Splendid examples they were, of which the like are seldom seen now, and though we may not wish to own such leviathans of their race, yet it would be a great pity to let such fine things be forgotten.
Perhaps when we remember that Azaleas and Camellias may both be included in the ranks of hard-wooded plants, the cultivation of which most possessors of a greenhouse have attempted, an effort to grow others may not appear quite so formidable. At any rate, some of them are so well adapted to the cold greenhouse that they are worth any pains that can be taken with them.
By way of parenthesis it may be as well to remind the unbotanical reader that Azaleas are now ranged under the generic name of Rhododendron, a change which is rather puzzling until one gets used to it, for writers in garden literature are now taking into use the more accurate term ; but for gardening purposes the old name of Azalea is too firmly fixed in popular speech to be easily discarded and therefore is retained here.
To begin with, the well-known Azalea indica, which always suggests a hot-house, is by no means greatly addicted to heat. Large bushes in perfect health and flowering freely may be found growing in the open air in many parts of the country ; yet they must be set down--with most of the other plants which come under this heading-as belonging to the half-hardy class that are grateful for protection from actual frost, chiefly because their fragile flowers are easily spoilt by bad weather, and besides, for the greenhouse we want flowers before their due season.
To induce them, therefore, to open their buds during winter or spring, as the case may be, they must be specially treated. Azaleas set their flowers so early in the autumn that we can safely predict the amount of flower to be expected from them. This process once accomplished, for which it is necessary that the wood be well ripened in the open air during the summer, it is mainly a question of bringing the plants into snugger quarters, earlier or later, according to the time they will be required.
The greater number of the Azaleas we see in our greenhouses have been reared in Belgium, where the process of grafting is carried on systematically on a large scale. I gained a great deal of practical information a year or two ago through the courtesy of Mr. F. Sander, who spent some time in taking me over the very interesting nursery belonging to the firm at Bruges.
The small standards when they have reached sufficient maturity are planted out in prepared beds every season; where they make sturdy growth and ripen their wood. Those that are strong enough set buds on every branchlet during the summer, and are lifted in September, with as little disturbance of the balls of roots as possible, to be sent away to other nurseries. The smaller plants are placed again under glass close together upon stages and packed in with fresh soil. Here they grow on slowly but steadily through the winter until planting-out time returns once more.
Why should we not adopt some modification of the same system, even though we may have but half a dozen plants of the kind to care for ? A small space of prepared ground in suitable position is all that is needed, and after planting, but little attention would be required beyond watering in dry weather. I am convinced that many small greenhouse shrubs would be much safer, and the new roots would get more feeding and consequently, give better results than if kept starving in pots all the year round.
At any rate all kinds of Azaleas-A. indica, A. sinensis (= A. mollis) and the Ghent hybrids may be so treated to their great advantage. Firm potting is essential, and not over much pot-room, a point on which most novices make a mistake.
It may be a little doubtful whether the same treatment would answer with Camellias, on account of a tiresome trick of dropping their flower-buds, which usually happens just after they are brought under glass from their summer quarters.
Camellias are, in reality, hardier than the common Laurel, yet they are generally reckoned as greenhouse plants, probably for the reason that their early flowers do not stand either frost or wet.
They succeed best, undoubtedly, where they can be planted out under glass, for which their evergreen habit peculiarly fits them, as they are never unsightly. The single and semi-double kinds are by far the most interesting as well as ornamental, and there is a charming little white species (C. Sasanqua alba) which is well worth growing.
When grown in pots, after they have made their new leaves-not before-they should be plunged out of doors in a semi-shaded position, which in their case is better than full exposure to the summer sun, and they must be carefully attended to with regard to watering. When it is time to take them in, about October 1, a gradual transition from open air to frame, and from frame to greenhouse, will generally overcome the dropping tendency.
It is perhaps a little difficult to define the exact limits of a hard-wooded plant, but speaking generally, it is one with woody stem and somewhat wiry branches, and with fine hairlike roots, which delight in a fibrous, peaty soil mixed with sand. Of such plants a Cape Heath, or, for that matter, our common Heather, may be taken as a type.
There are a good many shrubby subjects which may be said to take an intermediate place, the successful management of which may lead up to the more difficult New Holland and Cape plants. Amongst these easier plants to grow, which are content with good loam instead of peat, may be mentioned the Shrubby Mimulus (M. glutinosus) with pretty salmon-buff blossoms of the Monkey-flower type, of which there is also a noteworthy crimson-red variety.
One of the daintiest of the Calceolarias (C. violacea) may also for convenience sake be placed in this section. It may be grown out of doors ; in fact, in a Dorset-shire garden under the shelter of a wall it grew into a good sized bush, 2 ft. at least in height, and flowered abundantly every season until an unusually severe winter killed it. Neither its foliage nor woody habit, nor its pale-mauve helmet-shaped flowers, are the least suggessive of any ordinary form of Calceolaria, and it is always noticeable in a greenhouse, as it is by no means well known.
Hypericum chinense is another twiggy, low-growing shrub which is almost hardy, and will do well either in a pot or, better still perhaps, in a basket, which would suit its somewhat trailing habit. The large yellow flowers nearly equal in size those of the well-known St. John's-wort (H. calycinum) of our shrubberies, but are much more elegant from a peculiar Catherine-wheel-like twist of petals and stamens, and it may be reckoned a specially fine species of an interesting genus.
The more familiar Polygala dalmaisiana, the purple flowers of which, with quaint little brushes of protruding stamens, is an old favourite, presents no difficulties of culture, needing nothing more than kindly pruning to keep it in shape. Another charming Australian Pea-flower is Swainsonia galegifolia alba, now well known and popular ; it has been found to be hardy against a wall in a sheltered Cornish garden. This may be propagated best by cuttings, as the seed which it produces freely is apt to revert to the purple-flowered type.
All these sub-shrubs are more or less easily grown, and we will now take an example of one that will give more trouble. One of the most gorgeous of Australasian leguminous plants, Clianthus puniceus, is sometimes called the Glory Pea of New Zealand. Those who have seen some of the cottages near Porlock on the Somersetshire coast, with plants in full flower climbing almost to the eaves, will not be inclined to dispute the title.
But it will not grow everywhere out of doors, and in that case must needs be considered a greenhouse shrub. Except for red spider, there is no special difficulty in its culture, but for a long time a finer species still, C. Dampieri, with black blotches on its scarlet flowers-which is not, like the other, an evergreen, semi-climbing shrub, but a herbaceous perennial-puzzled even experienced growers. The secret, however, has been discovered, and a very fine specimen in a large basket hanging in the Himalayan House at Kew attracts much attention as well as admiration during its season. Success depends upon the grafting of the delicate C. Dampieri upon a more robust stock, either C. puniceus or, preferably, upon the nearly allied Colutea arborescens, a perfectly hardy shrub, more common abroad than in English gardens. The result of this grafting is to change the intractable C. Dampieri into a sturdy and easily managed plant, peculiarly well suited to the unheated greenhouse, as in a cool temperature it flowers for a length of time during the early months of the year. An account of a most resourceful method, adopted in some Continental gardens, has been published, and deserves to be quoted.
Seed of both stock and scion are sown in February ; when the cotyledons of the young plants are sufficiently developed to handle, the terminal bud of the stock is removed, and that of C. Dampieri-the scion-is inserted instead. The union is not hard to effect under a bell-glass, but it is, necessarily, a delicate operation. The after-culture is similar to that of other plants of like nature.
The pot or basket in which this fine species is grown must be well drained, however, and more than usual care is needed in watering, as it is stated that the foliage must not be wetted. Probably, also, as in the case of C. puniceus, the less the knife is used the better. This plan of growing C. Dampieri is worth attention, and I give it here, though I have not yet had an opportunity of testing it myself, as any gardener, amateur or otherwise, might be proud of rearing and flowering a good specimen of so grand a plant. It is not impossible that many cases of failure may have been due to over-kindness in the way of coddling, as the other species does so well in the open air in a genial climate.
To come to hard-wooded plants, more strictly speaking, some of the Heaths, such as Erica hyemalis, the later-flowering but fine and distinct E. propendens, and others, Correa bicolor and C. cardinalis, Bauera rubioides, Epacris miniata splendens, Hovea Celsii, Leschenaultia biloba major, Pimelia decussata, and Tremandra verticillata are all suitable subjects, and likely, under careful treatment, to do well in the half-hardy house.
Not long ago, in a somewhat shallow frame under a wall, I saw a batch of strong seedling Heaths, looking like a forest of sturdy young Spruce Firs in miniature, getting ready for a shift into their first pots. This was in the garden of a keen amateur, who had only taken up gardening a year or two previously, and was a bold venture ; but in gardening there is everything to be gained by making such experiments for ourselves. All such plants as the above require a compost of good fibrous peat mixed with sharp sand, and the potting must be very firm-a point which cannot be too strongly urged-as the hair-like fibres prefer a hard soil into which to root.
Above all the soil must never be allowed to become very dry, yet the drainage must be good, as stagnant moisture is equally hurtful. The winter atmosphere of the house must be dry and buoyant, for which reason a very modest amount of warmth is necessary in time of severe frost or, more especially, in continued damp and still weather. Another important point in the treatment of hard-wooded plants is the judicious cutting back of the main shoots immediately after flowering. After this has been done, and as soon as a new growth has fairly started, the plants can be plunged up to the rim of the pots in cocoa-nut fibre or ashes out of doors to rest and ripen their wood for the next season's campaign. An annual re-potting is not necessary, but it should be given when required, just when the new growth has begun. Most of the plants named I have seen doing well out of doors in very sheltered Cornish gardens, therefore there is little fear that they will not do well in a low winter temperature under glass.
Good cold frames or deep pits, however, as well as a conservatory, are indispensable in most gardens where the culture of plants of delicate nature such as these is attempted.
It may be useful to give the cultural details of Hovea Celsii, a very ornamental hard-wooded plant which has long been a favourite, though now not often met with, and of which the clusters of rich purple-blue Pea-shaped flowers are extremely attractive. This plant is more easily raised from seed than from cuttings, and the seedlings begin to make strong growth at once. As soon as they are large enough they should be potted singly in 21-in. pots, and given a shift into a larger size as the roots touch the sides and require more room, care being taken not to allow them to become pot-bound.
Hovea has naturally rather a loose habit of growth, and may be trained either as a standard or as a bush. If the standard form be preferred, the young plant may be allowed to grow as a single stem to a height of x8 in. (or more if desired) before the top is pinched out, when it will break into many shoots. If a bush be wanted, free pinching must be carefully attended to from the first to lay the foundation of a shapely plant.
The soil and treatment otherwise are just the same as that of half-hardy hard-wooded plants in general, for which it will stand as a good object-lesson. It is to the disadvantage of this fine Hovea that it needs a large-sized pot before it comes to flowering size, but it is then very ornamental. Leschenaultia biloba major, with still more brilliant blue flowers, is another hard-wooded plant, better known, which has not the same drawback, as it will flower in a comparatively small pot.
To sum up the requirements of these somewhat exacting plants : A compost of sandy fibrous peat, pots well drained, plants firmly potted, protection given from actual frost, a cool, dry, airy house in winter, careful cutting back after flowering, open-air summer quarters where the pots can be plunged to their rims, and careful watering at all seasons. Where these directions can be carried out the growing of the finest hard-wooded half-hardy plants need present no insuperable difficulty.