We admire their vibrant colours in winter, when little else in the garden is bright, and their frilly, bouquet-like form delights us – so why aren’t more of us growing this chilly season spectacle in our own gardens? We’re talking coloured (more officially known as ‘ornamental’) kale – those gob-smackingly-gorgeous, flauntingly-fabulous brassicas, most often spotted growing en masse in parks and gardens. Many of the colourful ornamental kales we see growing are F1 hybrids – plants specially bred to develop the bright purple, pink, rose, ivory-white, and greens we adore in these hardy plants. Breeding has also exaggerated the broad flatness and deep crinkles of their colourful foliage.
While ornamental kale will technically grow in any part of the country, cool spring and chilly autumn-winter seasons are when they’re at their best. This is when colder night time temperatures signal the plants to produce anthocyanin – pigments which help protect the plants against chill while at the same time deepening the colours in the leaves.
Despite the attractiveness of ornamental kale, it’s not actually a flower we’re seeing when we admire their display. Rather, ornamental kale is a ‘biennial’ plant, which means it takes two years for it to develop a flower and produce seed. So the display we enjoy is actually just the first stage in the brassica’s life-cycle. From those colourful leaves will eventually sprout long stems on which are born clusters of bright yellow flowers – and while these blooms may appear dramatic, they’re not the look gardeners are after. In fact, in parks and garden situations, the ornamental kale will be ousted long before its flowering stage occurs.
Back to the question of why, when we enjoy it so much, we don’t often grow ornamental kale in our own gardens: the answer could be, while ornamental kale is relatively easy to care for, it is still susceptible to the same bugs and disease as other brassica. In New Zealand, this includes the dreaded cabbage white butterfly. These butterfly lay their eggs on brassica leaves over the summer months, resulting in the arrival of numerous leaf and stem-chewing green caterpillar that can defoliate a kale in days. While we may be quite happy to net our vegetable gardens against the arrival of white butterfly, an ornamental bed looks considerably less acceptable when covered in the same material.
There is, however, one way to mitigate the damage to ornamental kale from white butterfly while still maintaining the attractiveness of our flower garden. The secret lies in growing the ornamental kale seedlings in pots large enough to accommodate root growth until early winter, by which time (in most regions) the white butterflies have stopped flying. Out of view, the pots can remain covered in net for as long as necessary. Then, once summer annuals are spent and have been removed from the ornamental bed, nutrition can be added to the soil, and the kale seedlings can be transplanted out.
Ornamental kales make a delightful display on their own, but to maximise their impact, they can be interplanted with hardy winter-flowering annuals such as fairy primrose, pansies, snapdragons, Iceland poppies, or polyanthus. If you have perennial winter flowering plants in your garden, such as Erica or winter roses, consider tucking ornamental kale in between to compliment the colours.
Ornamental kales are a fascinating, joyful addition to the winter garden. Whether you plant them on mass, in rows along the edge of your drive, or as a display in balcony pots, they are sure to draw attention – especially from children!
