There are so many young gardeners -- new to gardening -- nowadays that I should say a word about obsessions that commonly strike the gardener without reason and without warning. If one is prepared, one copes better.

A thing that often happens is the gardener has been happy for two or three years puttering about, planting an azalea here and a tulip there, and thinking a good bit about hedges and fences and how the garden should be developed when time and money permit. Fine.

Then without much warning this hypothetical (and all too real) gardener stumbles into some plant that begins to obsess him, and thereafter (the disease usually lasts three years, but sometimes more in grave cases) has no happiness at all because he lacks this and that variety of whatever it is that has addled his brains.

Usually it is something like dahlias. His garden is fairly bare in late September and October and somebody springs a dahlia on him, or takes him to a garden specializing in those grand fall flowers. He sees great soup plates of scarlet and white and purple, he sees softball-sized smaller flowers quilled like the fretful porpentine, sees biscuit-sized flowers of unbelievable primness, all of these in every color (except blue) and loses his head. From then on he thinks only of dahlias, perhaps joins the local (National Capital Dahlia Society, 8103 Karl Rd., Alexandria, Va. 22308) group of dahlia fanatics.

What formerly sufficed, when dahlias were just an occasional blob of color in the background, becomes a full-blown passion, in which novelties are intensely desired, and endless thought is given to ideal methods of storing tubers over the winter, the precise moment of making cuttings (and whether 1 3/4 inches long is better than 2 1/2), etc.

Such a gardener is a trial to family and friends, because all of a sudden dahlias seem to enter every conversation.

The gardener may not go mad for dahlias. It may be daylilies. That is common. So are roses. And it sometimes happens that after the dahlia fever has subsided somewhat, the gardener goes hog wild for the iris or the daffodil.

I have great sympathy both for the gardener and his family in these cases. I have been through a variety of obsessions and survived them all. Indeed, I would have said I was now immune to this kind of thing.

Unfortunately, the Woodlanders catalogue arrived. I am finished with cyrillas (there was a time I was slightly berserk until I had a cyrilla, a lovely native semi-evergreen shrub the leaves of which turn red in December) so I passed over that listing without covetousness.

Then I saw the kadsura (K. japonica) that I had put out of my mind for almost 20 years now. I used to grow it, and a lovely vine it was, with oval evergreen leaves, flowers like tiny magnolias and pretty red fruit. The new growth is red, but the thing is, it is a vine of such elegance and refinement that any plantsman gravitates to it immediately. It is not terribly hardy (books say) but mine endured several below-zero winters without harm, out in the open, not against a wall.

The shock of seeing it listed again softened me up dangerously. Then I saw Ampelopsis arborea, like a Virginia creeper, only the leaves are more divided and fleshier. I used to grow that, too, and a strange longing came over me to have it again. This sort of thing is common in men of middle age and over.

But what really did the damage was a listing for Dasylirion texensis. Dasylirions are like yuccas, only the leaves are more like quills -- that is, they are more slender than yuccas and to me have an exciting look. I have never seen this plant listed for sale before. Needless to say, before I get round to ordering it, it will be sold out, as this nursery has only a handful of each of the many kinds of plants it sells. But even to know it is more or less available in the trade, now, is a great comfort to me.

One trouble with these gardening obsessions is that the plant being sought seems rather reasonable in price, so while you're about it, why not try a few other things? This way lies not only madness, which is all right, but financial ruin, which is not.

Hesperaloes are terribly nice. But my Lord, look at all the nolinas they've got. Now there is a real find. And that variant of our wild phlox, 'Pink Ridge.' And the blue-leaf form of Serenoa repens, the saw palmetto, which is such a weed of southern pastures, and which I have always loved as one of the most beautiful American plants. (Not fully hardy, perhaps, but certainly worth trying, and if you once get it to a large size you have it made in Washington.)

And the white form of one of our American wisterias (the ones in gardens are Chinese and Japanese varieties, but in the 18th century Americans grew Wisteria frutescens). It is not showy, or not nearly as showy as the usual wisterias, but very elegant all the same. It grew all over a Tuscan column in the garden when I was a kid, and its great twisted stem and big roots sheltered a family of five-lined skinks for more than half a century).

And look here, here's Smilax smallii. Never could transplant it successfully and had to admire a neighbor's. But if I get a pot-grown plant, surely it will do just fine? And the selaginellas, how hard it is to find them in Yankee places. And wait -- O by golly --

I had thought I was immune to the itch to possess. I am mature and am way past such follies. Until -- O, alas.