This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
The ensuing remarks apply to the larger towns, where the sooty deposit from the immense volume of smoke daily manufactured by the numerous fires renders it impossible to grow many plants that would otherwise flourish. There are, of course, other causes beside the smoke tending to destroy vegetation, or prevent the luxuriant growth we find in the open country, amongst which we may name drought. But as smoke is by far the worst enemy the gardener has to encounter in and around large towns, it will suffice to point out the most suitable subjects for planting in such localities to resist its evil effects. All plants suffer more or less, and, therefore, we have only to choose those which by nature are the least liable to injury. Evidently deciduous trees and shrubs possess an advantage over evergreen species in the total annual renewal of their foliage. Hence it follows that deciduous species should as a rule have the preference. But species with deciduous foliage are not all equally suitable, though this depends perhaps nearly as much on the moisture within reach of their roots, as upon the deleterious effects of an impure atmosphere. Taking London as an example, it will be seen that certain trees and shrubs grow freely, and for a month or two retain the freshness of spring. The Plane stands first in this category, and being a handsome umbrageous tree should be freely planted. The Common Ash, Poplars, Laburnum, Thorns, several species of Pyrus, Ailanthus glandulosa, and the Elm, also thrive satisfactorily, taking the adverse conditions into consideration. The Lime is a very handsome tree, but it is so frequently infested with caterpillars, which destroy the beauty of its foliage in early summer, that it cannot be recommended for town planting. Where the open space is considerable, many other species may be added, such as the Maples, Horse Chestnuts, False Acacia, and Turkey Oak.
Evergreen shrubs should not be altogether excluded. Those with smooth glossy leaves, like Aucuba Japonica, Ligustrum latifolium, Rhododendrons, Box, Euonymus, Thujopsis dola-brata, and Ivy, succeed best, owing to the action of the rain being more effectual in cleansing the epidermis than in those species with hairy foliage. The same remark applies to herbaceous plants. Thus Tulips, Hyacinths, Narcissuses, etc., may be successfully grown, provided the other conditions be favourable. Tufted evergreen herbaceous plants, on the other hand, will not answer so well. Helleborus orientalis, Eranthis hyemalis, Iris Germanica, Sweet William, Chrysanthemums, Candytuft, Mignonette, Virginian Stock, are amongst some of the easiest to cultivate in crowded quarters. It is almost unnecessary to mention that much may be done to keep plants in health and vigour by free use of the syringe and a good lookout after vermin. Sometimes a batch of annuals will disappear almost as suddenly as if a flight of locusts had visited them. The fact is, the moths frequenting such places are very numerous in proportion to the vegetation, and consequently unless the caterpillars are sought out while they are quite young they rapidly devour everything green within their reach. In conclusion, we may observe that plants, like animals, require extra care and attention under artificial conditions; and only those who really delight in the beauties of nature will undertake the culture of their favourites under such a combination of adverse circumstances as we find in the midst of our smoky towns.