Companion Plants for Rhododendrons
Victoria, British Columbia, Canada
Reprinted from the Victoria Rhododendron Society newsletter, September 2000
Part I - Perennials
Companion plants can come in all sizes and varieties - herbaceous perennials, evergreen shrubs, bulbs or even vines. Any plant that will enhance the foliage and perhaps blooms of a rhododendron can be considered a companion plant. Rhododendrons are wonderful backdrops to the smaller spring carpeters such as Anemone nemerosa ranging in colour from pristine white, pink through to the lovely deep blue of Anemone 'Robinsoniana'. For a bright yellow statement try the Anemone ranunculoides equally at home under a rhododendron. Keep in mind that these little plants will go dormant in July and then reappear next spring. For all season interest, try the bright chartreuse bracts of Chrysoplenium davidianum - a creeping little plant ideally suited to a woodland garden.
For late winter foliage Cyclamen hederifolium and C. coum are perfect companions for smaller rhododendrons. They have marbled and beautifully patterned leaves. The bright cerise pink coum blossoms in late winter, and the pink or white blossoms of hederifolium in late summer give lots of colour. Also, for winter interest, the hellebores are good companions for rhododendrons. Helleborus niger (the Christmas rose) is a perfect complement for rhodos. Give this plant some overstorey protection from rain so the beautiful white blossoms will not be marred. Helleborus orientalis gives excellent foliage when not in bloom but provides a wonderful range of colour and patterns when blooming from as early as January to April. Be sure to site the deep purple hellebores where they can catch the low winter and early spring rays of sunlight and they will be even more appreciated.
Ferns are great additions to the woodland border and come in a vast range of sizes and varieties. One of the smallest and most delicate in pattern is the evergreen Adiantum venustum. This fern is often called the Himalayan maidenhair fern, an excellent partner for any rhododendron. Another evergreen fern with bright green new foliage and great texture is the bird's nest fern, Asplenium scolopendrium - seek out the form called 'Crispum' which will give even more interest with its rippled fronds. Foliage daintiness can also be found in the dicentras - two recommended for not only great texture but glaucous blue leaves are 'Boothman's' and 'Langtrees'.
For contrast whether it be colour or variegation, there is a vast assortment of perennials that provide lots of interest throughout the summer. Pulmonaria or lungworts are notable for their pewter and silver markings on their leaves. Two favourites of mine are Pulmonaria 'Spilled Milk' and 'Excalibur', which has almost entirely pewtered leaves. Another variegated beauty is Brunnera macrophylla 'Variegata', which has clearly defined white and green foliage. This plant really relishes deep shade and lots of moisture. For purple foliage the Euphorbia dulcis 'Chameleon' is very adaptable to shade and full sun and looks especially good beside some golden grass or golden foliaged hosta such as Hosta 'Abiqua Recluse'. Another golden large hosta is 'Sum & Substance' - outstanding for its puckered foliage and sun resistance. For a variegated hosta try the Hosta 'Patriot', relatively tolerant of slugs. It also keeps its clear white and green markings all through the summer.
For structural contrast there is the tall Polygonatum commutatum or Solomon's seal - a good plant for its slug resistance and easy care. For lushness and large leaved effect the Diphylleia cymosa gives impressive leaves, red stems and purple mahonia-like berries. Another recent Chinese introduction is the Podophyllum pleianthum - a relative of our East Coast mayapple, it provides glossy toothed umbrella-like leaves that never fail to draw attention in the garden.
If one wishes for unusual stature or impressive foliage, I would recommend the Arisaema taiwanensis for its sinister mottled stems and flattened leaves each ending in a long drip tip. Another arisaema reminding one of a cobra is the Arisaema ringens with its hooded purple spathes and glossy trifoliate leaves.
Part 2 - Shrubs, Vines and Trees
The category of shrubs is vast, but there are some particularly good ones that complement rhododendrons - species peonies such as the yellow Ludlowi lutea and the deep burgundy Delavayi. Both accept shaded conditions readily. Neither needs staking and their fern-like foliage and large seed heads can add another dimension when interplanted with rhododendrons. A lesser known shrub needing little care is Neillia tibetica which has a pendant habit with rosy pink racemes. The genus Rubus provides some very good companion plants. Rubus lineatus has wonderfully pleated foliage and frosty white indumentum. Rubus henryi is a vine with trifoliate leaves reminiscent of bamboo. Both these rubuses are semievergreen requiring a sheltered situation.
For sheer glory in the summer garden the Sambucus nigra 'Guincho Purple' will give great pleasure. Its deep purple new foliage is handsomely topped with broad pink panicles of blossoms which are then followed by shiny clusters of black berries. The variegated form S. nigra 'Albovariegata' is equally impressive in deep shade with its creamy white markings - great for those dark green rhodo leaves.
The next exceptional group of companion plants has to be the hydrangeas. Relishing similar conditions needed for rhododendrons, they can provide the garden with extra interest when it is most often needed - late summer. The lacecaps come in a large range of colour from 'Blue Wave', a deep blue if soil is acidic enough, clear white as in 'Lanarth White' or deep pink with dark foliage - Hydrangea serrata 'Grayswood'. Hydrangea 'Ayesha' with its glossy leaves and dense pink blossoms is another distinctive plant that can look very good at this time of year. The hortensias or mopheaded hydrangeas also have some very good cultivars. Hydrangea 'Emile Mouilliere' is clear white but has bright purple-blue eyes in the center of each scalloped petalled blossom. For a treelike variety of hydrangea the Hydrangea aspera macrophylla is very impressive with its hairy apple-green leaves and its enormous mauvy-pink lacecaps in late summer. Remember to site these plants out of the wind.
For all year interest, the shiny deep green leaves of Azara microphylla would be perfect companions for rhododendrons. Provide a sheltered spot for this plant so you can enjoy its tiny bright yellow blossoms, vanilla-scented in early spring. The variegated form of this small tree is equally as impressive. Taking variegation to the ultimate is the almost devoid of chlorophyll Acer 'Ukigomo' (floating cloud) which really lights up a densely shaded spot. Be mindful of its constant need for shade and moisture. And lastly, for the patient, try the variegated forms of dogwoods: Cornus mas variegata, C. alternifolia argentea and the wedding cake tiered tree, C. controversa 'Variegata'.