Blue Diamond Rhododendron

There are many pleasures to be had from growing rhododendrons. The most obvious is the amazing garden display you will have from April to June when these magnificent shrubs are in bloom. In many minds they are all plants with big, leathery leaves and large heads of flowers. But the group is much more diverse than that, encompassing tall, tree-like plants and ground-hugging creepers, with everything in between. 

The other value in them is the way they develop over time into more and more spectacular plants, so that a garden of rhododendrons is an investment in a garden of unsurpassed glory. The third may be less obvious, but it is no less interesting. The plants we grow in gardens are not, mostly wild plants. They are the products of a period of intense breeding in the first half of the 20th century, largely in England, but in Europe and America too. The associations can be remarkable.

Take the Blue Diamond Rhododendron. Not only is this one of the closest varieties to true-blue, with wonderful blooms that are technically mauve-purple, but sure look blue to most gardeners. This is also a different-looking plant, not only famous for its ‘blue’ flowers, but also, remarkably, linked with Florence Nightingale, the founder of modern nursing. It was bred and raised at her family home, some years after her death, when her sisters were living there – who would have thought of such an unusual connection between a garden plant and an heroic woman.

Growing the Blue Diamond Rhododendron

Size and Appearance

The Blue Diamond Rhododendron is a vertical to rounded, upright bush, growing about 2 feet tall and wide within a decade, and then continuing to grow more slowly indefinitely. It has a shrubby form with many slender branches, very different from the usual thick-branched rhododendrons. The leaves are not large and leathery either, but small, about an inch long, abundant, making for a bushy plant, and for those more botanically-minded, part of a special group of rhododendrons called ‘Lepidote’ because on the underside of the leaves you will find an abundance of flat scales, giving the foliage a very different look from the usual leathery and glossy leaves of many others. Impress your friends with your knowledge of your plants by pointing them out. Only a limited group of rhododendrons from China, central Asia and northern North America have them. The leaves are evergreen, firm but thin, and dark green in color.

This is a different plant in another way too. It is early blooming, often in full bloom by the second-half of April in mild areas. So it really gets the season off to a flying start. The flowers are large, 2 inches across, almost flat circles of 5 partially-fused petals forming an open face. The flowers are at the ends of every branch, in trusses of 5 blooms, creating a spectacular display of special purity, because the flowers lack the typical dots and blotches seen on many varieties. As for the color, well you decide. Is it blue? Is it purple? Much depends on temperature, light, soil, general plant health and time of day, but if you want a blue rhododendron, this is about as close as it gets. Whatever you choose to call it, it is very beautiful, and sure to please even more than you expected -what a glorious bush this is, and perhaps the very best of all the blue rhododendrons (there aren’t many).

Using the Blue Diamond Rhododendron In Your Garden

The unique coloring of the Blue Diamond Rhododendron makes it ideal for a showy specimen in your garden. Plant it among other Rhodos, grow it in a large pocket in a rock garden, plant it at the edges of woodlands, or on rocky slopes. The possibilities are endless, and so is the beauty.

Hardiness

Sadly out of reach of zone 5, the Blue Diamond Rhododendron is hardy in the warmer half of zone 6, and thrives in zones 7 and 8 – climates not unlike the home in western China of its parent species. It grows best in places with plenty of summer rain, and temperatures that are not too extreme.

Sun Exposure and Soil Conditions

Again the Blue Diamond Rhododendron is different, because this is a plant that thrives in full sun, or with some afternoon shade. Don’t plant it in the more typical spot in light shade, but give it plenty of sun, even in zone 8. The soil of course must be acidic, ideally around 5.5, but certainly not above 6.5. You could grow it in a pot filled with lime-free potting soil in zone 8, if you don’t have suitable soil in your garden. As well as acidic, the soil should be well-drained by almost always moist, and rich in organic matter, with plenty of lime-free compost added when planting, and used for mulch each year. Rotted leaves mixed with pine needles and some peat moss is a good choice for all this.

Maintenance and Pruning

Once you have the soil, light and watering right, this is an easy plant to grow. Ignored by deer and rabbits, and rarely suffering from any pests, it never needs – and should never be – pruned or trimmed, beyond removing any dead twigs. When young it benefits a lot from dead-heading. Once the last flowers have fallen, take hold of the finished truss and snap it off just above the first leaves. It’s easy once you get the idea. Use your hands, not pruners, which may also remove the new shoots, which you will see sprouting just above the older leaves. This encourages much more flowers the following year.

History and Origin of the Blue Diamond Rhododendron

Embley Park, in Hampshire, England was the family home of Florence Nightingale. She died in 1910 and the house passed to her two sisters, until it was turned into a school in the 1940s. The gardener there was J. J. Crosfield, and he created the plant called ‘Blue Diamond’, releasing it in 1935.

This is a complex hybrid plant, basically a cross between a Chinese species called Rhododendron augustinii and other Chinese species from Yunnan and Sichuan in western China. R. augustinii is named after the famous French naturalist and priest who worked in China in the 19th century, August Henry, but it wasn’t introduced into England until 1926. Two earlier introductions from Western China were Rhododendron fastigiatum, brought out of China by the English collector George Forrest in 1906 and R. intricatum, arrived in the West in 1907 from the famous American collector Ernest Wilson. Those last two, crossed together, created a group of plants called the Intrifast Group, and done several times in the hunt for the blue rhododendron. Crosfield hybridized an Intrifast plant he had with the newer R. augustinii to create his blue rhododendron.

Buying the Blue Diamond Rhododendron at the Tree Center

So if, like those early plant explorers in China, you are on the hunt for a blue rhododendron, then take off your boots, the hunt is over. The Blue Diamond Rhododendron is as blue and sparkling as they come, and we have found a wonderful source of this plant to offer you – top-quality plants of a top-quality variety. Order now, chances like this just don’t come around very often.