A is for Alan Postill. Never heard of him? Well, if you're a keen gardener, you might be living with his wife. So to speak. Mr Postill is propagator at Hillier Nurseries and raised Daphne bholua 'Jacqueline Postill', named after his missus. This year, he introduces Choisya 'Aztec Gold', a new variety of the golden-leaved form of Mexican orange blossom. A is also for Alan Titchmarsh, inset, who will be presenting BBC coverage.
B is for Bees – bumble, honey or any kind – which play such a vital part in pollination. Look out for the Leeds University exhibit, which demonstrates bee-friendly gardening. B is also for betting. William Hill has Olympic garden designer Sarah Price at 7/2 to win best in show, closely followed by Cleve West (last year's winner) and Arne Maynard.
C is for Caravan, as featured in Jo Thompson's Celebration of Caravanning Garden for (who else?) The Caravan Club. It features a gleaming vintage 1950s model called Doris. C is also for the Chelsea Cough. Chelsea coincides with the plane tree pollen season – and there are lots of plane trees on site. Pray for weather that's not dry and windy.
D is for Duels. No, not a re-run of the spat between Diarmuid Gavin and Bunny Guinness a few years ago, but live displays by the Beazley British Fencing team, courtesy of Hillier Nurseries, who have supplied more than 2,000 British-grown trees to the Olympic Park. Hillier know all about gold medals – they have won 66 consecutive golds at Chelsea.
E is for Edulis nursery and exotic vegetables. Time was when you hardly saw a potato at Chelsea, but this year Edulis are going one better than the standard veg display and featuring unusual edible varieties such as duck potato (Sagittaria latifolia) and earth chestnut (Bunium bulbocastaneum).
F is for Fringe, the extraordinary series of events taking place all over London, organised by Tim Richardson, landscape critic and British gardening iconoclast.
There are no sponsors and only a band of volunteers, but so far they've managed to attract more than 70 events, which get under way today and continue until 10 June.
If you weren't able to get a ticket to Chelsea (which sold out in record time this year), you can find out what events are on where by going to www.chelseafringe.com. The events range from floating forests to community gardens to The Garden of Disorientation at Smithfield market.
G is for Glamourlands, created by artists Tony Heywood and Alison Condie, and described as a techno-folly. It's a sort of evolving landscape-cum-installation inspired by Dorset's Jurassic coast, and it marks the introduction of a new category of show gardens, called Fresh, which replaces the Urban Gardens class. Expect some harrumphing from the panama-hat brigade.
H is for high-rise – seven storeys to be precise. Diarmuid Gavin, responsible last year for Chelsea's first sky garden featuring a floating pink pod, has designed an 80ft pyramid this year, sponsored by Westland. Why? Why not?
I is for Imitation, in this case imitation grass, courtesy of Easigrass. They're supplying the fake turf for Tony Smith's Green With ... design, another of the Fresh gardens, which explores "the human emotions of envy and desire through colour form and plant history". More prosaically, imitation grass is also good if you're worried about dog wee damage.
J is for Joe Swift, who after years as a television presenter on the BBC's Gardeners' World as well as its Chelsea coverage, is designing his first garden for Chelsea. It's for Homebase and the Teenage Cancer Charity and it explores the difference plants can make to the urban environment.
K is for Korea, and the Demilitarized Zone (DMZ), which commemorates its 60th anniversary in July 2013. Designer Jihae Hwang, who won a gold medal last year, has created a garden inspired by the pristine vegetation which grows undisturbed in the Zone.
L is for Literature, which has provided plenty of food for thought at Chelsea this year. Adam Frost's garden, entitled A Rural Muse, pays tribute to the Northamptonshire countryside that inspired John Clare, the "Peasant Poet". Vicky Harris's Veolia Water Garden, inspired by William Wordsworth's poem The Fountain, recreates a Cumbrian landscape and explores ways of conserving water in the garden. And The Plankbridge Hutmakers Ltd Garden, designed by Adam Woolcott and Jonathan Smith, uses heirloom vegetables, British wildflowers and a handcrafted shepherd's hut to depict the opening scene of Thomas Hardy's Far From the Madding Crowd. No dead sheep, though – there wasn't a convenient cliff.
M is for designer Arne Maynard, one of the most influential figures in modern British gardening, who is making his return to Chelsea after 12 years. He won Best in Show for his first garden at Chelsea, in 2000, so he's set himself a high standard. His 2012 garden, for Laurent-Perrier, features an enclosure formed by pleached copper beech trees, and an ancient, enormous pear tree, as well as old roses.
N is for New Plants. There are new varieties of roses, irises and sweet peas, including – predictably – a David Austin rose called 'Royal Jubilee' (deep pink), a Peter Beales rose called 'The Queen's Jubilee Rose' (white, flushed peach) and a sweet pea from Eagle Sweet Peas called 'Diamond Jubilee' (white with a pink edge). N also stands for the Name of the show. Thought it was called the Chelsea Flower Show? In fact, its proper title is the Great Spring Show, and that has never been officially changed.
O is for the Olympics, which have managed to infiltrate the hallowed grounds of the Royal Hospital. Two designers involved in the London Olympic Park 2012 Gardens project have gardens at Chelsea – Sarah Price's garden for The Daily Telegraph conjures up the romance of the British countryside, while Nigel Dunnett's RBC Blue Water garden is a contemporary take on the traditional paradise garden. Instead of canals, there will be a rainwater management system involving bioswales, which filter surface run-off water. It's a neat idea, because in traditional paradise gardens, the channels or rills – representing the four rivers of paradise – also played a practical role in irrigating the garden.
P is for Phytophthera ramorum and Phytophthora kernoviae, two potentially catastrophic pathogens which are killing British shrubs and trees. The Food and Environmental Research Agency will be advising on how to stop it spreading, and you can pick up a test kit for your garden.
Q is for the Queen, who visits Chelsea at 3pm on Monday to view the gardens and exhibits. Will she order 200 Jubilee roses? I think we should be told.
R is for Ringo Starr, who will be opening the WaterAid garden. It will include a water pump, and features Sutherlandia frutescens, a southern African plant known as the cancer bush, which gives you a clue as to why ethnobotanists are getting excited about it. It is also thought to have the ability to boost the immune system, and could play a part in the treatment of HIV and Aids. R is also for Retreats, designed by five of Britain's best-known names, including Orla Kiely and Kaffe Fassett. If you've always wanted to turn your garden shed into a gorgeous haven, these will show you how. Tip: get rid of the cobwebs first.
S is for stars and s'lebs, who will be twinkling away for the cameras on Monday, the Chelsea press day. Gwyneth Paltrow will be there, and Kate Hudson, while homegrown regulars include Joanna Lumley, Rolf Harris, Dame Maggie Smith, Dame Helen Mirren and Stephen Fry.
T is for Trends, which brings us neatly to Topiary. Arne Maynard is using it, and Cleve West's garden for the investment management company Brewin Dolphin demonstrates the popularity of topiary in gardens big and small. Cleve is using clipped beech and yew, while Tom Hoblyn plans to use Osmanthus x burkwoodii balls for his Arthritis Research UK Garden, which is inspired by the gardens of Renaissance Italy.
U is for Umbrella, that stalwart companion of the great British day out. You'll need one. See W.
V is for Sir Harry Veitch, who in 1912 held an international horticultural exhibition in the grounds of the Royal Hospital, Chelsea. It was so popular that in 1913 the RHS moved its annual Great Spring Show to the Chelsea site. Plant Heritage are using the centenary as an opportunity to illustrate the life and work of Veitch and his contributions to horticulture. On display will be a number of plants introduced by Veitch's plant hunters, who were sent out all over the world to find species that would suit the British climate.
W is for Weather, always an issue at Chelsea. I'd love to tell you it's going to be glorious, but although the forecast is for warmer temperatures than of late – around 21C on Tuesday, with some sunshine – there will still be the risk of the odd shower.
X is for xeriscape, which is a posh word for a garden that doesn't require watering or irrigation. Drought has been a big issue in the UK this year – for inspiration on plants that thrive in dry conditions, have a look at the Fresh Climate Calm Garden and the L'Occitane Immortelle Garden.
Y is for Yorkshire, and designer Tracy Foster's garden celebrates the wild moorland around Haworth that fired the imaginations of the Brontë sisters. It's a shame David Austin's new 'Heathcliff' rose is not included in this miniature Wuthering Heights.
Z is for Zeitgeist. Many people think of the Royal Horticultural Society, organisers of the show, as old-fashioned at best and elitist at worst. In fact, the RHS monitors the spirit of the times very closely. It has to; as an educational charity, it investigates the impact of issues such as climate change, and also gauges how horticulture can best contribute to contemporary life.
Victoria Summerley will be covering the show live on her blog from Sunday 20 May. Go to http://victoriasbackyard.blogspot.co.uk/