Have you ever taken something on and then wondered halfway through what possessed you? Tackling roses, for example, because they are so well known and then realising the diverse group that shrub roses presents.
The aim of this article is to give professional gardeners and other working horticulturists an overview of how the shrub rose category is broken down. It is an absolutely huge group - for a start, there are 100-150 species of roses and at least 13 shrub rose types, if not more.
For the purposes of identification, shrub roses are any rose plants that are bushy in habit and they are defined by being distinct from the Hybrid Teas, Floribundas and the climbers and ramblers.
They are usually larger than modern bush roses and have thornier stems, often with scented flowers. The old garden roses, so called because they were introduced prior to the 20th century, generally only flower once in the summer, but this is for several weeks and a shrub in full bloom in June and July is quite a sight. Some of the old roses also flower early, which can provide welcome colour - an example is Rosa xanthina 'Canary Bird' Award of Garden Merit (AGM), which flowers in May.
But there are repeat-flowering shrub roses, including the Portland Roses, Bourbons, Hybrid Perpetuals, Rugosas, Hybrid Musks and the Modern Shrub Roses. The latter group has a flowering habit similar to a Floribunda or Hybrid Tea, but they grow too tall for formal beds.
The English Roses from David Austin come into this category - they are the result of breeding work aiming to produce roses that combine the forms and fragrances of old roses with the repeat flowering of modern types.
Unlike modern bush roses, shrub roses generally flower on older wood and should be allowed to develop naturally, maintained by light but regular pruning. Shrub roses that produce a single flush of flowers should be pruned in late summer once flowering is over.
Take out dead, diseased or damaged wood. If the plant is becoming bare at the base, cut one or two of the older stems back to ground level and new growth will be encouraged. This method works for species roses, R. x alba, R. x centifolia, damasks, R. gallica AGM and Moss Roses.
Repeat-flowering shrub roses can have a little more attention. Regular deadheading will lead to later blooms. In late winter, cut some of the older stems back to the base, reduce strong new growth by up to one-third and shorten strong side-shoots to two or three buds. Carry this out on groups such as the Bourbons and Portland Roses.
One of the benefits of shrub roses is that they are tougher than Hybrid Teas and can cope in less than ideal situations, such as sandy soil or partial shade. But they prefer a well prepared, humus-rich soil. Adding mycorrhizal fungi is said to be very effective. Bonemeal can be dug in during February and rose fertiliser given in April and later in June.
Spraying programmes can begin in April, but growers are increasingly less concerned with fighting black spot and aphids, allowing beneficial predators and healthy growth to be the roses' best defence.
What the specialists say
- Michael Marriott, technical manager, David Austin Roses, Wolverhampton
"Shrub roses are wonderful. Today, they are the most popular group of roses with gardeners. They are an extremely diverse group, the flowers ranging hugely in size from a few centimetres up to 15cm or more.
"In terms of colour, you can find the whole range - white, all shades of pink, red, purple, yellow, apricot and even colours approaching blue. Some are very short at only 60cm high and others are huge, reaching up to 2.5m, and in shape from more formal and upright through bushy to arching.
"Gardeners particularly appreciate the shrub roses because they are generally much tougher, more reliable and healthier than the Hybrid Teas and Floribundas. Some do not repeat flower but others do. They are incredibly versatile.
"The two most important points for success are to choose a good variety - you want one that is known to be tough and reliable - and to prepare the ground well before planting using a generous quantity of well-rotted humus. The use of mycorrhizal fungi can be very effective too."
- Vaughn Limmer, head gardener and customer services, Peter Beales Roses, Norfolk
"Shrub roses are a wonderful way of bringing colour, scent and structure to a garden. There are shrub roses to suit any position or soil condition in your garden, from shady positions or light sandy soils to areas that get the full sun all day.
"They are great for group planting or even on their own as a specimen plant. Many can be used very effectively as a small climber on a panel or an obelisk.
"Two groups stand out for me. The first is the Hybrid Musks, introduced in the early 20th century by John Pemberton. This group includes varieties such as R. 'Prosperity' AGM, R. 'Penelope' AGM, R. 'Felicia' AGM and R. 'Buff Beauty' AGM. They are repeat-flowering, have a wonderful scent and can be used as small climbers.
"The other group I find very useful is the Portlands. This is a very old group, with plants that are all repeat-flowering and have a strong perfume. They are very useful for growing as hedging and ideal for planting in a pot. The first one was R. 'Duchess of Portland', introduced in 1790. Others include R. 'Rose de Rescht'."
- John Paisley, director, Wych Cross Garden Centre, East Sussex
"Generally, shrub rose have nosedived in popularity over recent years, but one way in which they are proving very useful for the modern, typically smaller, garden is as short climbers. If you have a 6in fence panel or two to cover, most true climbers are going to rapidly run out of space, become leggy and bare at the bottom and generally not prove very satisfactory.
"There are a number of shrub roses that make very good short climbers or are even better when grown in this way. A Shropshire Lad, 'Souvenir du Docteur Jamain' and Tess of the D'Urbervilles are on the list of those that we promote as climbing shrubs."
- Species and varieties
Species roses have simple, generally small flowers that are borne once in the growing season. The plants are usually large, sprawling shrubs. Examples include R. canina, R. arvensis, R. forrestiana and R. roxburghii. A good benefit is that some species provide early colour in the mixed border.
Old Garden Roses is a large group that encompasses all the shrub roses developed before the advent of Hybrid Teas and Floribundas. It includes the Gallicas, Albas, Damasks, Centifolia and Moss Roses that flower only once in midsummer. It also includes the Hybrid Musks and Rugosa shrubs that were developed more recently. These are both repeat-flowering.
Gallicas are bred from R. gallica AGM (H4), which is native to central and southern Europe. Flowers come in strong shades of deep pink, near crimson, purple and mauve in various combinations. R. gallica hybrids are usually compact, practically thornless, with rough leaves and semi-double or double blooms. Height: 60cm.
Damasks have highly-perfumed pink or white flowers. The overall plant is a bit weak, with arching weak stems, dull foliage and weak flower stalks. The flowers are borne in midsummer. Height: 1.5m.
Albas are tough and vigorous growers that may need to be kept in check with rigorous pruning but their benefit is their pest and disease resistance. They have soft, drooping grey-green leaves and fragrant pink or white flowers that appear in midsummer. Height: 1.8m.
Centifolias are also known as the cabbage roses for their double, globular flowers. While their flowers are attractive, they have lax stems that need support and require regular spraying and feeding.
Moss Roses are like their parent Centifolias, but they feature brown or green "moss" (sticky hair) on the sepals and flower stalks. They produce sweet-smelling blooms.
Portland Roses was the first new group to emerge after breeding work with Chinese garden hybrids that were repeat-flowering. They produce good, upright, bushy growth. Height: 1.2m.
Bourbons were produced after a cross between 'Old Blush China' and the repeat-flowering 'Autumn Damask'. This class marked the first real step towards modern roses. Usually largish shrubs, with many-petalled globular flowers, and almost all are very fragrant and mostly repeat-flowering.
Hybrid Perpetuals were popular with the Victorians because they had a summer flush of flowers followed by one in autumn, but they have now been supplanted by the Floribundas and Hybrid Teas. They are vigorous growers with an upright habit.
Rugosas are bred from R. rugosa, a very hardy shrub from northern China, Japan and Korea that is excellent for hedging because it can grow in almost any soil and has dense, thorny stems. The leaves are uniquely wrinkled and highly-resistant to disease. Produces fragrant flowers throughout the season and large hips. Many hybrids were produced around the turn of the 20th century. Height: 2.5m.
Hybrid Musks are a group of mostly large, gracefully-spreading shrubs that produce fragrant flowers and are repeat-flowering. Height and spread: 1.5m.
Modern Shrub Roses are descendants of Old Garden Roses. Mention must be made of the breeding work by David Austin that aimed to combine the forms and fragrances of old roses with the repeat flowering of modern types. This led to the group referred to as 'English Roses', which remains very popular today.
Particular thanks to John Paisley for his advice on rose classification.
Thank you to Floramedia, which supplied the images for this article from its photo library www.floramedia-picture-library.com.