Monday 18 December 2017

Striking a blue note against autumn golds

SOMETIMES plants can unexpectedly reveal themselves in a different light and give a fresh insight into how they can be used in the garden. The very severe frost of recent winters has revealed interesting aspects of many plants.

One such is the lovely Mexican petunia or Strobilanthes atropurpureus. While the common name Mexican petunia exists, it is not really used and the botanical name is much more likely to be heard. However, a botanical name like this militates against a plant becoming popular in gardens.

This is a plant that should be hugely more popular than it is. It is occasionally seen in old gardens and in the gardens of people who know its value, but it is rarely seen for sale, though it is eminently worth seeking out.

The reason for the value of this perennial flower is its ability to flower in autumn when its blue colour is especially valuable as a contrast to the colours of the season. It has hooded flowers, shaped like a tuba, of intense but bright blue-violet, vibrant, later turning purple-blue. These flowers make an eye-catching contrast with the yellow and orange tones of autumn foliage.

The plant is normally about waist-high, which is fine in larger gardens but a bit tall for most small gardens. However, the severe frost knocked the plant back and it did not grow as tall this year.

This observation indicates that the plant could be clipped over in spring to shorten the following growth and give a shorter plant. Clipping would probably delay flowering too, which is a benefit because its late flowering is its value.

While a common name is Mexican petunia, it is neither a petunia nor from Mexico. It is related to acanthus, a plant with large leaves and tall foxglove-like flowers, and it is from the Himalayan region. It looks more like a salvia than acanthus, with pointed nettle-like leaves. The foliage is rough to touch and shows prominent leaf veins.

The overall shape of the plant is also nettle-like and the flowers are carried at the top of the stems. The blue flowers are carried on short stalks and open in succession over many weeks in late summer and well into autumn.

It is a robust plant, able to resist weeds and the competition of other plants because the clump of stems is quite dense. Also it spreads with underground rhizomes, but it is not a fast spreader or very invasive. It likes reasonably good soil, well-drained, and a sunny position for maximum flowering. It would be best used in a few clumps, each to pick up the colour of the other and carry the blue note through the garden.

Sunday Independent

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