They craved greenhouse wisdom, and found it on a wet Wednesday in Wisley. Helen Chappell was in the class, notebook at the ready, at an RHS lecture
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A WET Wednesday: am I insane or is this a sensible time to attend a lecture on "Growing Under Glass" at the RHS garden at Wisley, Surrey? It's reassuring to find Wisley flowerbeds a sea of brown - neatly pruned roses, well-trained climbers, but not much of the apocryphal "winter colour" experts nag about every autumn. Couple of winter-flowering cherry trees. Pile of steaming dung. Soggy-looking gardeners in anoraks. I think of my own garden with its impromptu moss lawn, smell of cats, rotting cardboard boxes, and feel better already.

Man on the gate said to follow the yellow arrow signs to find the lecture hall. A bit like a treasure hunt on Boxing Day: unpleasant, but you must be a sport. Arrows so discreet I get lost right away. Rain beats down on head as I complete third circuit of rose garden, twice round fountain and end up in greenhouse. Goldfish in pond look smug. Youth under palm tree directs me down dank alleyway to potting shed. Visions of lush sub- tropical venue evaporate. Find self in small aircraft hangar full of old watering cans.

Ten minutes until the start of the lecture and six people have turned up. Rows of unfilled plastic stacking chairs. Demonstra-tion table piled with flower pots, sacks of compost, blood, fish and bone, bottles of Derris dust, Rapid bug-killer. Chaps in damp anoraks with golfing umbrellas arrive, along with elderly ladies with buns and pearls and young man wearing Barbour and wellies. Steam rises gently from moist bodies in the chilly room. Notebooks and pens at the ready.

Lecturer appears: friendly sort, Mormon haircut, nice green jumper, sensible shoes. "It's so quiet in here it's like you're waiting for a church service," he quips. Teeth chatter, nervous laughter. The audience numbers are up to a dozen now. Lecturer writes letters TOA on blackboard. T is for timing. "We're all getting a bit interested in our gardens now, aren't we?" he says. Deathly silence. "The sap is rising, isn't it?" He moves on to letter O for observation. Watch greenhouse plants like hawk, he counsels. Thou shalt not suffer a whitefly to live. A is for action. Don't put off till tomorrow what you can blast with Derris dust today. More wet bodies arrive. Numbers up to 20 now. True British grit.

Which brings us to peat, loam and coconut: the vexed question of potting compost. Tutor plunges his hands into plastic bowls of muck, face a picture of sensual joy. He invites us to come up and cop a feel at end of lecture (mental note: not a good idea). Q: Is loam better than peat? A: For long- term planting only. Is coir compost more pleasant to handle? (He fondles small pile to demonstrate.) Does it "slump off" and lose air holes with age? (Don't we all?) Tutor comes down in favour of a mixture of peat and pulverised bark. Much scribbling in notebook. Warns us not to hoard unused compost from last year - it goes nasty and stinks of ammonia. Kills baby plants. Faces slump off in disappointment. Make note to destroy sacks of unopened potting compost filling my airing cupboard. This is getting expensive.

To nourish greens, demand-feed hungry seedlings as early as week four. Sleepless nights working out the best ratio of nitrogen to phosphates to potash. Percentages and dilutions. Seed trays crying out for magnesium and trace elements. "You can't just pick up any bottle off the shelf at the garden centre," warns the lecturer. Oh God. Some formulas are for foliage, others for flowers and fruit. He advises a low nutrient multi- purpose liquid used little and often in summer. Blood, fish and bone is less a revolutionary slogan than a cheap option for organic souls. Slow- release granules are for lazy types like me.

Someone in the audience brings up pests and diseases (there's always one in every classroom). "Grow anything under glass and you're asking for trouble, aren't you?" accuses the tutor. Guilty looks and downcast eyes. But pests are devious and ruthless. They sneak into the coldest greenhouse to overwinter. Red spider mite lurks in bundles of canes, snug as a bug in bags of vermiculite. "I may be preaching," preaches the tutor, "but the only answer is to scrub everything down with Jeyes Fluid every year." Blood drains from faces of audience. Tutor on a roll now, advocating scraping algae from glazing bars with credit card or old toothbrush. "One per cent loss of light equals 10 per cent loss of growth," he cries. I must examine everything for fungal blight. Never take plants from strangers. Tell the next-door neighbour to stick his free cuttings.

Now it's demo time and the lecturer is doing nifty things with seed trays - twirling dibber and firming board, tweaking cotyledons. We learn: how to prick out, how to pot up, how to pot on and (finally) how to pot off. I scribble down: never pick up a seedling by the stem, never shake off soil, always use a module tray and drape gently with horticultural fleece.

Wildly rustling foliage announces a staking and tying section. The tutor wrestles with a 5ft weeping fig. Finally subdues it into a new terracotta urn. Dire warnings about polypropylene string as a horticultural murder weapon. How to whittle a pointed stick. Then stake-driving for beginners (crucifix optional). Only use aerosol leaf shine if the Queen is coming to tea. Any questions?

Members of audience fire off queries: is my datura potbound? Can I trust my water butt? Is foliar feeding a good idea? (No, it isn't). As rain continues to drum on the roof camaraderie emerges. We start to chat each other up. Lady next to me reveals she is professional gardener (eight gardens in London), used to be on the stage (understudy for Look Back In Anger) and work for the BBC. Are we mad to turn out in February for this sort of thing? "It's such a piss awful day," she says, "what else could you do with it?" She gives the lecturer high marks for stage presence, authentic rural accent and endearing apologies to manhandled plants. Her companion is an amateur gardener who opens her garden under the Yellow Book scheme, opens ftes and runs committees. She lives locally, pops into Wisley "to see what's out" and pick up hot tips. "I never thought about bark chippings as pot drainage." Me neither.

Young man in Barbour turns out to be the estate gardener for a country house: "You never stop learning, do you?" He has eight acres, two 150ft greenhouses and packets of seeds from RHS gift shop. Boss sends him here for "in-service training". He vows to stop recycling potting compost. Shows us his salvia seeds.

I dash through the rain again, trying to avoid waterlogged grass. Keep off the grass. Get lost in rose garden. Get lost in gift shop. Get lost in car park. Get wet everywhere. Feel a true gardener, virtuous and dedicated. Out in all weathers, sitting at the feet of experts. My notebook is full of handy hints and rude comments about people's clothes. I'm hardier and wiser. Bolder and wetter. Much wetter. Really very wet indeed.

! For details about RHS lectures at Wisley, phone: 0483 224234.