JARS v60n1 - Companion Plants: Rhodos and Gentians

Companion Plants: Rhodos and Gentians
Bernie Guyader
Courtenay, British Columbia

Now do we say "Rhodos and Gentians" or "Gentians and Rhodos"? I suppose that if you are a rhodophile the first order would be yours. No matter the order, they make a great combination. (Companion plants anyone?) Our garden is in large part a rock garden with many alpine plants. Whenever I read or attend talks on companion plants, I am amazed that there is never any mention of gentians. I suppose, I may be prejudiced due to the fact that gentians are my favorite plants. I feel that the best companion plants have the same horticultural requirements as rhododendrons and bloom at different times, or complement the rhodos when they are in bloom. I think, possibly, the reason more people do not grow gentians is because they have been told they are difficult. I have found that if you give them the proper conditions most of them will grow and blossom happily for many years.
I suppose if we mention alpines, we should first consider the rhodos that are native to the Alps of Europe, which are Rhododendron ferrugineum found on siliceous subsoil and R. hirsutum found on calcareous subsoil. We also have Rhodothamnus chamaecistis , which was previously known as Rhododendron chamaecistus . These are all perfectly happy on a well-drained rockery, in full sun with a mulch of 5 to 8 cm (2-3 in.) of shale or rock chips. I should mention at this time I also grow R. calostrotum ssp. keleticum Radicans Group on the rockery, but on the north side in a more shaded area. With the alpine rhodos you can grow Gentiana in the acaulis group, such as G. alpina , G. kochiana , G. dinarica and G. clusii . Gentiana clusii in my garden is more lavender than the usual deep blue of the others. It may not be to everyone's liking. These evergreen gentians with their large showy trumpets, most of which are approximately 8 cm (3 in.) long in a deep rich blue, bloom at the same time as the rhodos. The plant height is about 7 cm (2.5 in.) with the flower rising up to 15 cm (6 in.) above the foliage. They simply require a well-drained, gritty soil in full sun. I top dress them with a handful of screened compost in early winter. The compost is worked in by the winter rains or even better by the melting snow. I think most people lose these plants or have them do poorly because they treat them too kindly, giving them too much moisture and fertilizer. Blooming during the summer, given the same conditions, are Gentiana septemfida , G. lagodechiana and many other gentians from the Alps and the Caucasus. They are deciduous and grow to a height of 25-30 cm (10-12 in.). I also have a summer gentian that I grew from seed I received from a seed exchange. It is supposed to be Gentiana paradoxa . It is a great plant with some of the features of G. paradoxa , probably a hybrid, definitely not G. paradoxa . I think it is the best summer flowering gentian I have grown.

North facing raised bed in 
the garden of Bernie Guyader.
North facing raised bed in the garden of Bernie Guyader.
Photo by Bernie Guyader

The following plants in our garden grow in a raised bed about 20 feet by 10 feet, on the north side of our house. The gentians, which grow here where it is a little more shaded and stays moister, are the August blooming G. asclepiadea , or willow gentian. It comes in many shades of blue and there is a white form, which is a little taller. They have upright arching stems to about 50 cm (20 in.). They happily hybridize and sow themselves through the garden. The Asian gentians such as G. sino-ornata , G. ternifolia , and their many hybrids, bloom in September and October. They are mat forming with dark green foliage with large trumpets from the darkest blue to white. These are the easiest to propagate as they root where the stems touch the moist soil. Gentiana paradoxa , from the Caucasus, is also fall flowering. It has a long blooming period sometimes extending from August to October. It is more upright but does tend to trail. It is very attractive - pale blue with dark stripes. They blend in well with Cyclamen hederifolium , both pink and white forms, which bloom at this time. When the cyclamen blossoms finish, the colorful foliage in dark green and silver carry on the show.

Gentiana paradoxa hybrid?
Gentiana paradoxa hybrid?
Photo by Bernie Guyader
Gentiana acaulis
Gentiana acaulis
Photo by Bernie Guyader
Gentiana sino-ornata 
Gentiana sino-ornata 'Kingfisher'
Photo by Bernie Guyader

These companions are happily mingling with the rhodos. I am drawn to the dwarf and low growing rhodos, because they fit in so well with the over-all scale and scheme of things in our garden. I much prefer the species but I have many hybrids as well. The species are Rhododendron impeditum , R. calostrotum ssp. keleticum , R. williamsianum , R. cephalanthum and R. pseudochrysanthum . I have two R. campylogynum hybrids, at least I think they are hybrids. I got them from Tom Bowhan several years ago. One he named 'Ester Berry'*, which is very attractive, and another which has dark shiny green foliage and a dark plum colored bell blossom is one of my favorites. With these I have some of the "birds" from Peter Cox. Centered between two bright blue hepaticas is R. 'Ptarmigan'. The hepaticas blossoms slightly before 'Ptarmigan', but they are still in full bloom when the pretty white bells of the rhodo open. 'Kim', another R. campylogynum hybrid, is another favorite, even though Cox calls it muddy. Rhododendron williamsianum with its pink bells is between 'Ptarmigan' and 'Egret' - great contrast.
Also in this bed we have Trillium hibbersonii (also, T. ovatum f. hibbersonii ), a dwarf species native to Vancouver Island, about 5 cm (2 in.) tall with pink blossoms on 3-inch stems, and Cyclamen coum , which blossoms in the spring.
One other gentian which I have in the garden is Gentiana calycosa . It grows to approximately 30 cm, has a large tubular, light blue blossom. This is a North American native, which is found from British Columbia to California growing in meadows.
In conclusion, think gentians. There are over 400 species so there's quite a choice. Many different colors and sizes ranging from mat forming to the 100 cm (36 in.) G. lutea , which is yellow, and the root is used to flavor schnapps. I have mentioned the ones that are most likely available and the easiest to grow, and they are natural companions to rhodos. You might have to search for them at specialty nurseries, one of which is Mt. Tahoma Nursery, but they are worth every effort. For more information read Gentians by Fritz Kohlein of The Genus Gentiana by Josef J. Halda.

* Name is not registered.

Bernie Guyader is a member of the North Island Chapter.