Dazzling flowers in a multitude of colours, petunias seem to have fallen from favour in recent years

Petunias are a bit of a conundrum. For a start they are not really annuals but tender perennials. This fact has led to the demise of the seed-raised petunia as plant breeders worked hard to produce sterile hybrids that had to be propagated vegetatively so we had to buy new plants each year. The first of these were the Surfinias (TM) which took the gardening world by storm in the 90s. Everywhere you looked there were cascades of the most intense (or horrific) magenta purple pouring out of hanging baskets and wall planters. As a source of colour they were incredible. As a money spinner they were perfect; protected by plant breeders rights with royalties for every plug plant sold, they must have made a fortune. They were rapidly followed by a host of others, including the wonderful British-bred double Tumbelinas, and the colour range increased to include almost unimaginable colours and combinations.

Seed producers rose to the challenge too and were soon producing seed-raised kinds with enormous vigour. PanAmerican Seeds introduced the Tidal Wave series, often sold as a climbing petunia. If caged, plants can reach 1m high but otherwise make large, spreading mounds. Others in their range include the flat, spreading Wave series and the more extensive Easy Wave and smaller Shock Wave ranges. 

This is all so different from when I started gardening. There were two types: the Grandifloras, which were the only ones I liked, with large and often frilly flowers and the Multifloras with more, but smaller flowers. Both needed good weather and the flowers turned to beige mush when it rained, but especially the Grandifloras which were glorious when the weather was dry but a washout when it was a washout!

A lot of effort has been made to make seed-raised petunias weather resistant but when looking round trial fields in bad weather it has to be admitted that they are still not as reliable as some other bedding plants.

Poor petunias do have a bit of a problem when it comes to public perception because their very brightness can be seen as vulgar and I confess that I myself sometimes use a comparison with petunias as derogatory. But this is not really deserved.

There are 20 or so petunia species, native to South America and in the Solanaceae. They are low, spreading perennials that frequently tolerate drought but most do not tolerate frost. Our garden petunias are usually called P. x hybrida or P. x atkinsiana, a hybrid of the white, fragrant P. axillaris and the pink P. integrifolia. Few other species have been used in hybridising although P. exserta was discovered in southern Brazil in 1987. Only 14 plants were found but it was introduced into cultivation in 2007 and is now available as seed. It has red flowers and is the only species to be pollinated by humming birds rather than insects. It is also the only species with red flowers and with different pigments to other species so there may be potential for new colours in hybrids. Even more extraordinary is P. patagonica which is an alpine forming tight tufts with tiny leaves and curious, beige, darkly veined flowers. I saw a plant at the Alpine Garden Society show at Malvern Flower show many years ago and was captivated, but this is a specialist, alpine house plant, not for the garden – unless you live in Patagonia I assume.

Petunias are easily raised from seed but the seeds are tiny and the F1 hybrids are expensive. The seeds must be sown on fine, moist compost and not covered as they need light to germinate. They also need warmth – 20c is perfect. Seed should germinate in two weeks. The seedlings are tiny at first and prone to overwatering and cold – damping off is common.

The plants are clammy, with sticky hairs and deadheading is a messy business. You need to remove the seedpod aand calyx to prevent seed forming and this means pinching off the old flower and not just tugging at the faded petals. A feature of petunias that is not always appreciated is their scent. This alone hints at their relationship with the Solanaceae because it is rather cloying and heavy, with distinct hints of datura or brugmansias. It is especially heavy in the purples and whites but it is worth giving the flowers a sniff when buying plants.

Who knows where petunias will go next. We already have yellow flowers, green edges and blacks – as black as any flower I have seen. A few years ago ‘Night Sky’ (above) was introduced with dark blue flowers irregularly spotted with white. I was immediately captivated, but just as quickly turned my back – it looked too much as though badly attacked by mildew. A pink version followed. Novel as these all are, I find that they are difficult to use in the garden.

I struggled with the blacks till I decided that silver foliage was the answer but some of the new combinations have me scratching my head.

But I will never be able to resist a well grown basket of pink or white petunias, with some verbena and lobelia for contrast and perhaps the simplest, well grown, are the best.

how to grow petunias