These tender perennials, are usually treated as annuals and add colour and fragrance to sunny borders everywhere
I creep into the world of verbenas with great trepidation. I try to clear up confusion in any plant I post about but I have some pressing work that needs doing and I think I would need to spend a lot of research time getting to the bottom of the verbena naming mess.
So, with apologies, this might be confusing! There are lots of verbenas (250 species), largely native to the Americas and some to Asia but, with the Europe-centric classical history I have grown up with, the most famous is V. officinalis, commonly known as vervain.
After that, things get messy. The most popular perennial, at present, is V. bonariensis, the tall, see-through, seemingly leafless plant with dense clusters of tiny lilac flowers. It is native to Buenos Aires – hence the botanical name. I am also very fond of V. hastata, which is a shortlived perennial about 60cm high which I have grown in both pink and purple and which flowers the first year from seed. Then there is V. rigida, which is usually grown as an annual, with an upright habit and lots of tiny purple flowers – very popular in bedding. Verbena tenuisecta has finely divided leaves and is usually purple but can be other colours and then there is V. officinalis var. grandiflora ‘Bampton’, a strange plant with small, purple leaves and microscopic purple flowers, grown primarily for its tousled foliage.
All have long-tubed flowers in clusters, with five, spreading petals and often a contrasting colour at the mouth of the bloom. The flowers are either held in domed clusters with the outer, lower flowers opening first, or in long spikes. The calyx is often ribbed and covered in rough, glandular hairs.
I am not sure what to call the bedding verbenas. I thought they were derived from V. peruviana. I am sure we planted something called V. phlogopappa when I was a student. Perhaps these should be called V. x hybrida. I am at a loss. And then there are glandularias. These look just like verbenas to me, I have seen them growing wild in the S.W. USA and I really don’t know what makes a glandularia and what makes a verbena!
To make things worse, most of the verbena plants you buy in spring are vegetatively propagated and not raised from seed. And they have trademarked names like Superbenas. Each breeding house has introduced its own series with varying traits such as improved resistance to disease, creeping or trailing habit and unique colours.
Most verbenas, either from cuttings or seed, are trailing plants, wider than high, and flower for months, especially if deadheaded. Many, especially those with pink, purple and white flowers, are fragrant. The flowers are very attractive to butterflies and moths as well as bees. Seed-raised kinds tend to get exhausted if allowed to set seeds and frequently get powdery mildew. Keeping plants moist and well fed will help to avoid this but, because drying out is so common in hanging baskets I think they are better suited to containers rather than baskets.
If growing from seed, add some extra drainage to the compost – verbenas hate wet compost when small. Water them very carefully at first but once they have several stems and a dozen leaves they are much easier to look after. You can pinch out the growing tips if you like, which will delay flowering but encourage bushiness. Flowering will be best in full sun but a few hours of shade is tolerated.