Everything you need to know about climbing plants and how to choose them
Sun lovers, shade seekers, best bloomers and the ones you should probably avoid
At some point every year I'm inspired to make a big decision about my garden. Often in spring or fall. Possibly while sipping a glass of rosé after a sweaty, satisfying day in the dirt. This year, I decided that the back of my garage needs something to cover the dirty siding — something to climb on it and create a tapestry of green, dotted with colourful blooms. Having never grown climbers, I decided to reach out to a couple of experts to ask them how to choose the right one for the job.
Jon Peter is the curator and manager of plant records at the Royal Botanical Gardens in Hamilton, Ontario and Stanley Luk is a Senior Landscape Designer at PFS Studio in Vancouver and an ISA Certified Arborist.
What's the difference between a vine and a climber?
Jon Peter: A vine is any plant featuring long stems with trailing, horizontal or climbing growth habits. Categorically, there is not much difference between a vine and a climber, although all vines don't necessarily climb and even some climbers can take on other forms (shrub form for example) if there is no support for them to climb on. Some vines/climbers are woody plants and some are herbaceous plants which die back to an overwintering crown each year. Herbaceous vines can be perennial (ie. bindweed, Convolvulus arvensis) or annual (ie. cucumber, Cucumis sativus).
Why do they climb?
JP: Vine species have evolved to spread and climb to gain a competitive advantage. Oftentimes the vines are seeking brighter light conditions by growing up a tree trunk to reach the higher sun exposure found in the canopies of trees. In some cases, the vining growth allows the species to colonize an area quickly without investing resources in producing supportive tissue (like a tree producing a trunk). In other species, the vine will want to have its roots in fertile soil with adequate moisture but also seeks to grow in full sun conditions, possibly on a nearby rock exposure. This allows the vine to root in the fertile soil and climb over to the preferred sun exposure. Climbing vines can also have a competitive advantage as they will grow out of reach of potential herbivores and by avoiding the shading from other ground layer plant species. Many vines will remain juvenile if growing horizontally along the ground and will become mature, flower, and produce fruits once they grow vertically and have reached the high sun exposure in the canopy.
What should we keep in mind when choosing climbers?
JP: There is a lot to keep in mind when choosing vines to plant. This could be the most difficult group of plants to work with and use properly in a garden or landscape. You will need to consider the method of climbing, environmental conditions (soil types, sun exposure, wind exposure, soil moisture), type of structural support, space available, and the intended maintenance regime. Of course, you will want to think aesthetically about colour, texture, flowering times, seasonality, screening, and how vines can soften hardscapes. You should also consider environmental factors — supporting wildlife and insects, erosion control and the species potential for invasiveness.
The methods of climbing are important to consider since some climbing methods will require supports (trellis, pergola) to twine around, objects (wire, guides) to wrap around, rock or bricks (or other structural materials) to cling to. Since some vines can grow large and become heavy over time, it is important to consider how much weight your supporting structures can withstand. I have seen hardy kiwi vine (Actinidia polygama) twirl itself around a wooden shade structure and became so mature and overpowering that it broke boards and lifted the structure out of the ground!
Charles Darwin placed vines into five classes based on the climbing method they employ.
Twining plants (aka bine) – twist stems tightly around supports. Ex. Bittersweet (Celastrus scandens)
Leaf climbers – grow leaves, leaflets, and petioles which curl and twist around one another or objects to climb supports ex. Clematis spp.
Tendrils – use specialized stems, leaves or petioles which are highly sensitive to touch and coil, curl, adhere, and twine around supports. Ex. Cucumber (Cucumis sativus), garden peas (Pisum sativum) and Virginia creeper (Parthenocissus spp.)
Root climbers – use adventitious roots along stems to cling to bark/supports/walls. Ex. Ivy (Hedera helix) and poison ivy (Toxicodendron radicans)
Hook climbers – use thorns or hooks to aid in upward support. Ex. climbing rose, Rosa spp.
What are some notable Canadian native climbers?
Stanley Luk: There are a few vines native to Canada that support wildlife and offer ornamental value; Virginia Creeper (Parthenocissus quinquefolia), American bittersweet (Celastris scandens) and Virgin's Bower (Clematis virginiana). There are many more climbing species that are cultivated as ornamentals from south of the border including Trumpet Vine (Campsis radicans) with large, trumpet-shaped flowers that blooms in late summer and attracts hummingbirds. However, this vine is rampant and spreads by underground runners so it is considered by many to be an invasive species. Major Wheeler Honeysuckle (Lonicera) provides masses of bright red tubular flowers almost all summer and is also a favourite of hummingbirds. Amethyst Falls Wisteria (Wisteria frutescens) is a beautiful bloomer, less aggressive and more hardy than Asian natives, Sinensis and Floribunda.
JP: Many of Canada's cultivated vines are non-native and in some cases like ivy (Hedera) and periwinkle (Vinca) can be destructive to the environment and become a nuisance in the garden setting. Whenever possible, it makes the most sense to plant vine species native to your local area. Not only will they adapt better to the growing conditions, they will likely require less maintenance while at the same time providing benefit to the native ecosystem. Some notable native vines are American groundnut (Apios americana) — a vine with beautiful fragrant flowers and edible, protein packed tubers (roots), American bittersweet (Celastrus scandens) — a dioecious (separate male and female plants) vining species known for its beautiful orange fruits providing fall and winter interest, Virginia creeper (Parthenocissus quinquefolia) — a hardy Ontario native with amazing fall colours and showy fruits which are attractive to birds.
Which species is the best bloomer?
SL: For fragrance, nostalgia and cut flowers, I would never be without sweet pea (Lathyrus odoratus). Sweet pea is an annual vine that comes in a wide array of colours including white, pink, red, mauve, lavender blue and darker blue/purple shades. Pioneering breeding work by Dr. Keith Hammett in New Zealand has expanded the colour range to include smokey orange, true turquoise blue, almost black as well as bicolor combinations never seen before. Sweet pea thrive best in cool temperatures, as hot temperatures trigger the plant to cease flowering and set seeds. In areas with hot summers like Southern Ontario, it is best to start them in February or March indoors and plant out seedlings in early spring, after the threat of frost, to get a head start. I currently live in Vancouver and the cool summer temperatures here allow me to extend the blooming period by starting a second crop of seeds in late spring for planting out in early June so that they bloom in late summer to fall after the first early spring planted crop is done flowering. The Exhibition Spencer varieties, with large blowsy flowers, can grow to the top of an 8' trellis in a few months and dwarf forms are available that are the perfect size for tumbling out of a window box. Since sweet peas are annuals, if you don't like the colour you get this year, you can try a different variety next year. A word of warning though, sweet peas are poisonous — especially the seeds, so don't mistake them for edible peas. Finally, remember to deadhead (remove the faded flowers and bloom stems) so that all of the plant's energy is focused on flowering instead of seed production.
JP: It depends on your preference. Some might prefer the intricate flowers of the Ontario and Quebec native groundnut (Apios americana), while others in western Canada might prefer the delicate blue flowers of the native western blue virginsbower (Clematis occidentalis var. grosserata) or the profuse flowers of the late season flowering Virginia clematis (Clematis virginiana), which is native in central Canada. If you're more of a classical gardener, you might enjoy the large, showy flowers of cultivated varieties of Clematis or the classic, fragrant, and pendulous racemes of wisteria flowers.
What would you suggest for full sun?
SL: Though it's difficult to suggest something that will grow everywhere in Canada, clematis hybrids are likely your best bet. These are hybrids involving various wild Asian, European and American species. Some can take a bit of shade but full sun maximizes flower production. There are species that bloom in spring, summer, fall — and if you live in Zone 8, on the sunny coast of British Columbia or have access to a cold greenhouse, even winter bloomers too. For sheer simplicity and hardiness throughout much of Canada, I would recommend 'Polish Spirit'. This is a Zone 4 clematis hybrid, has dark purple blooms and a delicate looking vine, but boasts a hardy constitution. It blooms over a long period starting in June and if deadheaded and lightly pruned after flowering, will bloom into September. While this plant needs to be pruned to a height of 4" from the ground in early spring, it will climb to the top of a 10' tall trellis by bloom time. Give it a sunny spot, plant some low growing perennials at the base to keep the roots cool, water and feed it well and it will give you lots of colour with minimal care.
What would you suggest for shade?
SL: I have had good luck with climbing hydrangea (Hydrangea petiolaris). A native of Japan, it's a woody climber that is hardy to Zone 5. This species can vine its way up a chain link fence, ascend a north facing brick wall, or even a dead tree trunk in a shady location without any assistance. It will take a year or two to establish a robust root system before it starts to climb following planting but you can expedite this process by buying as big a plant as you can afford and watering it deeply so that it never dries out. Once the vine is established, it will produce masses of white lacy flower heads that turn green and then brown as they age. The leaves turn a nice buttery yellow in the fall and once they fall, the buff flaky bark of the stout branches is exposed. In snowy areas, the twigs and dead flower heads catch the snow and create interesting effects in the winter garden.
How can we encourage climbers to grow and spread?
SL: Each species has specific needs. All vines need a good head start, so dig a planting hole two times the size of its root ball (larger if you can) and mix a 2" thick layer of well-rotted manure or compost into the hole. In general, good plant cultivation in well-amended soil with sufficient light and water will help vines climb and spread. However, too much feeding may encourage growth of foliage at the expense of flowers, this is especially true for rampant growers like Wisteria or Morning Glories that flower best in poor soil.
JP: Similar to most trees, shrubs, and perennials, when vines are planted in the landscape they will go through a period of transplant shock. The first year they sleep, the second year they creep and the third year they leap. After planting, it is important to irrigate your new plants as necessary. For most vines, additional nutrition (fertilizer) should not be necessary if the proper vine is chosen for the location. Make sure that you allow the vine good access to the structure which it will grow on. This means you may need some temporary braces in order for it to reach the final destination. Consider strategic pruning in the early years to keep stems going in the direction you prefer. If you are growing clematis, keep track of which types you grow as this will determine the best methods of pruning that is required (pruning clematis can be broken down into three groups, each with a different method of pruning).
Any invasive species to be aware of?
JP: Too many to count. Some of the worst, most destructive invasive plant species are vines. The combination of a rapid growth rate, excessive seed production, ability to root along their stems, capacity to strangle other plants, and overall the competitive nature of vines has allowed many species to become problematic. The potential for invasiveness depends on your location but in many parts of Canada, some of these species are already established invasives and some species are ones which we should be wary of planting due to the potential to invade as demonstrated in other regions of the world. It is important to recognize the invasive potential and to eradicate the problems early before these species get too far out of control. Even our native poison-ivy (Toxicodendron radicans) can be considered invasive given the risk it poses to human health.
Vine species which we have historically grown in our gardens and have become (potential) invasive issues:
- English ivy (Hedera helix)
- Oriental bittersweet (Celastrus orbiculatus)
- Porcelain berry (Ampelopsis glandulosa)
- Japanese & Chinese wisteria (Wisteria floribunda & W. sinensis)
- Five-leaf akebia or chocolate vine (Akebia quinata)
- Japanese honeysuckle (Lonicera japonica)
- Wintercreeper (Euonymus fortunei)
- Sweet autumn clematis (Clematis terniflora)
- Periwinkle (Vinca major & V. minor)
- Multiflora rose (Rosa multiflora)
- Trumpet vine (Campsis radicans)
- Grapevine (Vitis spp.)
Herbaceous perennial species which can be problematic to agriculture, landscapes and ecosystems:
- Bindweed (Convolvulus arvense)
- Bird vetch (Vicia cracca)
- Nightshade (Solanum dulcamara)
- Dog-strangling vine or swallowwort (Vincetoxicum spp.)
- Japanese hop (Humulus japonicus)
Some species which are threatening Canada with their destructive invasive tendencies:
- Mile-a-minute vine (Persicaria perfoliata)
- Kudzu (Pueraria montana)
- Chinese yam (Dioscorea oppositifolia)
Are there some climbers we should never plant?
SL: Unless you have the time, knowledge, or a fearless horticulturist friend who loves pruning, do not plant a Wisteria vine. If left alone, Wisteria can become a rampant tree-swallowing mass of foliage that rarely blooms. In order to bring out the best in a Wisteria, they require formative training when the vine is young and rigorous pruning once it is mature. The most important technique in getting Wisteria to bloom is to reduce the current year's growth to the lowest 5-7 buds in late summer. This may be a daunting task for a novice gardener to perform on an 8 foot tall step ladder!
JP: Gardeners definitely plant way too much periwinkle (Vinca major & V. minor) and English ivy (Hedera helix).
Are there tips for restricting them to a certain space or shape?
JP: Restricting vines to a certain space or shape is possible but it can be time consuming. During the growing season, some vines can put on multiple feet of growth in a short time, so being vigilant and consistent in your training regime is important. It is easier to properly train a vine while it is young and pliable and within reach. It can be very difficult to untangle mature specimens and then begin to train it to the shape you want. Look to remove stems heading in the wrong directions, guide stems in the direction you want them to grow, and don't hesitate to make some drastic but strategic pruning cuts. Also consider your annual pruning routine as some types of vines like wisteria and clematis can be particular to pruning methods in order to flower properly. Use wire, ties, or clips to hold stems to the structure or train them in the preferred directions. If your vine has already become too overgrown, for most vines, I would not think twice about completely rejuvenating the plant by cutting all the stems down to soil level and starting again.
What should I do if one section of my plant looks to be dying or troubled?
JP: If portions of your vine don't look as good as others, it could be due to many factors. Assess the symptoms that you are seeing, do some research, and make decisions about whether something can be done to correct the issue. Scratch the surface of the dying stems to see if they are green inside. Because vines generally grow quite vigorously, I wouldn't hesitate to remove troubled or dying portions of your vine. This will hopefully encourage new growth that will fill the void quickly.
What's your favourite climber and why?
SL: It's hard to pick one, but my favourite climbing plant for full sun at this time is sweet pea (Lathyrus odoratus). I love their delicate colours, ease of culture and unmistakable scent, which evokes memories of my mother's garden. Come to think of it, I think sweet peas were the gateway plant that got me hooked on gardening! If you have a shady spot or a north facing wall, my preference is the Japanese hydrangea vine (Schizophragma hydrangeoides). This species is very similar to the climbing hydrangea however, their showy sterile florets around the flower clusters have only one large sepal as opposed to four. This species is hardy to Zone 6 and sometimes down to Zone 5 in a protected spot. The dark blue green leaves with a silvery cast and masses of white flowers produced in midsummer merit close observation. Ask me again in a few weeks and the answer may be different; there are so many climbing plant species with different uses, it is hard to pick a favourite.
JP: It can depend on the day as to which vine I appreciate the most. One day it could be the Dutchman's pipe (Aristolochia tomentosa), an easy-to-grow twining species with unique flowers and a larval host plant for the pipevine swallowtail butterfly. The next day, it could be the silver tinted foliage and exquisite hydrangea-like flowers of the Japanese hydrangea vine (Schizophragma hydrangeoides). Most recently, I fell in love with a clematis with the cultivar name 'My Angel'. This clematis features masses of reddish-brown flower buds, opening to yellow on the inside, and followed by masses of silky seed heads. Ultimately, since I am a big fan of craft beer, I would have to say that hops (Humulus lupulus) is my favourite vine. Not only do they produce a delicious ingredient in the beer I consume, hops are amazing in that they grow quickly and look attractive when trained to grow vertically in the hopyard.