By Stan Barrett, Colorado Master GardenerSM, Colorado State University Cooperative Extension, Denver County
The practice of growing roses in containers and the reasons for doing so have expanded in recent years. Not long ago roses were grown in containers almost as a last resort, because the gardener had run out of space or was limited to a patio or balcony. Roses that were regarded as suitable were generally limited to standard ("tree") roses, miniatures and small floribundas. Nurseries have sold containerized roses for many years but they were usually removed from the pot and planted in the ground as soon as possible.
Why Use Containers?
Lack of space is still a strong motivation, of course, but now the types of roses that are grown in pots for the long term include larger floribundas, hybrid teas and grandifloras, and even some of the modern shrub roses. This trend has been helped along by the introduction of affordable, large, lightweight pots and improvements in planting mixes.
Recent developments in the Horticultural Therapy field have shown how gardeners who find it physically difficult to work at ground level can continue to pursue their hobby with containerized plants, since they can be located at a tabletop height.
Rose standard, clay pot sits on table
Another important reason for growing roses in pots, which is becoming more popular each year, is to make it easier for the gardener/designer to assess the suitability of a new rose in the landscape. The compatibility of its color, size, form and all-round quality with the existing plantings can be tried out by placing the containerized rose in its proposed location for a year or longer before installing it in the ground.
Rather than buying containerized roses, many gardeners now prefer to buy bare-root roses and pot them up themselves, using their favorite brand of high quality growing medium. Then they carefully nurse the new roses along, providing the proper amounts of water and nutrients, until planting time arrives. This approach involves more work but offers the best chance of developing healthy roots and top growth.
What Type of Container is Best?
Most kinds of containers (which can include pots, tubs, troughs, hanging baskets, etc.) work well for roses, though most experienced gardeners have their favorites. The important requirements are that the container must be big enough to allow for proper root development and it must provide good drainage. It should also have a wide enough base to resist being blown over in a strong wind!
Pots made of terra cotta, glazed ceramic, plastic, wood or even (for short-term use) biodegradable fiber are the containers most often used, with the ubiquitous black plastic nursery pots leading the way. Take care not to use a saucer underneath the pot, which would be an invitation to root rot!
The size requirement is dictated by the anticipated mature size of the plant, of course, and it is better to err on the generous side. This also ensures that the pot will hold enough soil to avoid drying out too fast. To accommodate a hybrid tea, large floribunda, grandiflora or shrub rose a 15-gallon pot is recommended. One of the smaller floribundas would be quite happy in a 10-gallon pot, while most miniatures fit well in the 4- or 5-gallon size. For temporary use, such as trying a new rose in the landscape, even the first group can be grown for a year or two in a 10-gallon pot.
Miniature rose in plastic pot
What Planting Medium Should be Used?
This is another area in which personal preference reigns. Some rose growers insist on using a sterile soilless potting medium, with up to 50% Perlite added to lighten the mix and provide faster drainage. Others report success using a made-up mixture of, for example, 30% screened compost plus 30% Perlite plus 40% topsoil. To help root development superphosphate should be added to the mix (about ¼ cup for large pots, 1 tablespoon for smaller pots) and many rosarians also add a slow-release fertilizer.
For more detailed information on types of growing media, reflecting local availability, it is advisable to seek advice from your County Extension Office or a Consulting Rosarian living in your area.
Do Containerized Roses Need Special Treatment?
Cultural practice for roses grown in pots is different in some ways. One obvious difference is frequency of watering. Because it is essential to provide fast drainage the soil can dry out very quickly, so that daily watering is necessary in hot weather; in fact smaller pots may need to be watered twice daily during very hot spells. This in turn means that fertilizer applied to the soil will leach out rapidly, so more frequent fertilizing is necessary for best performance.
It is advisable to change the soil every three years or so, by which time it is likely to show a buildup of soluble salts left by the fertilizer.. At the same time the roots should be inspected and trimmed back if the rose is becoming root-bound.
There are a number of advantages enjoyed by the gardener who uses containers. For instance, the pots can be moved around to find out which exposure, in terms of sun and shade, best suits the rose. Concerns about freezing weather (or the dreaded hailstorms) can be addressed by moving the pot into a sheltered area. Treatment for pests or diseases is generally easier, since the rose can be isolated from the rest of the landscape for the required TLC.
Growing roses in containers offers some real advantages if you are running short of garden space, or if you find that working at ground level has become too challenging, or if you simply want to experiment with an easily changed garden design featuring new roses.
Large lightweight containers are now available which makes the potted rose easier to move around. Many types of roses have been found to respond well when planted in a pot. Cultural changes, compared with conventional "in ground" gardening, are minor and easily accomplished. In short, this method of growing roses can become a highly satisfying extension to the rosarians hobby.
Photographs courtesy of Judy Sedbrook.
© CSU/Denver County Extension Master Gardener 2010
888 E. Iliff Avenue, Denver, CO 80210
Date last revised: 01/05/2010