That climbing plants like to climb may seem like a fairly obvious statement, but bear with me: it really isn’t.
You see, we like to grow climbing plants (plants that mount trees, treillises, walls and other tall objects), especially climbing houseplants, in hanging baskets, with their stems dangling downwards. They certainly look pretty enough grown that way… but they don’t much like it.
Many will start to produce smaller and smaller leaves the longer they dangle. That’s the case of most aroids, including philodendrons and pothos, as well as many Cissus. Sometimes they stop producing leaves entirely, producing only a lengthening green stem. Others just stop growing after they’ve dangled for a while or refuse to bloom on any stems that trail. That’s the case for morning glories (Ipomoea spp.), for example.
Of course, many climbing plants will fight tooth and nail against dangling. The afore-mentioned morning glories will quickly start to twine back up around their own stems in an effort to grow upwards again. If you won’t let them, untangling their stems so they trail further, they will stop growing and certainly won’t bloom.
This reaction is due to hormones called auxins present in their stem tips. They concentrate in the uppermost part of the stem and stimulate growth. When the plant hangs in what is essentially an upside down position, the auxins become diluted and growth decreases or ceases.
Finding a New Support
In the wild, when a hanging plant becomes disconnected from its support, it will often trail downward to the ground, producing increasingly smaller leaves, then its stem wanders off across the soil until it finds a new support it can climb.
At this stage, it will actually grow away from the light, an action called negative phototropism, normally a most unplantlike thing to do. But there is a method to this madness: deep shade can be caused a tree trunk or other upright object it might want to climb on. And it desperately wants to climb.
So off the stem heads towards the darkest thing around. Once it finds it, it starts growing upward again, takes up positive phototropism like any normal plant, and soon its leaves start become bigger again. Happiness at last!
When Climbing Plants Do Climb
If you switch techniques and allow your climbing plants to climb, perhaps up a trellis, a moss pole or a wall, rather than trail from a pot, many will do some striking things. Many aroids (philodendrons, pothos, monsteras, etc.) will begin to produce larger leaves — much larger leaves — when they climb. And much thicker stems too.
Did you know your good ol’ heartleaf philodendron (Philodendron hederaceum, syn. P. oxycardium, P. scandens and P. cordatum), whose leaves are often barely 2 inches (5 cm) wide when it trails, is capable of producing leaves 1 foot (30 cm) in diameter when it climbs?
And that pothos (Epipremnum aureum, syn. Scindapsus aureus) growing half neglected in the corner does the philodendron one better: at maturity (that is, when it grows upright and gets decent light [also a factor in leaf size]), not only do its leaves grow to enormous sizes, up to 40 inches by 18 inches (1 m by 45 cm), but they become deeply cut, like those of a monstera.
This increase in leaf size is also linked to sexual maturity: once they reach their full leaf size, these aroids will start to bloom and produce seeds. You thought philodendrons and pothos simply didn’t bloom? Try growing them up a tree in a tropical climate (most rooms aren’t tall enough to get them to flowering size) and they will bloom.
Other climbers keep producing small leaves as they climb, leaves that don’t change in size at first, often not for years. Then, when they’ve climbed high enough, they suddenly switch from this juvenile form to their mature form, with much larger leaves often of a very different shape and they too start to bloom and produce seeds. True ivies (Hedera spp.) do this, as does the creeping fig (Ficus pumila).
Some Climbers Don’t React
Not all climbers react badly to dangling. I’ve never seen a wax plant (Hoya spp.) that seemed to mind whether it was growing upwards, downwards or sideways, for example.
And then there is the case of creeping plants we use in hanging baskets, like wandering jew (Tradescantia sp.) and Swedish ivy (Plectranthus). Although we might mistake them for climbers, they aren’t really aren’t: in nature, they’re groundcovers, wandering sideways, rooting as they go and forming carpets on the ground. They grow and bloom perfectly when you let them hang and even if you force them to grow upwards by fixing them to a support, that won’t change their leaf size or habit.
The same is true of epiphytic plants (ones that grow on tree branches), like the lipstick plant (Aeschynanthus spp.) and the goldfish plant (Nematanthus spp.). They look great in hanging baskets because they naturally arch outwards and downwards and are perfectly happy to bloom this way. But they aren’t true climbers.
Most true climbers will react positively if you allow them to grow the way Mother Nature intended them to do: upwards.
Try it and see!