This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
A genus of evergreen dwarf shrubs, natives of Australia, producing their flowers in great profusion in this country during the spring and summer months. All the species in cultivation are of a free and compact habit of growth, and under good management the plants retain a neat shape, and continue in vigorous health for several years. The flowers of all the species that I am acquainted with are white or pinkish-white in colour, and spring from the axils of the leaves on the previous year's growth. The individual flowers are not large, but the profuse manner in which they are produced on healthy plants compensates for their want of size individually, and renders the plants when in bloom objects of much beauty. The flowering season of the various species extends from February to September; and plants of particular species keep up a constant succession of flowers for at least two months from the time the first blooms expand on the plants.
Amongst the first to open their flowers in early spring are E. scaber and E. pulchellus. Both these species are extremely free-flowering. E. cuspidatus is the latest to flower. As a rule, this species does not commence flowering before the end of April or beginning of May. It and E. buxifolius are of a more vigorous habit of growth than most of the other species, hence they are employed as stocks on which to graft the less vigorous kinds.
As plants for greenhouse and conservatory decoration during spring and early summer, Eriostemons are deserving of all the attention that can be given them, and when large enough, and in good condition, they are amongst the best of exhibition plants. Their symmetrical style of growth and profuse flowering qualities, combined with the length of time the flowers retain their freshness and beauty on the plants, render them highly suitable subjects for the purpose of the plant - exhibitor. Like some other genera of New Holland plants, Eriostemons have been partially neglected in recent years, both for the purpose of home-decoration, and as exhibition plants. I am of opinion, however, that at present a desire is becoming prevalent amongst gardeners generally, to give more attention to the culture of the class of plants indicated than they have been doing for several years past; and the desire is in the right direction, and should be encouraged.
The quickest, and, all things considered, the cheapest way to get a stock of the plants under consideration, is to procure them from a nursery. Nice little healthy plants, in a flowering state, can be purchased for about 5s. each. When they arrive from the nursery they should be in a healthy condition - if not, the purchaser should return them at once. The reason why I advise this is, that these plants, when through any cause they get into an unhealthy state, seldom become healthy again; and therefore healthy plants only should be selected to start with.
The compost which I have found Eriostemons to thrive best in consists of sandy loam, and bits, about the size of large peas, of broken sandstone, in the proportion of three parts in bulk of the former to one part of the latter. It is very necessary to supply them with ample drainage at the roots. It matters not how careful the cultivator may be in attending to their wants in other ways, if he neglects to provide a ready exit for superabundant water from the roots of the plants, the result in the end will be disappointing to him.
If the drainage keep in good order, the plants will not require repotting oftener than once in two years, and the time to do so is soon after they cease flowering. When they are being repotted, the fresh compost should be made firm about the balls containing the roots, and the latter disturbed as little as possible during the process. After being repotted, they should be placed where they can be shaded from direct sunshine, and where they will not be subjected to draughts of dry air for a week or two. A cold pit or frame is a suitable place for them at this time; and indeed a structure of this kind is as good a place as any in which to grow these plants during the summer months. The principal things to be attended to while they are in the cold pit or frame are, to see that they are supplied with water at the roots on all occasions when it is necessary, and that, after the first two weeks, a supply of fresh air is continually admitted to the structure. About the end of September the plants should be removed from the frame or pit to the greenhouse, and placed in as airy a position and as near to the glass as circumstances will admit of.
During the winter season the cultivator must be careful in the matter of applying water to the roots, as an over-supply is fatal to the health of these plants : on the other hand, the soil about their roots must not be allowed to become dust-dry. The plants should therefore be carefully examined at short intervals, and the condition of the soil at the time, as regards moisture, should determine whether water at the roots is required or not. Of course the decision in this matter rests with the cultivator; and the more correct his conclusions are on this point, the more success will attend his efforts in the culture of these and other plants under his care.
In the matter of staking and training, Eriostemons require little labour. A central stake to each plant is generally all that is needed. In some instances it may be desirable to employ more than one stake - the fewer, however, the better; and whatever number is used, they should be arranged so that they will be as little seen as possible.
As regards insects, Eriostemons are not exempt from them. Greenfly, thrips, and brown and white scale will attack these plants. The two first are not difficult to keep in subjection, as strong fumes of tobacco kills them; and as the plants are not easily injured by tobacco-fumes, the latter can be made strong enough to vanquish the enemy. The scale is not so easily got rid of if it once gets thoroughly established on large plants. With the aid of paraffin-oil, however, mixed with water, in the proportion of a wine-glassful of the former to a gallon of the latter, scale can be prevented from injuriously affecting the plants. The best time to apply paraffin-oil as an insecticide to all plants is when they are in the least active state of growth. If I am not mistaken, it was the editor of this journal who first brought paraffin-oil as an insecticide under public notice, and since then I have been using it as such. I find, however, that much caution is required in applying it to all plants, and especially to soft-wooded subjects, when in a growing condition.
According to Mr Dewar's remarks on paraffin-oil as an insecticide, in the February issue of the 'Gardener,' he has had much success with it as a destroyer of mealy-bug, and I have found it of great service in the same direction; but I cannot say that our "plants of Ixoras, Grotons, Gardenias, Hoyas, and others, have been thoroughly divested of the enemy by this means." And I am of opinion that nothing short of "utter destruction of the plants" would entirely rid large plants of Gardenias and Ixoras of mealy-bug, when it has got thoroughly established on the plants. T. Hammond.