrids” or “yak hybrids” that have become popular with gardeners around the world.
Rhododendron yakushimanum ‘Koichiro Wada’and Rhododendron ‘Hachmann’s Polaris’ are two well known varieties. However the seven dwarf hybridised by Percy Wiseman, at Waterers Nursery that really brought these plants into focus.
The species itself is is variable, low growing to around 2m in height, the hybrids are not all so small, 1.5m to 3m. Grumpy would be the lowest growing, Bashful a little taller, and Hoppy (Happy) taller to around 2.5m.
The variation in the species is due mainly to the different altitudes where they are naturally found.
More recently
Hans Hachmann Rododdenron yakushianum in northern Germany has taken hybridisation of R. yakushimanum to the nest step with many outstanding cultivars including, ‘Kokette’, ‘Fantastica’ and ‘Rendezvous’.
Landscaping uses
With a naturally smaller and more compact growth habit, Yakushimanum rhododendron types are suited for planting closer to the front of the garden border, and also in smaller gardens.
You could grow them in a small courtyard, in containers, on a patio or in orange of situations where larger types are not suited.
Rhododendron yakushimanum is available from the following nurseries
125 Palmer Rd Jindivick 3818
Open Thursday - Sunday 10am - 4pm
Specialising in growing and selling Rare and Unusual Trees, shrubs Perennials Bulbs and Climbers, a unique nursery with amazing stock.
www.muskersbroughtonhall.com.au