JARS v63n2 - Dwarf Rhododendrons for Containers and Small Garden Spaces

Dwarf Rhododendrons for Containers and Small Garden Spaces
Ron Knight
Pender Harbour, British Columbia
Canada

Everyone has seen examples of gardeners who have over-planted a new bed, filling all the available space with cute baby shrubs and trees. For the first couple of years they look great, but after that the plants begin to grow into each other and their beautiful individual shapes are lost.

Enthusiastic new rhododendron collectors living on regular "city lots" often make the same mistake in their quest to display as many as possible of the plants they have heard the experts say are "the really good ones": R. augustinii , R. macabeanum , and the hybrids 'Lem's Cameo', 'Loderi King George', 'Sir Charles Lemon', etc. They purchase dozens of young plants in one and two gallon containers, placing them about 0.5 m (1-2 feet) apart throughout the beds and borders of their small garden. Unless some are moved, the space inevitably begins to look overgrown and messy as the plants reach their mature sizes.

Pruning to correct this problem is often ineffective because it destroys natural plant shapes. Wouldn't it really be better, right from the start, to plant very slow-growing specimens in small spaces, ones that will not later require drastic pruning or relocation?

Dwarf and semi-dwarf rhododendrons provide a perfect solution for homeowners with small garden spaces and for condo and apartment dwellers who rely on containers. (For the purpose of this article, dwarfs and semi-dwarfs are lumped together and are just called "dwarfs.") These miniature rhododendrons come from alpine ancestors with small leaves and a high tolerance to wind and sunshine. As a rough guideline, they reach one meter (three feet or less) in 10 years. Of course all rhododendrons keep growing after a decade but dwarfs do so at a very slow rate.

Most dwarf rhododendrons are evergreen, require minimal care, have showy flowers in a wide range of colors, and sport dense foliage that is attractive all year long. They are susceptible to few pests or diseases. Varieties are available that will bloom in each month from March through July in the Pacific Northwest. They look most attractive when given maximum sunshine, for example in a rock garden or a container on a south-facing patio. Many dwarfs will become leggy and less floriferous when planted in the shade.

Dwarfs need to be located as far away from plants with aggressive roots as possible. They coexist well with mosses but not with most ground covers. They prefer a covering of mulch over their roots, but not grass clippings, peat, or sawdust. Dwarfs, like all other rhododendrons, require acidic well-drained soil. A mixture of topsoil, mulch and peat moss works well. They need to be planted on a slight mound rather than in a rocky depression that may allow water to pool around their roots. On steep slopes, a dam of mulch or rocks should be placed on the downhill side of the plant so that water is channeled through the roots rather than over the top of the soil. Regular watering is essential during the summertime in the Pacific Northwest and a drip irrigation system is ideal both for dwarfs grown in containers and in the field.

In rock gardens, dwarfs need to be lifted and replanted when their roots have filled the available soil space. In containers, most dwarfs should be re-potted every second year. During the in-between years they appreciate a top dressing of compost. Light feedings with slow-release fertilizer or liquid plant food are also beneficial.

Dwarfs rhododendrons look spectacular when planted in groups. In alpine regions, they naturally grow that way to provide mutual protection from strong winds. Only some very early bloomers whose buds are susceptible to frost damage need any special winter protection in most garden settings. Minimal pruning is required for dwarf rhododendrons. Each year, however, it is wise to remove dead branches from under the leaf canopy. Deadheading is usually unnecessary; however, fussy gardeners may want to remove seed capsules that stick up above the leaves of certain varieties.

Unfortunately, most retail garden centers carry only a very small selection of dwarf rhododendrons, and usually all of these are hybrids. Dwarf species rhododendrons, although they are harder to find, are worth collecting because they often have superior foliage. Only specialty rhododendron nurseries are able to provide a wide choice of both dwarf species and hybrids.

Examples of interesting dwarf species rhododendrons are:

• R. campylogynum - The bell-like flowers, with long stalks, bloom early and come in a wide variety of colours.

• R. hanceanum 'Nanum' - Cream-coloured flowers and a compact growth habit make this an attractive plant.

• R. calostrotum spp. keleticum - It's deep reddish-purple flowers resemble pansies and like most dwarfs, it's good for bonsai use.

• R. kiusianum 'Komo Kulshan' - This selection of a native Japanese azalea has two-toned pink flowers.

• R. nakaharae - This creeper, with large flowers in shades of rose or orangey-red, blooms into July.

• R. saluenense - It has crimson-purple flowers with aromatic foliage that turns a burgundy colour in winter. It may bloom twice per year.

Among well-respected dwarf hybrids are those developed by Warren Berg. Examples are 'Ginny Gee' and 'Patty Bee', both Superior Plant Award winners, and 'Wee Bee', a cheery little rhododendron with pink and red flowers. Any of the Cox family's bird-name dwarfs such as 'Ptarmigan' and 'Wren' are also worth purchasing. Other good hybrids are 'Carmen', 'Creeping Jenny', 'Curlew', Ernie Dee', 'Lori Eichelser', 'Moerheim', 'Princess Anne', 'Ramapo', and 'Shamrock'. There are many more dwarf rhododendrons that will please container gardeners or those with small garden spaces. And the really good news from Peter Cox, a world-renowned rhododendron expert, is that the Pacific Coast region is "the nearest to ideal for most dwarfs."

Ron Knight is a member of the Vancouver Chapter and serves as the District 1 Director. His rhododendron collection is located at Caron Gardens in Pender Harbour, British Columbia.