Flowers before foliage
With Spring’s arrival, the beds and borders at Heronswood are awash with flowers. Carpets of corydalis, stately tufts of trilliums and hordes of hepaticas are an assault on the senses. But take a moment to glance upwards and you’ll see there are trees that more than match the flamboyant display below. A good example is Magnolia “Iolanthe”, currently blooming beyond the arbor. Like many deciduous magnolias, this popular hybrid produces its flowers before its foliage, a strategy known as hysteranthy. Other Heronswood hysteranths include forsythia, witch hazel, corylopsis, edgeworthia and several azaleas.
Scientists have yet to discover why some deciduous trees and shrubs bloom precociously, but there are a few theories. For species such as hazel (Corylus) and alder (Alnus), which rely on the wind to distribute their pollen, a full canopy of leaves could obstruct the flow of air. Magnolias on the other hand are not wind-pollinated and like many hysteranthous trees, attract insects to pollinate their blooms. A mass of flowers is an arresting sight, especially without the distraction of leaves, perhaps increasing the likelihood of pollination. Bugs are scarce in spring and so, like billboards, spring-flowering trees go all out to win over those early insects.
Magnolia ‘Iolanthe’ is the product of a breeding program initiated in New Zealand. Sheep farmer and plant enthusiast Felix Jury longed to develop magnolias with the large blooms of Magnolia campbellii, but without having to wait (M. campbellii can take up to 25 years to flower for the first time). ‘Iolanthe’ was an unwanted seedling abandoned at the edge of Felix’s vegetable plot, but it produced impressive blooms early on and has now been distributed around the world. The blousy, pale pink petals are wrapped up within fuzzy bud scales, which protect these early blooms from winter weather. Ideal planting partners include many spring-flowering perennials such as hellebores, lungworts and primroses, but avoid digging extensively under magnolias as their shallow, fleshy roots are vulnerable to damage. And in case you’re wondering, Iolanthe is a fairy in the Gilbert and Sullivan operetta of the same name.
– Ross Bayton, Heronswood Taxonomist