Have you noticed that there are a few horticultural ideas that are ubiquitous staples in books, blogs and catalogues, yet you barely ever see in gardens? These range from outdoor aubergine plants loaded with fruit on our blustery North Atlantic islands, to advice on getting poinsettias to reflower year after year instead of inevitably giving up the ghost before the Christmas decorations are down. In my experience at least, I feel I am more likely to see a unicorn than any of these in reality. However, sometimes – just sometimes – you meet an excellent gardener who gives you a simple tip that changes everything. So here is why I no longer count the notoriously finicky indoor maidenhair ferns (Adiantum sp) on my “unicorn plants” list.
A few years back, I was lucky enough to be invited to record a feature for Radio 4’s Gardeners’ Question Time at fellow panel member Anne Swithinbank’s house in Devon. Now, Anne has been one of my horticultural heroes since I was a child, so, for me, going to see her famous collection of houseplants was a bit like going to Poison Ivy’s supervillain lair. However, of all her indoor gardening wonders, I was truly spellbound to see her indoor adiantum. In a large bowl, its feathery locks cascaded down in perfect emerald green, giving me a flashback to seeing the same species in the wild in mossy jungle gorges. Just magical. But how did she do it?
What makes maidenhair ferns so tricky to grow as houseplants is that their ideal habitat just isn’t that easy to replicate in most our homes. Their common name in Latin America, Culantrillo de Pozo (literally, “well coriander”), gives you an indication of their perfect habitat: the stone walls of wells are often entirely clothed in their fresh green fronds. The perfect growth spot is a cool, shady and exceptionally humid area, with moisture-laden air and a root zone that is perpetually damp but never waterlogged. Sadly, our homes usually offer the exact opposite conditions, with centrally heated winter air holding less moisture than the Sahara. And they are sold in small pots of peat-based growing media that dry out incredibly quickly, so you need to check on them almost daily to ensure they don’t collapse from prevent drought stress, with their leaves crisping up almost before your eyes.
Anne’s ingenious tip was two-fold. First, she had a generous group of them in a large china bowl. The glazed vessel wasn’t subject to the wide swings in moisture than can happen in small, porous ones, and grouping loads of plants together created a bubble of localised humidity which helped seal a layer of protective moisture around their delicate leaves. Anne says that even she finds adiantums tricky when they are small, but they get easier as they become more established. A super easy way to speed up this process from day one is to plant up a group of three, or preferably five, store-bought plants, in as big a container as possible. The second tip: Anne has hers in an unheated sun room, and this lack of radiators will make for far higher air moisture. Not everyone has a sun room, but kitchens and bathrooms do have naturally higher humidity. I really couldn’t believe such a simple idea would turn one of the very hardest to grow houseplants into one of the easiest, so here’s to learning from your horticultural heroes.
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