Architectural Plants

I?m a fan of huge plants. Placed exquisitely, they can perform wonders in the dullest of gardens.

Alas, we seldom use them in imaginative ways. These giants are usually called architectural plants. I?m not especially fond of the term, but it does have some logic: these plant do have an architectural function. They can provide structure when there?s no money for a waterfall or gazebo or even a fence, they can provide divisions between one part of the garden when you haven?t got a trellis. Unfortunately, we (and I count myself in with the offenders) tend to stick them in the back of a border as a foil for all the medium and smaller plants in front of them.

That seems ho hum given how they could be used. There?s possibility of real drama if you drag some of these plants into the centre of a long border, or place them at either end. They are an excellent way of breaking up a seemingly static perennial area and ideal for any needed vertical accents. One great plant can become a framework for a whole mess of other plants around it. How about a screen? Or breaking up a flat space into garden rooms? Get some big plants.

These huge leaves help a plant trap energy but they will also wilt pretty quickly if water becomes scarce. I?ve always used at least one such plant in each area as an indicator plant to let me know when there?s a serious drought starting to happen. So don?t put these behemoths in a drought ridden garden leave them to shade and damp areas. Or use the ones that are hairy or felted which helps hold in moisture for a xeriscape area of lots of sun and no water.

In Victoria and Vancouver there is a whole different concept of what constitutes a big plant. They suffer from gigantism out there, poor things, and though the plants suggested here won?t get to the gargantuan heights they attain in those places, most other areas won?t do too badly by these. Here?s a glossary of elegant large plants suitable for almost any size garden put in the right place:

  • Acanthus hungaricus: will grow in either sun or shade though I find mine does well mostly in shade with late afternoon sun. It?s a stunner: big glossy green dissected leaves and a strange spiky hooded mauve and white bracts that bees seem to love. It?s relative A. mollis is not as interesting to my eye but it is much larger (up to l.5 ft). In warm climates the latter is inclined to be a pest. The Acanthus leaf is the motif found on steles all over the Mediterranean. Either species makes a good container plant. Ignore zones on this one, if you have a good snow cover they will survive in Z5.
  • Maclyea cordata: will grow up to 3M high in either sun or shade. There?s a serious caveat with plume poppy because it will move quickly and spread out to make a colony. The leaves are sort of fig like, and the majestic plumes rising above them in summer a pleasant ecru. This is definitely to be used only as a background plant, screen or in a very large container.
  • Gunnera has monster leaves up to 2M wide and it?s a staple on West Coast and now in some sheltered east Coast gardens where it grows well. The deeply cut leaves are stunning but it?s not a plant to be used casually it can reach 2.5M high without any trouble but a dramatic wet area plant. In coolish areas the crowns should be protected in the winter.
  • Verbascum: the vertical accent par excellence. The felted grey leaves begun at a rosette on year and rise up 2 m the next (it?s a biennial). V. Olympicum has silver gray foliage, bright yellow flowers clustered in a dense form around the spikes. V. Bombyciferum ?Arctic Summer? will grow to 2.5M and spread 50cm in the full sun. It blooms with yellow flowers in June and July. This plant has a rosette one year, the big stalks the next and may seed itself so it seems like a perennial. It also may be monocarpic: blooms then croaks.

Grasses such as Miscanthus sinensis ?Gracimillus? look spectacular set into mixed borders. It will reach at least 2M. But it doesn?t matter what grasses you choose, they will be striking because they provide such a splendid contrast to shrubs and perennials. which is not quite as big but just as striking.

Other grasses that reach the 2M mark are:

  • Arundo donax (Z 7 and warmer);
  • M. S. ?Morning Light? is still one of my favourites because it has a subtle white margin and
  • ‘Silberfeder? has pale pinky brown panicles which stay all winter.
  • Molinia caerula ?Karl Foester? has arching purple spikelets in autumn that look smashing all winter long. I use it almost as a scrim to look at the garden through.
  • ?Sky Racer?, another superb molinia, will grow to 2.2M

Annuals like Canna have been used so hatefully, marching stiffly along the middle of public plantings it?s a wonder any of us can stand them. But when they are tucked into a border planting scheme they can look gorgeous. C. ?Striata? has amazing creamy veins and would look good as a companion for a plain green or brilliant yellow plant. Melianthus major is a dynamic silver grey shrub which is just about the ideal container plant but I like to toss it in with other plants such as campanulas or grasses just as a contrast. The grey to silver 30 to 50cm wide leaves, deeply cut with serrated edges and can get up to 3M high, large enough to hold up everything around it.

Start with one or two of these big plants and see how they will refresh a dull border. Another value is that they come into their own in August which means there is something new and exciting when other things may be limping along. Experiment with the annuals to get a feel for the scale of these plants and then scatter them around gracefully. They will provide a refreshing contrast to everything else you put in the garden.