The auriculas are flowering now - little plants with a great big past. In case you are not familiar with these dainty, carnival-coloured characters, they are the descendants of a hybrid that arose naturally between two species of primula from the European Alps: the golden yellow Primula auricula and the rosy pink P. hirsuta.
Their offspring, Primula x pubescens, has flowers ranging from white, yellow and pink through to purple, red and brown. It was discovered in the late 16th century and immediately captured the imaginations of botanists, who began to collect, select and further breed the different strains.
Now, after centuries of human intervention, there are hundreds of charmingly contrived varieties of auricula, utterly removed from their natural parents. If you were being fanciful (and I'm afraid that the perky charisma of auriculas drives you to the most awfully indiscriminate flights of fancy), you'd say that somewhere along the way they had been crossed with liquorice all-sorts, old chintz upholstery and those nicely crazy silken outfits that jockeys wear.
You'll see what I mean if you pay a visit to the auricula collection (under the care of Barbara Cunningham and Anne James) at the Talbot Botanic Gardens at Malahide Castle in Co Dublin. A turn-of-the century alpine house in the walled garden is where you'll find them: their artfully painted primula faces rising out of hundreds of small terracotta pots, and flaunting the kind of irreverent colour combinations that are the work of a child let loose with a new paint kit. "Sirius", for instance, has a yellow bull's eye surrounded by a deep-purple band bleeding into an avocado-green border, and "Lovebird" (one of the classics) sports a perfect circle of white "paste" ringed with jet black and green. The paste, a granular substance - also known as "farina" or "meal" - is much prized, and as it is washed away by rain, paste-clad auriculas must be grown under glass.
At Malahide, white horticultural fleece masks the windows of the glass-house, excluding harsh sunlight, but also creating a private and secretive place for these botanical curios. And even though a healthy breeze wafts through at all times (except when frost or fog is forecast and the vents are closed) a sweetly subtle smell of lemons, honey and history hits you when you enter the door. Auriculas were greatly admired in this country during the 18th century: the sixth Earl of Meath grew dozens of them at Killruddery in Co. Wicklow, and they were also grown in Trinity College's Physic Garden. New varieties of auricula - and carnation also - were feted at meetings of the Dublin Florists' Club, a bibulous but well-meaning society of gentleman plant-breeders, founded in 1746. After being named and approved, the new auriculas, formally displayed on a mahogany stand, were ritually toasted (but only after several rounds of salutations to the various members, alive and dead, of the Royal Family).
In England, meanwhile, auriculas were exhibited with even more pomp: in carefully lit miniature theatres upholstered in black velvet. Special composts were concocted to nurture the best blooms. One of these, favoured by a 19th-century London florist, Isaac Emmerton, was composed of "goose dung steeped in bullock's blood, baker's sugar scum, night soil and yellow loam".
At Malahide nowadays, however, a mixture of three parts peat and one part sand, sweetened with a dash of lime and nourished by some slow-release fertiliser granules seems to work a treat. And according to Barbara Cunningham (who is so auricula-besotted that her currently-being-decorated house is in danger of ending up auricula yellow), they are dead easy to grow provided they are well-ventilated, protected from strong sunlight and kept just moist during their growing season. In winter the compost is gradually dried off as the plants barely tick over in the colder months. (Of course, not all auriculas need to be grown indoors. "Old Irish Blue", for example, is a much sought-after border variety - which comes in at least two distinct forms. If you see it at a plant sale, grab it.)
But the best thing about auriculas, says Cunningham, is that crossing them is simple, and because their genes are so richly diverse, anything can pop up. "Buy two, start to cross them, sow the seed and you never know what you will get!"
Anyone who doubts that need only look at the motley, but exuberant, crew in the 400plus pots at Malahide. Almost all of these are the results of two years' unscientific - but very enthusiastic - breeding.
Malahide Castle's walled garden and auricula house may be seen only on guided tours, which normally take place at 2 p.m. every Wednesday until September 30th. However, to facilitate readers of this column, additional tours will take place at noon and 3 p.m. for the next three Sundays (May 16th, 23rd and 30th). Special group tours by arrangement. Fee: £2.
The rest of the Talbot Botanic Gardens at Malahide Castle is open daily 2-5 p.m. until September 30th (01-8462456).
A range of auriculas is available from Timpany Nurseries, 77 Magheratimpany Road, Ballynahinch, Co. Down, BT24 8PA (tel./fax: 08-01238-562812).