The Greenhouse Effect

Gardener extraordinaire HELEN DILLON believes greenhouses are as much for people as for plants …


I don’t think it matters how rickety or naff your greenhouse is – a bright, warm, frost-free area is a wonderful invitation to try out tender plants, start off seedlings and root cuttings. People think that greenhouses were invented for plants, but I secretly believe that they are all about serenity, a blissful escape from reality and a peaceful place to think – however much harassment stalks outside. An early morning trip down to the greenhouse, a quick watering, a sniff of fresh air and time to admire the favourite plant of the day – and calm descends.

The first greenhouse we built in Sandford Road, Ranelagh, circa 1974, was of soft wood, painted white, with plate glass for the doors and sides. Having once fallen through a glass door, I have the greatest respect for glass (I looked so wrecked afterwards, with 25 stitches on my face, that a man on a London bus remarked that I’d probably been just a pretty face before). By 1990 that greenhouse collapsed so we rebuilt it in hardwood, using the same glass. When we left that garden, in 2015, it was still in perfect condition.

One of Dillon’s new greenhouses in her garden in Monkstown, Co Dublin.

Getting a greenhouse built (as opposed to buying it made up) invariably involves arguments with the builder. Patience is required to politely explain that greenhouses heat up very fast in summer and, if you are out all day, masses of ventilation is essential. Make sure that the security of your house is not connected to the greenhouse in any way – you don’t want to shut it all up on a boiling summer day. As for heating, for many years we used old-fashioned electric metal radiators, which were very satisfactory. Now we use the easily available warm-air-blowing heaters – however, if I was a plant, I’d prefer not to be blown at all winter.

Notable plants I grew in these first greenhouses included a specimen of Lapageria rosea, the national flower of Chile, long considered the most beautiful climber in the world, with voluptuous, rose pink bells. I’m going to try it again in a greenhouse in the new Monkstown garden. It likes lime-free soil in part shade. I’ve always loved pelargoniums, which I first grew in the greenhouse when growing up in Scotland. I still grow the desirable dazzling scarlet Pelargonium ‘Ardens’. Cuttings are easily rooted, provided you take short cuttings, and bury them (leaves and all) at the bottom of a small pot of well-drained cutting mix, and keep them in the greenhouse, but not in a polythene bag as usual. It may take three-to-six months to root. On no account take it out of the pot to see what’s happening. Keep slightly damp but not wet.

The impressive Furcraea parmentieri which needs to be wintered in a greenhouse.

You may think it’s the ultimate extravagance, but I like greenhouses so much we now have two. The first came from Greenhouse Ireland and measures 3.1m x 3.84m, all glass, with a pretty metal Victorian detail on top, and was very good value. The next came from Gabriel Ash, a traditional cedar greenhouse with a lovely scent of wood, which I find very useful because the front half is a greenhouse and the back is the storage shed. A shed is essential for the winter storage of dahlias and cannas, plus all the piles of interlocking pots, stakes of every size, bits of string, wire, plant labels, tools and all the essential items that gardens are made of. Some people use the greenhouse just for growing tomatoes, others want one for veg or overwintering exotics. Don’t feel guilty if all you want is a quiet sit-down with a book – I can spend many happy hours doing very little, just watching the day go by.

I have one especially fascinating South American plant that I couldn’t possibly grow without a greenhouse, namely Furcraea parmentieri, which is too tender for winter outdoors. When it flowers, spectacular isn’t in it. The flower spike is ten feet tall, bedecked with a mass of pretty little yellow flowers which gradually develop into fat little green baby plants, scattering in every direction. They are collected and sown in the greenhouse. It takes five years until they bloom; around February you will notice the centre of the plant (is around four feet in diameter and is expanding rapidly).

A couple of other special plants well deserving of a greenhouse in winter are Musella lasiocarpa and Hagenia abyssinica. The former is the hardiest known banana, but unlike other bananas, with leaves that get shredded in the wind, this one’s leaves are pristine until autumn. The hagenia is a most beautiful evergreen tree from mountainous regions of central and eastern Africa.

Helen Dillon has been gardening for 45 years and her most famous garden was in Ranelagh in Dublin. She is now embarking on a new garden in Monkstown, and it is the subject of a talk with the Irish Georgian Society on Tuesday April 17 at 6.30pm;

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