Gardening: 'Easy' purple verbena still proves popular
One of the must-have garden plants of recent years, the purple-top verbena gets it common name from the small cushions of purple flowers carried at the top of its tall, rigid stems. These stems can reach two metres tall, though are usually less. When in full flower, the plant carries purple flowers at the tip of every slender stem.
The stems branch almost at right angles to the main stem and, by late summer, the plant creates an open mesh of stiff stems and a haze of rounded purple flowers. The individual flowers are small tubes, purple-pink, gathered together in a round dome.
The botanical name, Verbena bonariensis, is used at least as much as the common name purple-top. The second part of the botanical name refers to Buenos Aires, and the flower is common from Argentina to Brazil. It is a plant of scrubby areas and dry grass land. The tall stems are sent up and flower from June to September.
This plant is very imposing in full flower. Its popularity has come from its natural ability to combine well with grasses. Purple-top is superb with silvery miscanthus and golden oat grass, and rippling ponytail grass, as it lends the right kind of airiness along with purple colour to contrast with the straw-like structure, and silver and golden colours of grasses. This is such an easy plant to raise from seeds, or plants can be bought in garden centres. It is a perennial, making a clump of leaves and stems.
Once established, purple-top sets lots of seeds and self-sows freely, particularly in a gravel area. Unwanted seedlings can be easily taken out before they grow too big. Many of these self-sown seedlings have a knack of turning up in just the right place, often just a crack in paving or a seemingly precarious spot by the side of a path or paved area.
Purple-top is not completely hardy but it survives most ordinary winters. It likes well-drained soil and the roots may rot if the soil is too wet in winter. But, on the other hand, if the soil is too dry, the plant tends to be stunted and not make as many flowers.
Purple top is a magnet for butterflies and bees which visit the flowers for nectar and are encouraged to visit more if the plant is growing in a sheltered spot where the air is warm and the butterflies are not blown about while feeding. Although it is somewhat gangly of growth, purple-top does not need staking or supporting. The stems are stiff and the foliage is not dense and air passes through easily.