By John Valleau, Valleybrook Gardens/Heritage Perennials

As perennial gardening continues to increase in popularity, gardeners are beginning to push the limits of traditional ways of using perennial plants. Growing perennials in containers is one trend that is causing much “buzz” in the gardening world, and it seems that nearly every consumer magazine has done an article on this very thing in the last year or two.

     Container gardening has many benefits. It allows plants to grow where there is no bed of soil available, anywhere from balconies, decks and entranceways, to window boxes and hanging baskets. In recent years, the selection of annual plants suitable for container gardening has grown significantly, many of them propagated vegetatively and marketed under successful programs like “Proven Winners.” So gardeners are now getting used to more unusual plants for their containers, and look beyond the “traditional” for ideas and combinations to build their own one-of-a-kind effect.

     Perennials are ideal for containers, offering a huge range of flower and foliage colour and texture, as well as a range of blooming times so pots are constantly changing over the season. By combining them with annuals, herbs or bulbs, a nice selection of plants may be easily grown in a condensed area, a sneaky way of packing lots of variety into a small garden space. An aging population of gardeners ensures that container gardening will be on the increase. Gardeners with restricted mobility find containers easier to care for, and the plants within them closer to see, touch, feel and smell.

     Containers, however, also create a bit of a dilemma in terms of winter care. Basically, when perennials are in pots, the gardener has four choices for overwintering them.

• Do nothing and take your chances. Simply leave the pots alone and see what happens. This can be successful, when a selection of extremely hardy plants is used. If you live in Zone 5 for instance, using perennials rated hardy two full zones colder, (in this case, Zone 3) should give fairly good results. The reason is simple; when plants grow in pots, the soil temperatures during winter will go much lower than they would in the open ground, exposing the roots to more extreme conditions. Also, there may be alternating freeze/thaw conditions to deal with, depending on the climate and sun exposure of the container.
  
  
• Move containers into an unheated garage or garden shed in late fall. Water them one last time, and then ignore them until April. In spring, a thorough watering and top dressing of slow release fertilizer will get them off to a good start. They can then be moved right outside. Again, choosing plants rated hardy to a zone or two below where you live will give the best results.
  
  
• Dismantle containers in the fall. Transplant the perennials into the garden, then either move them back into the pots in spring, or choose new plants next year.
  
  
• Bring them into the house. This works particularly well with pots of tender perennials like Canna Lilies or Colocasia, which can be cut back hard, allowed to dry out and just stuck in the basement, pot and all. Hardy outdoor perennials usually don’t care for warm indoor temperatures, and if they continue to grow through the winter, a bright light source is required.
  
       Never before has the selection of pots and containers been so good, and in a range to suit every budget. Terra cotta clay pots will often crack and break during the winter, unless plants are wintered in a frost-free area. Thick plastic pots of all kinds are less prone to breaking, and now come in a vast range of colours and styles. Even cheap plastic pots may be faux finished, both to spruce them up and suit every possible colour scheme. Wood and metal pots are also good. What is most important is the size of container, if plants are to survive over the winter. Choose something at least 45 cm (18 inches) in diameter and 30 cm (12 inches) deep. Bigger is better.
  
       The soil used in containers should be well drained, yet fairly lightweight, if pots are going to be moved frequently. I like to blend two parts commercial potting mix with one part topsoil. The topsoil seems to add some water-holding ability, as well as supplying nutrients and acting as a kind of buffer when the gardener forgets to fertilize. The extra weight of topsoil also helps to prevent pots of tall plants from falling over in the wind.
  
  Alchemilla mollis (Lady’s Mantle)
  Zones 2 to 9
  Height/Spread: 30 to 45 cm (12 to 18 in.)/45 to 60 cm (18 to 24 in.)
  Lady’s Mantle (Alchemilla mollis) is extremely hardy, and a nice filler plant for pots. Adaptable to most garden conditions, Alchemilla mollis displays scalloped green leaves, covered in a soft down, and offers yellow-green blooms from June to August.
  
  Carex comans (Sedge)
  Zones 6 to 9.
  Height/Spread: 20 to 30 cm (9 to 12 in.)/30 to 45 cm (12 to 18 in.)
  Forming to low to medium sized tufts, sedges are frequently used in groundcover plantings, with blooms appearing June to July.
  
  Artemisia ludoviciana ‘Valerie Finnis’ (Silver Sage)
  Zones 4 to 9
  Height: 45 to 60 cm (18 to 24 in.)
  Artemisia ludoviciana ‘Valerie Finnis’ makes a stun­ning focal point of silver in a container with purple Osteospermum, with its very wide silvery leaves. ‘Valerie Finnis’ is similar to ‘Silver King’ though more compact and less invasive. It has been touted as the best grey foliage plant available.
  
  Artemisia stelleriana ‘Silver Brocade’
  Zones 2 to 9.
  Height/Spread: 15 to 30 cm (6 to 12 in.) /60 to 75 cm (24 to 30 in.)
  A low, compact selection, similar in appearance to Dusty Miller, the scalloped silvery-white foliage makes a delightful contrast when teamed with the bronze-leaved Carex comans. They may be wintered indoors in a sunny window.
  
       Pots of hostas are a good solution to dry shade areas under trees, where little else will grow. Surround them with a tough groundcover like Lamiastrum galeobdolon ‘Herman’s Pride’, Hedera helix ‘Baltica’, Lamium maculatum or Vinca minor.
  
  Hosta ‘Great Expectations’
  Zones 2 to 9.
  Height/Spread: 75 cm (30 in.)/120 cm (48 in.)
  For shadier gardens, Hosta selections like ‘Great Expectations’ are stunning in pots. Displaying deep blue leaves with an unusual bold centre variegation of golden-yellow, later changing to creamy-white, ‘Great Expectations’ needs some sun for best colouration. Displays near-white flowers in June.
  
  Lamiastrum galeobdolon ‘Herman’s Pride’
  Zones 2 to 9.
  Height/Spread: 20 to 30 cm (8 to 12 in.) / 30 cm (12 in.)
  Blooming May to June with small but showy yellow flowers and pointed leaves, heavily veined with metallic silver, Herman’s Pride makes an attractive groundcover as it forms a neat, non-spreading mound. Suitable for containers, shady borders and woodland settings.