This section is from the book "The Gardener's Monthly And Horticulturist V21", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
The Cape Heath genus, Erica, is esteemed by all lovers of Flora as one of the finest of greenhouse plants, and should be found in every collection of any extent. I however, find it a prevailing idea in this country that the Heath cannot be cultivated owing to the nature of the climate. This I think is not the case, as by comparing this climate with that of the Cape, there is not so great a variation. The atmosphere here is quite as pure as that of the Cape, and the Solar Heat does not differ so much as to materially effect that beautiful tribe of plants if they are tended with care and unremitting attention. I have been with the late Mr. MacNab, of the Royal Botanic Gardens, Edinburg, for a number of years. He was, I may say, the first and greatest of Heath growers, for I have never seen bis fine specimens eclipsed either in Scotland or England. I have thought a few hints of his superior modes of treatment might be useful for your excellent magazine, and stimulate growers of plants is this country to patronize this unique and beautiful tribe of plants.
The first and most important part of growing the Cape Heath, is the nature of the soil; it must contain a considerable quantity of pure white sand, say one-fourth part of a whole mixture will not be too much. The soil itself must be of a friable nature, not that spongy bog peat, but that found on high lying ground, which in Scotland is generally to be found mixed with fine white sand; but where this important ingredient is wanting, it can be replaced by pounding good free' stone, and mixing it with the soil to the extent recommended above. The plants are also greatly benefited by a quantity of free stone broken into small pieces and mixed in the soil, and also in the process of repotting pieces of the size of two or three inches of the same materials placed around the ball as the soil is filled into the pot. The value of these stones is very great in the process of growing the Cape Heaths, as in many instances they suffer from over moisture, when these stones help to absorb and again give out the moisture to the roots. If the cultivator resides in a very dry atmosphere, keeping the plant the whole year in a greenhouse is important.
Shelves ought to consist either of stone or slate slabs, as wood is very injurious to the plants in absorbing the moisture from the roots of the hard wooded varieties, - in particular, such kinds as Jasa-miniflora, etc. The drainage of the pots or tubs is also an essential part of the treatment of the Cape Heath. Whatever size of pot or tub is used for a plant, a fourth part of it should consist of clean drainage; that is either broken free stone or pots, and a nice layer of turfy peat on the top of them before placing the plant in position, which should be rather elevated then over deep. The treatment during the summer months must also differ from that of the general run of greenhouse plants; they must be so placed that they can be sheltered from heavy rains and scorching suns. The best mode of treatment we could suggest during the tropical summers of this country, is to choose some northerly aspect; and having some nice large roomy frames with sashes in readiness to draw on in the event of heavy rains, plunge the plants up to the rims of the pot, using fine sand to plunge in, which keeps the roots nice and cool. Pots set out in the open air unprotected from the hot rays of the sun get so heated that they destroy all the fine fibrous roots of the Heath tribe.
The treatment of the plants during the growing season, is also a most important part of their cultivation. If fine bushy specimens is the aim of the cultivator, he should give careful attention to supporting the stems with nice, green painted stakes - to such varieties as the Aristatias, Jasminiflora, etc., and all of that class; but the soft wooded varieties, such as Lenoides, Caffera, and all the Ventri-cosa section should have the young wood constantly topped as they grow to make fine bushy plants, and will do with few stakes, the fewer the better; for I think the remarks of the late Dr. Lindley were good, when he said " that a plant with a multitude of stakes was like a cripple who needed support." Indeed the fewer stakes that any of the varieties have, the better, and this important point in growing fine specimens may to a great extent be attained by regularly pinching the tops of the young shoots as they proceed in growth. During the growing season Heaths, of whatever variety, should never be cut back to the old wood, as in many varieties it will prove certain death, at least in all the hard wooded sections.
Some of the soft wooded varieties, such as the Caffera, Ventricosa, etc., may do to be cut back to a certain extent, but a much better plan is to shorten in the young wood, which in all the different varieties of the Cape Heaths, is sure to produce the best results. The treatment of the Cape Heath under glass during the winter, is a most important part of successful cultivation of this fine tribe of plants. They must not be crowded among other greenhouse plants, but stand clear by themselves, and the less the amount of artificial heat, the better, if the frost is barely kept out. Indeed, I have seen two or three degrees of frost in the Heath houses, of the Botanic Gardens, Edinburg, and air on them when the temperature out of doors was 36°. Mr. McNab had a very excellent plan of managing the heating apparatus in the Heath houses, by keeping the hot water pipes covered with sand, and when very severe frosts set in, he removed a portion as circumstances required to allow a circulation of heated air.
Since writing the above, I have had a conversation with Mr. Dawson, the curator of the Bussey Institute, who informs me that Professor Sargant, the director of that Institute, as also of the Cambridge Botanic Gardens, contemplates the very judicious experiment of getting seeds of the various native species at the Cape, from their correspondent there, and raising seedling plants which would result in a brood of real aclimatized varieties which would have all the vigor possessed by healthy seedlings, and would cross with some of the fine European hybrids, like McNabiana, Aristata, etc. I hope that the Professor who possesses a fine taste for floral studies, may carry out this excellent resolution.