Erysimum Pumilum.

Fairy Wallflower, or Dwarf Treacle-mustard; Nat. Ord. Cruciferæ.

One of the alpine gems of our rock gardens, not in the sense of its rarity, because it grows and increases fast. It came from Switzerland about sixty years ago, and for a long time was esteemed as a biennial, but it is more—it is perennial and evergreen; at any rate its new branches take root, and so its perennial quality is established. Let the reader imagine a shrub, 3in. high, much branched, and densely furnished with pale green foliage, which hides all its woody parts, forming itself into cushions, more or less dotted over with minute canary-yellow flowers, and he will then only have a poor idea of the beauty of this pretty alpine. It flowers in summer, autumn, and winter, and in certain positions both its habit and flowers show to most advantage at the latter season. At no other time during the year have my specimens looked so fresh and beautiful as in January. This I have proved repeatedly to be the result of position, shortly to be explained.

The flowers are produced in terminal racemes, are scarcely ½in. across, cruciform in the way of the Wallflower, greenish-yellow, and delicately scented. The leaves vary in shape on the various parts of the branches, some being lance-shaped and others nearly spoon-shaped; the lower ones being all but entire, and the upper ones, which are arranged in rosettes, distinctly toothed. They seldom exceed an inch in length, more often they are only half that size, but much depends on the position and soil. In summer the foliage is greyish-green; later it is almost a bright or clear green, the latter being its present colour. The habit is branching and compact, by which it adapts itself to crevices and uneven parts in a pleasing manner; and not only does it best adorn such places, but from the fact of their dryness, they are better suited to the requirements of this little shrub.

A sandy loam, such as will not bake, suits, and if mixed with a[Pg 98] few stones all the better—this will be found ample food for it; poor soil and a dry situation grow this subject in its finest form. I may perhaps usefully give the method by which my specimen is grown, after experimenting with it in various parts of the garden, and also the substance of a few notes I made of it. In pots the fine roots soon formed a matted coat next the sides, when the foliage would turn sickly and yellow, so that, useful as the practice is of growing alpines in pots, it does not answer in this case. On rockwork, in vegetable soil, this low shrub grew taller, being less woody, and was killed by severe weather. On the flat, in borders, in rich soil, it did well for a season, then damped off, a branch or two together. On the flat, in sand alone, it does well, also on the top of a wall, such being a position especially provided for hardy sempervivums and a few cacti. A bit of the Fairy Wallflower was tried there in a thin layer of sandy loam, and for two years my finest specimen has occupied that position, flowering more or less throughout the winter. Where there are old walls or rockwork it should be introduced. A ready and effective way of planting it is to get a sod of grass 3in. thick; measure with the eye the size of the interstice in the side of a wall, partly cut through the sod on the earthy side, open it by bending, and insert the roots of a small specimen; close up, and cram the planted sod tightly into the selected opening. In one season the shrub so planted will have a snug and pretty appearance. It is self-propagating, from the fact of its lower branches rooting where they touch the soil. These may be taken any time and planted separately.

Flowering period, April to winter.