(Editor's Note: This article was originally published on April 17, 2008. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
There are many perennial standards in our gardens that are members of the Buttercup Family. Examples include delphinium, monkshood, pasqueflower, columbine, anemone, clematis and hellebores. However, few of these ‘look' like a buttercup. But there are two buttercup relatives that do indeed look like their close cousin; the globeflowers (Trollius spp.) and marsh marigold (Caltha spp.). These two genera are quite closely related and have similar cultural requirements. Marsh marigolds bloom in mid-spring while globeflowers bloom from late spring-early summer. Both are found in cool temperate regions, usually growing in sunny to partly shaded damp meadows or streamsides, often in quite heavy, organic-rich soil. Hence, these are the conditions we must strive to duplicate in our gardens if we wish to grow these glorified buttercups. Perhaps the best area to grow these would be a bog garden or on the fringes of a water feature. However, we don't all have the luxury of such specialty garden features. Not to worry, they can also be grown in the standard perennial border as long as the soil is reasonable moist. On the whole, globeflowers will tolerate slightly drier conditions than marsh marigolds.
There are about 30 species of globeflower (Trollius), most being distributed in eastern Asia.. In our gardens, we grow only a few of these and some hybrids. The most important species are T. europaeus, T. asiaticus, T. chinensis and T. ledebourii along with hybrids derived form these. The European globeflower, T. europaeus is widely distributed throughout Europe, extending north of the Arctic circle. As such, it is one of the hardiest globeflowers, being rated for zone 3. Plants grow to about 1 m with palmate, deeply divided leaves. The flowers are lemon-yellow, about 3.5-5 cm in diameter with 10-20 petaloid sepals (as a rule, the buttercup family ‘flowers' are composed of sepals which are modified to look like petals; their real petals are often very reduced and insignificant). The actual species is rare in our gardens but the cultivar ‘Superbus' (shown left) is reasonably common. That cultivar is more compact (to 60 cm) with fuller flowers that are pale lemon-yellow.
Much confusion surrounds the identification of the east Asian species T. chinensis vs. T. ledebourii. Suffice it to say, the two are very similar. Both reach about 1 m with deep orange, 3.5-5 cm diameter flowers with 5-10 sepals. The flowers are not as ‘full' as T. europaeus or many of the hybrids, but the thickened, upright, stamen-like petals make these two species unmistakable. It is the latest-blooming globeflower. Most popular is the hybrid ‘Golden Queen' (introductory photo) which may well be a hybrid between the two species. These are hardy to zone 4.
Most of our garden hybrid globeflowers have quite full flowers (15-20 sepals) on bushier, more compact plants than the species. Popular hybrids include ‘Alabaster' (pale cream-yellow), ‘Cheddar' (I can't tell it from ‘Alabaster'), ‘Goldquelle' (bright yellow), ‘Orange Princess' (medium orange, shown left), ‘Earliest of All' (golden yellow), ‘Lemon Queen' (very similar to ‘Superbus' but taller) and ‘Fire Globe' (deep orange). Rated for zone 3-4.
For the rock garden there are two main species; T. acaulis and T. pumilus, both Himalayan species. The two are quite similar but T. pumilus has 2-3.5 cm flowers and basal leaves while T. acaulis (shown right) has 3.5-5 cm flowers without basal leaves. Both have single, 5-sepalled yellow flowers on plants 15-25 cm tall. They are rated for zone 5, but can survive zone 4 if there is reliable snow cover.
There are only 10 species of marsh marigold (Caltha) and really, only one is a popular garden plant; the common marsh marigold, C. palustris. Marsh marigolds generally have shiny, rounded, somewhat fleshy leaves and single ‘buttercup-like' flowers with 5-9 sepals that are either white or yellow. Contrary to popular belief, marsh marigolds do not have to be grown as a shallow aquatic plant. I have grown them for years in my regular perennial border. However, they do require a reasonably moist soil, so I do water them regularly. Certainly, the ‘wild' species is more difficult in a regular garden setting than its varieties. The straight species is variable in size from 45-80 cm. The most important ornamental variety is ‘Flore-pleno' or ‘Multiplex' (shown right) which has fully double, pom-pom like flowers on a more compact plant. The cultivar ‘Alba' has deeper green leaves and bright white flowers with contrasting yellow stamens. These two are more adaptable to garden cultivation. For moist spots in a rock garden, you can grow the Rocky Mountain species C. leptosepala (aka C. biflora or C. howellii) which grows 20-30 cm with white blooms. The above Caltha species are rated to zone 3.
Above are pictures of Caltha palustris 'Alba' and C. leptosepala
Globeflowers and in particular, marsh marigold, do have one main drawback in the garden. If the weather becomes too hot or the ground too dry, they will go summer-dormant which means you may have a gap in the border for several months, so plan accordingly. I plan ahead by planting some annuals near them to help hide the late summer gap.