Rhododendron arboreum

R. arboreum is possibly the most widespread rhododendron in the world.  The plants grow in the wild in southeast Asia occupying a wide arc on the southern slopes of the Himalaya Mountains, from Kashmir through Nepal, Sikkim, Bhutan, and Manipur, a distance of about 1,500 miles.  In its native habitat some arboretum forms can grow up to 60 feet tall, but in cultivation, it rarely grows over 40 feet.  Most experts say it will grow to be about 6 ft. tall in 10 years. So don't let its mature height keep you from planting one in your garden.

The leaves of R. arboreum are large; 4 to 8 in. long and up to 2 in. or more wide. They are thick and leathery. Arboreum leaves are glossy, deep green on top, with the underside covered with a thin plastered or woolly indumentum that varies in color between different subspecies. The color of the flowers varies considerably, from white to shades of pink or red. Some of the white and pink forms sometimes will have deeper colored spots which add to their interest and beauty. All have nectar pouches at the base of the flower. Flowers are bell-shaped and are held in trusses of 15 to 20 flowers. The blood-red forms are generally considered to be the most tender.

Since the British Empire previously occupied much of the area where R. arboreum grows, and much of the early rhododendron hybridizing occurred in the British Isles, the species has been often used as a hybrid plant parent. Arboreum seed was first sent back to Britain from Nepal almost 200 years ago. Some examples of hybrids where R. arboreum has been used as a parent include:

R. 'Bibiani', ('Moser's Maroon' x R. arboreum ssp. arboreum)

R. 'Cornubia', (R. arboreum ssp. arboreum, red form x Shilsonii Group)

R. 'Doncaster', (R. arboreum ssp. arboreum x unknown)

R. 'Loders White', (R. arboreum ssp. cinnamomeum var. album x R. griffithianum)

R. Nobleanum Group, (R. caucasicum x R. arboreum ssp. arboreum)

Rhododendron leucaspis

Last year while attending a local rock and alpine garden show, I saw Rhododendron leucaspis in bloom for the first time and it immediately went to the top of my wish list. I looked around for a plant locally without success and had to put it on the back burner. So time passes and a few months later, I'm on my way to the ARS western regional fall conference in Newport Oregon and on the way there I decided I wasn't going to buy any plants, (Yeah, right!) as I was going to be on the road for a few days before heading home, and didn't want to have to fuss with looking after plants and deal with the border crossing. But, wouldn't you know it, the first plant I spotted on the Rhododendron Species Foundation's sales table was R. leucaspis, and I just had to have it - so much for resolutions about not buying anymore plants!

The plant I saw at the rock and alpine show is wintered under cover. The grower, a fellow "rhodoholic", thinks it might be a bit tender here in Victoria and I didn't want to take any chances with my new plant, so I over-wintered it in my sunroom - probably a good idea as this past winter was longer and colder than we've had in awhile. I've since learned from others that they're able to grow R. leucaspis outside reliably, so it is probably totally hardy in zone 7. My new plant was loaded with flower buds and blooming started in mid-February. It finished blooming at the end of March and in addition to lovely white flowers, to my delight, the flowers had a light fragrance, most noticeable when the temperature rose.

R. leucaspis is a small plant with clear white flowers. The stamens are very dark and stand out against the white petals. The petals are slightly reflexed, giving the flowers a nice, open appearance. Flowers are about 2 inches across and are held two or three to a truss. The plant itself has "smallish", dark green, slightly hairy leaves which provide a wonderful background to the white flowers. The plant height is about 2 feet in ten years. Since it is a small plant, I intend to keep it in a container, at least for now.

There are lots of great reasons to attend the ARS conferences: nice people, good talks, wonderful gardens to visit and the plant sales. I have no regrets that I didn't stick to my resolution of not buying another plant! I've made the same resolution about not buying anything at the 2017 Eureka ARS Convention, but I wonder what treasures I'll find and just have to have?

Legal-tender Rhododendron Coin

In September 2012, the Royal Canadian Mint released the $20 Rhododendron Blossoms Pure Silver Proof as the third coin in the Crystal Dewdrops Series and Wildflower Series and the eighth release in the Swarovski Crystal Flora Program. The image is that of the Pacific rhododendron (Rhododendron macrophyllum) from the North American Pacific Coast, which is enjoyed in gardens across much of North America. The Water Lily Pure Silver Proof (2010) was the first in the Crystal Dewdrops Series and the third release in the Swarovski Crystal Flora Program, while the Wild Rose Blossoms Pure Silver Proof was the second in the Crystal Dewdrops Series and the fifth release in the Swarovski Crystal Flora Program.

Rhododendron coin

The coin's special features are an artistic rendering of two pink-coloured Pacific rhododendron flowers and a bud, three crystals nestled among the rhododendron's petals and leaves, a Finish Proof, a limited mintage (10,000), and a composition of fine silver (99.99% pure).

The coin comes enclosed in a maroon flock-lined clam-shell case, is protected by a black sleeve and has a serialized certificate to document its quality. The coin weighs 31.39 g (1.11 oz US) and has a diameter of 38 mm (1.5 in).

Rhododendron Winter Damage and Prevention

Frost causes considerable damage to leaves, stems, buds, and flowers of some rhododendrons. On damaged plants leaves will be distorted, curled, and may grow only on one side of the main vein. Part or all of a winter-damaged leaf will be brown-colored. If too unsightly, remove the damaged leaves.

Some rhododendrons protect themselves from winter dehydration by drooping and curling their leaves as temperatures decrease. Leaf movement occurs rapidly and it is reversible as temperature warms.

Frost also will cause the bark of affected stems to split longitudinally near ground level...even peeling away. This typically happens in early fall or late spring when the plant is not fully dormant. Often these symptoms are overlooked and damage only noticed at a later date. If noticed recently after the injury and before the bark has had time to dry out the area can be wrapped with galvanized wire or a non-sticky wrapping. Check the wrapping monthly and remove the wire when the repair is successful.

Cold weather may cause branches to appear to be dead. Wait until late spring then scratch the bark on dead-looking branches. If there is green wood underneath, the branch is still alive, leave it in place. If it's brown underneath, the branch is dead and can be pruned off.

Cold weather can kill flower buds. Dead buds are brown-colored and easily break off. Often rhododendron buds are less hardy than other parts of the plant. Choose varieties that are bud cold-hardy for your area.

Because rhododendrons roots are very shallow, it's important to use a thick layer of mulch to provide protection from the cold. It'll also slow water evaporation from the ground, helping plants to stay hydrated. On warm days water your plants so they have a chance to survive cold periods.

A windbreak made from burlap, lattice or a snow fence can help prevent damage from winter's drying winds.

Finnerty Gardens

Finnerty Gardens has one of Canada's best collections of rhododendrons. Located on the University of Victoria grounds the spectacular garden contains over 4,000 different trees and shrubs with more than 1,500 rhododendron and azalea plants, including 200 collected rhododendron species, and a wide range of companion plants artistically displayed on a 6.5 acre site at the southwest corner of campus.

The Gardens were developed in 1974 when the estate of Mrs. Jeanne Buchanan Simpson of Cowichan Lake was left to the University. She and her husband George, beginning in the 1920's, built up a notable collection of rhododendron species at their Lake Cowichan home. Many plants were grown from seed obtained directly or indirectly from famous plant explorers of the day. Theirs was the largest rhododendron collection in British Columbia. The University decided to move many of the rhododendrons to their campus where they would form the nucleus of a new garden that was created on nearly three acres of land at the south end of the campus.

After the death of her husband, Mrs. Simpson had been unable to maintain the garden properly. The rhododendrons had to struggle for survival without the benefit of summer watering and in competition with the invading "jungle". The Simpson plants were up to 50 years old and presented a challenge to the transplanters. You will recognize these sometimes distorted giants in the Garden today. Most of them are R. decorum or R. fortunei.

The gardens have been carefully planned and developed to provide a rich and changing array of colour, scent, form and texture all year round. In April and May, you will see the rhododendrons at their best. For a plant identification guide and map of the gardens, download a self-guided walking tour pamphlet. For more information about Finnerty Gardens visit their website.

Little Sweetheart Rhododendrons

Much as I love the big, bold, beautiful Rhododendrons, I have a small garden so I grow mostly small species and hybrids. Some of my all-time favourite species are R. pruniflorum, R. sargentianum and R. campylogynum. As container specimens, all have been reliably hardy for me in the Victoria area for many years and all are easy growers.

I started with small well-rooted cuttings, originally grown in 4 inch pots and over time, have moved the plants up to larger containers. The current pot size capacities are, more or less, 3 gallons. My potting mix is coarse peat, perlite, some coarse sand and if I've got it, a bit of garden compost. I do want a well-drained mix, so there's no more than about 40% peat in the mix. I know many people are cautious about fertilizing some Rhododendron species, but I give my container-grown plants a light application of slow release fertilizer in the early spring. Since they're in pots, there's considerable leaching so I think some fertilizer is appropriate. Some of our local growers just top dress their potted rhododendrons with Seasoil (a form of composted fish fertilizer) once each spring, and this works well for them.

I keep my plants in a location where they get full sun in the morning, but by about 1 pm, they are in the shade. Good light is needed to set flower buds, so if you have some of these smaller species and they're not blooming for you, perhaps a bit more light is in order. I water freely on an as needed basis, and I make sure the drainage holes remain open since there can be problems with containers if they're sitting directly on the soil surface where the holes may gradually get plugged. I like to have some sort of top-dressing on the soil surface to prevent too much surface compaction from all the watering I do. A good layer of orchid bark makes an attractive mulch, but sometimes I use turkey grit, or small-sized pea gravel. However, if you like to show your plants, most show judges prefer to see bark mulch used as a top-dressing as they often think write comments that they think gravel isn't aesthetically suitable for rhododendrons. Personally, I like the look of gravel or grit and it lasts longer than orchid bark.

Rhododendron pruniflorum has thimble-sized bell-shaped flowers of a dusty plum colour. It's absolutely adorable in bloom. The leaves are small, a nice dark green on top and white underneath. My 6-year old plant is about 18 inches tall and 18 inches wide. Many of us grow R. campylogynum and there are several forms available - all of them are very nice. But, my favourite (and I have a couple of forms) is R. campylogynum Leucanthum. Again, the thimble-sized flowers are bell-shaped, but in this case they are white in colour. Rhododendron sargentianum has small, ball-like trusses of white to ivory coloured tubular flowers. The tiny leaves are a nice shiny green and if crushed, give off a scent. The scent isn't unpleasant, but it makes me sneeze. I have a plant of the straight species, but recently acquired a plant of the selected variety 'Liz Ann' which is stunning in bloom as it just covers itself in pure white flowers. These plants are also about 18 x 18 inches and range in age from 3 to 7 years old.

A very similar looking plant to R. sargentianum is R. primuliflorum, but, with primuliflorum, the tubular flowers range in colour from white to soft pink and even yellow. It also has scented foliage. I've just recently been given a pink flowering form of R. primuliflorum and I'm looking forward to seeing it in bloom next spring.

One of the advantages of growing plants in pots is that I can move them onto the porch when the plants are in bloom, so while the plants and their flowers are small, I can get up close and personal with them easily. You know the adage, great things come in small packages, so if you only have a small garden, consider growing some of these lovely little sweethearts.

 
15505