This section is from the book "The Standard Cyclopedia Of Horticulture Vol2", by L. H. Bailey. See also: Western Garden Book: More than 8,000 Plants - The Right Plants for Your Climate - Tips from Western Garden Experts.
The kinds most suitable for out-of-door culture are those making abundance of rhizomes or underground stems, which withstand the winter and furnish the new growths for the successive years. The Pompons are more hardy than the large-flowering sorts, and, as hardiness is of vital importance to those interested in this subject, especially north of the Ohio River, it should be fully considered in selecting for this purpose. It is more practicable to choose varieties which perfect their flowers early, during August, September and October when grown in the northern states, as the buds are less likely to 'be injured while in a soft growing state by frost. In the South many of the later varieties will live over and be satisfactory, owing to the continuance of mild weather. In the past few years, some improvements in this section have been attained, many of which are the results of crosses between the Pompons and the large-flowering Japanese, in which the progeny have combined the hardiness and dwarf habit of the former with the larger and more irregular-formed flowers of the latter, producing aster-like flowers rather than the symmetrical form of the pompons. All of the types may be successfully grown out-of-doors if provision is made to protect the bud, blooms and roots from severe frost.
A temporary covering of cloth or sash in early autumn will protect the blooms, but the roots will require artificial heat or should be removed to the greenhouse or frame where the temperature can be maintained a few degrees above freezing. In growing exhibition blooms out-of-doors, all the important details, such as watering, airing, disbudding, feeding, staking and tying, must be complied with, if the grower expects to be rewarded for his efforts.
The oldest of the outdoor types are the Pompons, which produce from forty to one hundred buttons an inch or two across, with short and regular rays. Such plants can be left outdoors all winter.
Since the large-flowering or Japanese types have come in, numberless attempts have been made to grow them outdoors, but with poor results. The greenhouse varieties are not so hardy. In the North they are likely to be killed by the winter. Their flowers usually lack in size, depth and symmetry, largely because there are more of them on a plant than a florist allows for his best blooms, but chiefly because they do not have so much care in general as is given to plants under glass, where space is precious. For the very best results, chrysanthemums must be flowered under glass, and they need the greatest care and forethought practically all the year round. Half-way measures are unsatisfactory. Thus it happens that the Japanese varieties are usually unsatisfactory out-of-doors, and the Pompons are chosen by those who can give very little care to plants and would rather have many small flowers than a few large ones. This also partly explains why no two dealers recommend anything like the same list of Japanese varieties for outdoor culture. Nevertheless, it is possible to grow excellent flowers 4 and 5 or even 6 inches across outdoors, but it requires staking, disbudding, and some kind of temporary protection, as of a tent or glass, during frosty weather.
Fig. 957 shows a cheap and simple structure of coldframe sashes resting on a temporary framework. In severe weather a canvas curtain can be dropped in front, and the window of a warm cellar in the rear opened to temper the air. For general outdoor culture, however, when no special care is given to the plants, the Japanese kinds are usually less satisfactory than the Pompons. These Pompons are a much-neglected class since the rise of the large-flowered Japanese kinds, but they are unlike anything else in our garden flora. Their vivid and sometimes too artificial colors harmonize with nothing else at Thanksgiving time, and they are so strong and commanding that they should have a place by themselves. It is not uncommon for the flowers to be in good condition even after several light falls of snow, and they may be considered the most resistant to frost of any garden herbs. In fact, their peculiar merit is blooming after the landscape is completely desolated by successive frosts. The flowers are not ruined until their petals are wet and then frozen stiff. They are essentially for mass effects of color, and great size is not to be expected. Masses of brown and masses of yellow, side by side, make rich combinations.
The whole tribe of crimsons, amaranths, pinks, and the like, should be kept by themselves, because their colors are variable and because they make a violent contrast with yellow, which few persons can find agreeable.
Fig. 957. Suggestion for protecting chrysanthemums that are to bloom outdoors.