Flora Anomoia: A General View of the Anomalies in the Vegetable Kingdom pp. 128-129 (1817)
Fragrance and Soil
By Thomas Hopkirk

* Pursh.
Sir E. Smith in Lin. Trans.

In double flowers, the smell or flavour is generally much increased, which frequently arises from the multiplication of the petals. These containing in general more of the volatile oil, the source of the odoriferous emanations, than the other parts of a plant, being increased in number, the odour is also increased. It has been said indeed, that abundant nourishment, by filling the pores with juice, and enabling the plant to secrete more of the oil from whence the perfume arises, may tend to heighten its flavour. Thus the odour of Thyme is much stronger when cultivated in a garden. But the reverse of this frequently takes place. The Water Cress, (Sisymirium nasturtium,) and Mentha rubra, have a much more aromatic smell, when growing in dry, than in wet soil, and in fact no general rule can be laid down as to these differences. The herb Robert, (Geranium Robertianum,) in America wants the heavy unpleasant scent, so remarkable in the British species*. The Common Frog-bit, (Hydrochuris morsus ranae,) varies with scented or scentless blossoms, and the same thing takes place in the Persian Cyclamen, (Cyclamen persicum.) Almost every Mint, says Sir Edward Smith, has a peculiar smell of its own, in its original wild state, by which it is known from its congeners. Thus Mentha arvensis, by its smelling like blue mouldy cheese, is distinguished from the other whorled Mints. But many Mints are capable of acquiring an entirely new smell, by change of soil, a dry situation, or by some change in their constitution which we do not understand. Thus the smell of Sweet Basil is acquired by some, that of the Orange by others, and one or two acquire a sweet smell, which belongs also to a sweet variety of the garden Thyme, called in Norfolk, where it is common, Frankincense Thyme, and the Pepper-Mint, the taste and smell of which is so well known, is by those who cultivate it for medical purposes, taken up and transplanted every three years, otherwise it degenerates into the flavour of Spear-Mint, from which nevertheless it is specifically different†. There is in every plant, when in a natural state, a particular constitution which enables it to apply the juice it imbibes to the formation of its own qualities. Hence, says Dr. Hunter, "a mass of innocent earth can give life and vigour to the bitter Aloe, and to the sweet Cane, to the cool Houseleek, and to the fiery Mustard, to the nourishing Wheat, and to the deadly Nightshade." Accidental circumstances may sometimes alter or destroy those peculiar qualities, but the cause being removed, the plant will generally resume its natural properties.