It is true that nothing else can quite take the place of chrysanthemums in greenhouse decoration. They are so universally grown, however, and it is so easy to get information on all points with regard to them, that it will be more profitable to inquire what other flowering plants are attainable from Michaelmas to the end of the year.
Naturally, we think first of the few late-blooming perennials which, though quite hardy, are likely out of doors to have their flowers either crippled or wholly destroyed by early frosts. One such, often grown in pots on this account for the greenhouse, is Stokesia cyanea, a fine composite, with blue Thistle-like flowers.
There are two varieties-a fact which has only recently been made known-and as one of these is summer-flowering, care should be taken to get the right sort for late work. Aster grandiflorus, the latest of the Michaelmas Daisies, is sometimes treated in the same way, as it seldom perfects its large blue flowers in the open border. Senecio pulcher is a good late-blooming Groundsel, with red-purple flowers, which may be put into the same list. It is interesting to grow it from inch-long root-cuttings in early autumn, like Seakale, thus securing fresh plants every year, and the best effect is made when several plants occupy a broad, deep pan to form a clump. The colour of the flowers, unfortunately, is one that contrasts badly with most others, which is a drawback.
A very good low-growing plant belonging to the same genus, Senecio Kempferi, may be mentioned here, though it is somewhat more tender. It has broad, handsome foliage, splashed with white and a touch of pink, and is worth growing both for its leaves and flowers. It bears a loose cluster of large yellow Daisy-like flowers, and is more often seen in Belgium and elsewhere on the Continent as a window plant than with us. This is not to be confused with Farfugium grande, with round yellow spots on its green Coltsfoot-like leaves, which is, perhaps, a greater favourite with English folk than it need be.
Chrysanthemum serotinum, better known amongst herbaceous perennials as Pyrethrum uliginosum, rears its great height and holds up its flowers high above our heads in the autumn garden, unless the precaution is taken of heading down the plants in early June. These tops may be put in as cuttings and make excellent little pot plants, proving very useful in the greenhouse during October and November. The Winter Cherry, Physalis Franchetti, is striking and handsome for late autumn when grown with several stems and hung with its vivid orange-scarlet capsules. It is much finer in every way than the old P. Alkekengi. The first frost makes the leaves drop when the plant is out of doors, but with the protection of glass we get foliage with the brilliant lanterns, which is a great gain.
Another hardy Japanese perennial-Tricyrtis hirta-which is, strictly speaking, a miniature Lily, with a short, creeping root-stock, makes an admirable late cold greenhouse plant. Its pretty mauve-white flowers, spotted with lilac or purple, are very Orchid-like in their effect, and are borne pretty freely.
Carnations of the self-coloured Grenadin type, which are chiefly white and scarlet of various shades, are invaluable for autumn flowering. If the object is to ensure really good flowers it is a good plan in the first instance to raise a batch of seedlings from reliable seed of the best strain, which should be allowed to flower the first season in the open ground.
Many variations will occur amongst them, and a strict selection of the finest must be made for future stock. Any tendency to throw up flower-stems in the spring must be kept in check, and layers should be laid early in the season, before midsummer if possible.
When thoroughly rooted, which will he in about six or eight weeks from the time of layering, they should be transferred to 5-in. pots, and it must be borne in mind that Carnations, of all plants, like very firm potting to ensure good flowering. If all goes well flower-stems will soon begin to appear, and a cold frame will be sufficient to bring them on until they are ready for the greenhouse.
For hanging-baskets or pans raised to a position near the eye, a creeping Himalayan perennial, familiarly known as the Shamrock Pea (Parochetus communis), which flowers naturally in October and November, is extremely pretty, both in its twin Pea-flowers of pale stone-blue and its large trifoliate leaves. It is also more satisfactory to flower under glass than out of doors, even on the most sheltered rockery. For the same purpose two Italian Bell-flowers, Campanula fragilis and C. isophylla alba, are invaluable, the latter being the more easy of the two to grow into a fine specimen.
A little early pinching-back of the shoots will help to retard their flowers till late autumn, when they are very welcome. Though these are both natives of sunny Italy, they prefer partial shade when under glass. A fine blue variety, C. isophylla Mayi, named after its raiser, has recently been introduced.
So far, mostly quite hardy plants have been under consideration, but there are a good many half-hardy perennials which may be used, with a little careful preparation beforehand, for the autumn greenhouse.
Two or three dwarf species-not varieties-of Dahlia, for example, come in very well to fill up a gap at this late season. D. gracilis, a slender-growing Mexican plant, with bright scarlet single flowers and finely cut leaves, is good and showy, only care must be taken to secure the true species, and not some coarse-growing seedling masquerading under the name. D. glabrata (syn. D. Merckii) has smaller lilac or white flowers, but produced very freely ; while the Black Dahlia, so-called (which is not really a Dahlia at all, but Cosmos diversifolius), makes a good foil with its dark brown, velvety petals. These can be raised from seed, and answer best if they are grown in pots plunged out of doors during the summer, and all the strength thrown into the growth by the removal of all buds until the plants are wanted to flower.
Arctotis arborescens, a very beautiful, but rather tender, perennial, often used for summer bedding, comes under this class. It is somewhat bushy in habit, and likes plenty of room, but it is well worth taking any pains to get its large creamy-white flowers in autumn.
These are tinged with pink on the under-side of the petals, and the fine grey-green foliage sets them off to great advantage. How true it is that no greenery goes better with any flower than its own leaves. Another species, A. aureola, has glowing orange flowers, which it produces till quite the end of the year out of doors in the Isles of Scilly, and would probably answer as well as the larger-growing A. arborescens. Alas ! they have one fault, they close in dull weather.
Paris Daisies, both white and yellow, grown from spring-struck cuttings, make delightful autumn plants when plunged out of doors during the summer, and the points of the shoots carefully pinched out to make them bushy. There is something so innately cheery about them that, common as they are, they may not be left out of our year-end programme.
Several of the hardier Salvias, treated in the same way, make fine and useful plants. They are so quick-growing, as a rule, that after the cutting stage is passed they require several shifts during the season, until finally they reach a 9-in. pot, in which size they should flower well.
Severe pinching is also necessary to make them compact, but in any case they take up more room than most plants. For a strictly cold greenhouse it is better to be content with such species as S. Pitcheri (syn. S. azurea gra ndiflora), S. coccinea superba, S. Hians, purple with spotted lip, and S. patens, well known, with deep blue flowers, of which there is also a white form, rather than the more tender species.
In a good season, however, and with the temporary help, on occasion, of a heat radiator, S. splendens, with its brilliant scarlet spikes, S. gesnermfolia, and S. rutilans, but with Pineapple scented foliage, may be successfully grown, though they need a genial temperature of at least 50° to develop their flowers satisfactorily. The cultural treatment of both hardier and more tender species during the summer is identical.
The subject of retarding flowering plants by refrigeration, which is coming so much into vogue, can hardly be passed over without some reference here. It is now quite possible to procure many different kinds-perennials (such as Astilbe japonica, better known as Spirxa), bulbs, represented by several species of Lily, and even hardy deciduous shrubs, like Azalea mollis-ready prepared to flower in the autumn greenhouse. These will, probably, require special care to bring them to perfection after the severe ordeal to which they have been subjected. But the amateur who loves his plants, and desires to know more of the unstinted variety which the garden of the world offers to the seeker, may do better than to hark back to spring when so great a wealth of autumn flower is within his reach. There is more show of reason for helping autumn and spring to clasp hands over the sleeping form of winter.