Michaelmas daisies

Derrick Rooney1

Aster is a genus of flowering summers with regular rainfall, and in the daisy family, (or irrigation as well. They do not thrive Compositae as the family is also in hot, dry weather. Unless they are known). The genus once contained divided at least every second year nearly 600 in Eurasia and and only the youngest pieces are North America, but during the 1990s replanted in fresh soil well enriched American taxonomists segregated the with organic matter, New York asters North American species to a series of are martyrs to powdery mildew, other related genera. Fig. 1 novi-belgii ‘Gayborder Blue’. which stunts their growth and inhibits flowering. Some cultivars are resistant All but one of the 180 or so species angliae. The former was responsible to mildew but have rhizomatous remaining in Aster are restricted to for many famous cultivars, including roots that quickly spread into Eurasia. A North American species, the post-World War II A. ‘Peace’, extensive clumps, smothering smaller Aster alpinus subsp. vierhapperi, is A. ‘Prosperity’, and A. ‘Plenty’. These neighbouring plants. New England the exception. are large-flowered cultivars which asters are apparently immune to The European Michaelmas daisy, were popular and widely available mildew and have compact, non- Aster amellus, once a very popular from nurseries in the 1950s and spreading rootstocks that need not border but no longer seen in 1960s until garden fashion swung be divided at less than five-year nurseries in New Zealand, is the type away from the classic massed colours intervals, but are even less tolerant of species of the genus, as well as of the of herbaceous borders to mixed dry summer weather. family Asteraceae. The New World borders featuring shrubs and roses Fortunately for dry-climate gardeners, species are now reclassified in about mingled with herbaceous plants, and this large family of Michaelmas 10 genera, of which species from only more emphasis on foliage than on daisies includes small-flowered one, Symphyotrichum, is in general flowers. The addition of A. dumosus but attractive species that have cultivation in this country. to the mixture enabled breeders in the United States, Britain, and Europe not played a role in the major Symphyotrichum embraces the to raise “dwarf” cultivars that grew development of the cultivars but have horticulturally significant group of no more than 50 cm tall and thus the virtue of immunity to mildew and species from which Michaelmas needed no staking but had full-sized the ability to pass this trait on to their daisies were developed. However, flowers. New York asters typically offspring. Among the best of these all the species in the Michaelmas have smooth green leaves, often are Aster cordifolius, A. ericoides, daisy group are still referred to flushed beetroot red on the underside, and A. lateriflorus. All three have in the nursery trade as “asters” and grow from 1 m to 1.4 m tall. been grown in New Zealand for many and will continue to be so called Flower colours range from white years without gaining widespread in the immediate or even in the through lilac pinks and lavender to popularity, either because they have distant future. As has previously purple or garnet. There are no true small flowers, because they have happened with Chrysanthemum and reds in Michaelmas daisy flowers. semi-woody rootstocks and can Dendranthema, the invalid but familiar True reds are also lacking in the only be propagated, with difficulty, name is likely to be conserved for New England asters, which range from early-season basal cuttings, or common usage. For this reason I will from white through shades of pink because they have never been well continue to use the name aster in this to amethyst and royal purple. Well- publicised. None is drought proof, but article. known pink-flowered cultivars that the latter two are tolerant of long, dry spells of summer weather. Both have In the “new” genus, Symphyotrichum, are still sometimes available include compact, semi-woody root systems more than 80 species, all North A. novae-angliae ‘Barr’s Pink’ and that can be difficult to divide, and American, have been named A. ‘Harrington’s Pink’. New England both have branched inflorescences, in several different sections or asters generally grow to about 1.5 m, with the small flowers arising from subgenera, but some of these are and have grey-green leaves. short, twiggy, side branches on self- almost certainly synonymous and only For gardens in areas where summers supporting main stems. a handful is of horticultural interest. are either hot or dry or both, the The heath aster, A. ericoides, has Just three species have dominated New York and New England asters small linear leaves and either lilac the development of modern have serious drawbacks. In their pink or white flowers, opening flat Michaelmas daisies: the New York natural habitat both are plants of on branchlets that arise at about a aster, Aster novi-belgii (Fig. 1), the damp meadows, bogsides, ditches, 45-degree angle from the main stem. dwarf aster, A. dumosus, which is and streamsides. They sometimes Aster ericoides ‘Monte Cassino’, with treated as a subspecies or variety of grow in damp places on woodland tiny white flowers, is an excellent, New York aster by some taxonomists, margins but do not occur in deep free-flowering cultivar. and the New England aster, A. novae- shade. They grow best in cool

1 PO Box 43, Hororata, Canterbury, New Zealand; [email protected]

12 New Zealand Garden Journal, 2012, Vol. 15(2) Fig. 2 Aster lateriflorus var. Fig. 3 Aster ‘Hi-Jinks’. Fig. 4 Aster ‘Lo-Jinks’. Fig. 5 Aster ‘Mini-Jinks’. lateriflorus. Aster lateriflorus, usually seen in and in early autumn is smothered by to a chain of hardware stores. More gardens in its variety lateriflorus a profusion of flowers, each about the recently it has been catalogued by (Fig. 2), is known as the calico aster. size of a dollar coin. This plant, too, a well-known mail-order nursery, This distinctive plant has so many has purple disk florets and white ray unfortunately misspelt as A. ‘Lo-Jinx’. very small flowers that sheer numbers florets, but instead of remaining white None of the three has produced any compensate for lack of individual size. the ray florets gradually turn rosy viable seed in my garden, but the one It too has self-supporting main stems, purple as they age, giving a plant in larger-flowered plant that I kept is fertile from which the flowering branchlets full flower a patchwork look. I named and in the last few years has produced sprout at close to right angles. The them Aster ‘Hi-Jinks’ (Fig. 3) and a number of seedlings more closely tiny, reflexed ray florets are white and A. ‘Lo-Jinks’ (Fig. 4) respectively. Both resembling the calico aster. So far, the disk florets are rosy purple. While appear to be sterile. however, none of these has been worth calico aster is not completely drought A year later a repeat of the cross keeping and naming, although I have proof, it requires a drier site than yielded a second apparently sterile selected a couple for further trials. either the New York or New England small plant similar to A. ‘Lo-Jinks’ but asters. Aster cordifolius also has small flowers with slightly smaller ray florets that on angled branchlets arising from a This ability to tolerate dry summers, remain white as they age. I kept this central stem, but its main distinguishing coupled with the resistance to mildew, plant too, and now call it A. ‘Mini-Jinks’ feature is the cordate basal leaves, prompted me in the early 1990s (Fig. 5). Several plants from the same dark green on the upper side and to cross calico aster with a “dwarf” batch had larger lilac pink or white beetroot red underneath. Aster Michaelmas daisy, A. ‘Peter Harrison’, flowers and more closely resembled cordifolius ‘Silver Spray’, which was in the hope of producing larger- the A. dumosus parent. These grew promoted in the 1980s as a “flower flowered plants able to stay healthy about 40 cm tall, with flowers about arranger’s plant”, is the best-known while withstanding the dry summer 2.5 cm to 3 cm across. These were cultivar, but the plant I grew under heat that frequently occurs in my very floriferous. Initially I thought they this name did not appear to differ garden in inland Canterbury. A. ‘Peter showed considerable promise, but significantly from ordinary seedlings. Harrison’ was an English cultivar, not within two years I had discarded all The plant is fertile but in my garden its connected to the Harrison family who but one of them because they proved seedlings have invariably resembled dominated the perennial and bulb to be too fertile, producing numerous their parent, so it presumably rarely trade in New Zealand from the 1950s unwanted inferior seedlings. hybridises spontaneously with other to the 1980s. It had relatively large The experiment came to an abrupt Michaelmas daisy species. soft pink semi-double flowers and halt when A. ‘Peter Harrison’ died in grew only about 35 cm tall. I used it as Like the New York asters, A. cordifolius an abnormally dry summer and I was the pollen parent. prefers heavy soil and abundant unable to find a replacement for it. summer moisture, but it appears The resultant batch of seedlings failed Sixteen years on, I still grow the three to be immune to mildew. Its woody to produce large-flowered plants. Most named “Jinks” plants. All three have rootstock cannot successfully be of them resembled the seed parent, continued to be hardy, floriferous, and divided. The only ready means of calico aster, but without the distinctive tolerant of adverse conditions in both vegetative propagation is by basal horizontal branching. However, I summer and winter. I consider A. ‘Lo- cuttings of the young shoots in late selected two before discarding the Jinks’ to be the best of them. It has spring or early summer. The strike rate rest. One grows between 70 cm and proved its hardiness and adaptability is close to 100 per cent if the cuttings a metre tall and has flowers about by growing equally well without any are given bottom heat and kept in a 1.5 cm across, with plum purple disk special attention in a friend’s garden humid atmosphere until they are well florets and ray florets that open flat close to sea level, in my own garden rooted, but home gardeners who have instead of reflexing. The ray florets at 200 m asl, and my daughter’s no special propagating facilities can are white but the disk florets are so garden at 695 m asl in the Lake Heron strike them in a cold frame, albeit with strongly coloured that the general Basin. Some years ago I supplied a lower success rate. Unlike most effect from a distance is of a mass of propagating material of A. ‘Lo-Jinks’ other Michaelmas daisy species, light rosy pink. The other selection to a large wholesale nursery, which A. cordifolius does not need, and does was a small, densely tufted plant that subsequently sold about 2000 plants not like, regular lifting and replanting. grows only about 20 cm to 25 cm tall

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