This section is from the book "Beautiful Gardens - How To Make Them And Maintain Them", by Walter P. Wright. Also available from Amazon: Beautiful Gardens: How To Make And Maintain Them.
Considered as garden plants, Begonias and Dahlias have something in common, inasmuch as both are tuberous and late bloomers, but with tender growth that is destroyed by frost in autumn. The cultural routine with both runs on parallel lines, but in habit they are far apart.
The tuberous Begonia developed enormously during the closing years of the nineteenth century. The cross fertilisers gave us a splendid series of both single and double varieties, with good habit, large flowers, and a brilliant range of colours. The result was that Begonias grew rapidly in favour, both as greenhouse and garden plants. Their progress as bedding flowers has not been altogether uninterrupted, for in dry seasons they have been found ineffective on shallow, hot soils, making poor growth, and producing inferior flowers. This has resulted in setbacks in some districts. On moist, clay soils the tuberous Begonias are always good, and so far from a dry season proving inimical to them they revel in it, making strong growth and bearing the finest of flowers. The author's greatest Begonia treat was in the dry summer of 1906, and fortunately it was prolonged owing to the mild autumn, which enabled the plants to maintain their beauty until the middle of November. It is as late summer and autumn flowers that Begonias are so valuable, and they should be at their best from the end of August to the middle of October.
For bedding purposes the best way of getting a suitable stock is to sow seeds of a good strain in heat in January, select the best varieties that result, and increase them by cuttings or by dividing the tubers. Named varieties may, of course, be purchased, but this is a somewhat expensive way of getting up stock. The seed is very small indeed, and should be carefully dusted over a fine surface, settled with a few particles of silver sand, and covered with damp moss, which must be removed when the seedlings appear. If grown on briskly, and planted in June, they will advance sufficiently to show their character the first year, although they will not be at their best until the second season.
The tubers, lifted in October or November, keep well in a cool outhouse, if safe from frost. They are best stored in Pine sawdust, as this generally keeps mice from them. Directly they show signs of growth in spring they may be packed in leaf mould in shallow boxes, and put into a frame. This will ensure sturdy growth, and the plants can be put out with the leaf mould clinging to them when the proper time comes, so that they sustain no check. Very little heat is needed to bring the plants on for bedding; that of a mild hotbed of leaves and manure suffices, indeed, they will do in a cold frame if protected in frosty weather. The more heat that is given the greater the necessity for care in hardening off before the plants are put out.
The fibrous-rooted section comprises several excellent bedding Begonias, dwarf in habit, and brilliant in colour. They can be raised from seed, and subsequently increased by cuttings in heat in spring or autumn similarly to the tuberous. Reading Snowflake, white; and semperflorens rubra, otherwise known as Crimson Gem and Vernon, are two of the best varieties for the purpose in the fibrous-rooted section.
Where Begonias are being grown in light, hungry soil deep working should be practised, and a heavy dressing of cow manure incorporated. Further, the surface should be mulched with short manure. Good soakings of water will help the plants.
It may be added that those who like a quicker effect than they can obtain from seedlings, and who yet cannot afford to buy named varieties in sufficient quantity, can often procure very good bargains in the way of sets of tubers of selected bedding sorts, unnamed, in spring.
The Dahlia is by no means a modern flower in the same sense as the tuberous Begonia, inasmuch as the florists of fifty years ago had varieties (of the Show and Fancy sections, at least) as good as any we have to-day. All the same, garden Dahlias have been immensely improved during recent years. The best of the Cactus and Pompon varieties are vastly superior garden plants to the treasures of the old florists, and it is to these sections that we must go in search of garden material. Fortunately, it is not only beautiful but cheap. It is true that novelties are dear in their first year, but propagation is so rapid, and competition among growers so keen, that high prices do not last long.
Valuable as the Cactus Dahlias are for the garden, there is still room for great improvement in one particular direction - namely, in the flower stems. In the majority of the varieties the flowers are too heavy for the stems to hold upright, with the result that much of the effect which the plants should produce is lost. It is to be hoped that flower gardeners will press the criticism on this point, with a view to convincing raisers that stiff, strong flower stems are equally as important as handsome flowers. At the same time, something can be done by the cultivator.
If he restricts the main branches of his garden Dahlias to half a dozen (increased to eight in the case of Pompons), he will get much more effective plants than if he allows them to grow unchecked, and become crowded with foliage, in which the flowers are often half buried.
That Dahlias love a deep, rich, fertile soil is well known. Mere manuring is not enough - the plants must have a deep root run to thrive. The ground should therefore be dug two spades deep, and in the process a coat of well-decayed manure incorporated. If there is any choice, select a heavy rather than a light soil, as it will hold more moisture, which Dahlias love.
Although plants may be raised from seed it is hardly worth while in view of the fact that excellent varieties can be bought for a few pence each. These may be ordered in March or April, to make sure of them, and planted at the end of May. Sturdy plants 7 or 8 inches high, turned out of small pots, will be best. They will form stools of tubers by October, if they have done well; and if they are lifted, dried, and stored in a cool, dry shed or cellar, they will throw up plenty of shoots suitable for cuttings in spring. Annual propagation is an advantage. Of course, old stools may be replanted, but as a rule they flower too early, and do not make such fine plants as young stuff. In preference to planting old stools, divide them, and plant the separate tubers. Cottagers frequently get good plants by following this plan.
Strong stakes must be used for the main growth, and if the side branches can be neatly tied out to shorter ones finer plants will be got. It will be well to follow the time-honoured plan of inverting a small flower pot bedded with hay on each stake, to serve as a trap for earwigs, which must be searched for in the morning.