INDISPUTABLY they are among the treasures of the winter, spring and early summer splash.

With colours stretching across the spectrum, shapes that induce the "aah" factor and a toughness that's up there with the leading cold conquerors, no garden should be without them.

It's got to be primulas!

They featured briefly in my Top Twenty plant profile last month. They were also the very first flower I wrote about when I launched Journal Gardening back in December 1979.

My words at the time were: "Primulas, those most brilliant harbingers of spring, are enjoying a surprised flash of colour in the winter garden right now."

Roll on a little over 32 years and, thanks to January's mild offerings, the same can be said of this extraordinary and complex floral family that spans somewhere between 400 and 500 species and 28 classifications.

Their natural domain is right across the Northern Hemisphere, chiefly the Himalayas, Tiber, China, India, Burma and nearer home in Austria and the Pyrenees.

And for all their positive attributes, the Horticultural Trades Association has named primula as its Plant of the Month for . . . yes, I'm two days late . . . January.

Many are rare and extremely beautiful, yet the average garden lover need concern himself with just a handful that you'll find on most plant shelves. Not forgetting countless hundreds of named varieties, particularly of Primula auricula, many of which look exactly the same.

Best loved of all is our delightful native primrose, Primula vulgaris, along with other primroses in various forms such as double-flowered, gold or silver-laced, the Wandas in claret red and several named varieties of the "common one" which tweak both colour and shape.

Other familiar faces include the cowslip, the similar-looking oxlip, auriculas, those "posh" Victorian favourites which can even be bright green, splashed or striped, and, of course, those old patio and border favourites, the polyanthuses.

All polys and primroses can be used effectively in bedding schemes alongside tulips, daffodils, muscari and other spring and winter arrivals.

The polyanthuses, which – unlike primroses – produce a cluster of flowers from one stem – embrace all the bright colours and look magnificent when set out en masse. They adore the sun but are happy in part-shade too, so long live versatility.

Never easy to grow from one year to another, Primula vialii from the mountains of China is a beauty with a pointed flower cluster in violet, around 18in high and with soft, hairy leaves. It will disappear in winter and, on the way to blooming the following May, the slugs and snails will be assembling. So be warned and have the ammo ready.

I love the candelabra types, the bright moisture-loving sparks of early summer. Characteristic in the way they grow in almost geometric tiers on sturdy stems, the candelabras will respond robustly in dappled shade and lime-free soil and will be happiest close to a stream or pond.

As for candelabra species, take your choice – bulleyana in orange, beesiana in pink-red, Inverewe in vivid red, cockburniana in red tinged orange, prolifera in golden yellow or dull violet and lofty pulverulenta in red-purple, all between 2ft and 3ft.

Don't overlook the drumstock primula, denticulata, that lives up to its percussion title with spherical umbels in yellow-eyed lilac, white or red-purple blooms. And do consider the elegant non-candelabras such as japonica Postford White or Miller's Crimson, secundiflora with one-sided, deep rose-red bells, alpicola with fragrant white, nodding yellow or violet blooms and capitata with dark purple tubular flowers above white-mealy leaves.

Bear in mind that all outdoor primulas relish their roots in humus-rich loam, though many will tolerate some lime. Many are easy from seed and, in the case of auriculas, awaiting the unfolding petals is always a tale of the unexpected as the outcome can be anything from blood-red, lilac, purple, cream, crocus-yellow or even a gorgeous combination of maroon and green.

I doubt if there is any garden centre that doesn't stock primulas of one or more sorts. If, however, you covet a collection of rarely-seen species, try one of the many specialists such as Kevock Garden Plants in Midlothian, Scotland (0131 454 0660 or online at kevockgarden.co.uk).