When it is remembered that north of the 50th degree of latitude the vine yields little but garlands of leaves, and that we should attempt in vain to cultivate the olive north of the 44th degree, it may seem strange that the Lavandula vera, which is a native of about the same climate as these, should resist, unprotected, the vigorous frosts of this country.  Even at Upsala, latitude 59 deg. 51’ N., in the Botanic Garden, it merely requires the shelter of a few branches to protect it in the winter; but this hardiness may be accounted for by several physiological reasons.  Like all fruticulose labiates which have a hard compact tissue and contain much oily matter, the lavender absorbs less moisture than herbs which are soft and spongy, and, as it always prefers a dry calcareous, even stony, soil, the northern cultivators find that by selecting such localities the tissues of the plant take up so little water that the frost does not injure them.

In a northern climate the length of the days in summer, and the natural dryness of the air, compensate in some measure the reduction of temperature, and mature the plant only to the extent sufficient for the purpose for which it is grown.  Perhaps the suspension of vital action during winter, which must be more complete in northern latitudes, as our frosts are more severe, tends to preserve certain plants, native of the south, for it is observed that all plants are more sensitive to cold when vegetation is active than when it is at rest.  The vine is an instance of this.  On the other hand, when the plant is cultivated further south than its natural boundary, the same causes seem to exert their influence, but in the reverse sense.  Lavender is cultivated on the mountains of Yemen, in Arabia; the humidity, increasing inversely to the latitude, compensates the exhaling force of the sun’s rays, and the elevation of the locality the effects of the heat.

Thus is confirmed, both in north and south, the law of vegetable physiology observed by De Candolle, in the temperate climates of France, and published in his “Essai de Geographie Botanique,” that “plants can best resist the effects of cold in a dry atmosphere, and the effects of heat in a humid atmosphere.”  A mild, damp winter, like the one of 1889-1890, does more harm than a hard, seasonable frost, as the plants are apt to make green shoots prematurely, and the late frosts nip off these tender portions, each of which would otherwise have produced a flower spike.

The very severe winter of 1890-1891 did not kill so many plants as the one of 1889-1890.  The stems and branches of lavender being ligneous and strong are able to resist the force of the wind, and the plant thrives best in a perfectly open locality, where the air circulates freely; the oil and resin which it contains in abundance enable it to resist the parching action of the wind and sun.  Thus, on the most arid and sterile ground on the mountain sides in the south, and especially in Spain, plants of this genus flourish with more vigor in the season when most other vegetation is scorched up by the ardent rays of the sun, and the Lavandula vera seems to have a predilection for such spots.