Q: I have a small, sunny courtyard where I want to make a knot garden, but our harsh winters kill most of the evergreens recommended for dwarf hedges. What can I do? — Tessa Hill, Plymouth, Minn.
A: Your choice of evergreens is limited indeed, but you can stretch the knot garden tradition by substituting deciduous shrubs or annuals. There are many small plants — topping out at 2 to 3 feet — that will serve to form the intricate, twisting borders that define the form. For evergreens, you might try hardy dwarf varieties of boxwood, such as Buxus sinica var. insularis ‘Wintergreen,’ ‘Winter Beauty,’ and ‘Tide Hill,’ or Buxus ‘Green Mountain.’ Or, for a silvery look through the winter, you can plant dwarf lavender cotton, Santolina chamaecyparissus. The variety ‘Nana’ is hardy to at least zone 4, if it has well-drained, not-too-fertile soil.
If you’re willing to sacrifice winter attraction, why not try some deciduous shrubs? Japanese barberries, Berberis thunbergii, take pruning well, and the cultivar ‘Crimson Pygmy’ makes a lovely miniature, red-leaved hedge. The dwarf privet Ligustrum vulgare ‘Lodense’ offers dark-green leaves for contrast. Or you can impart a stylish look with the semievergreen, fragrant foliage of hyssop, Hyssopus officinalis, or the gray foliage of an English lavender, such as Lavandula augustifolia ‘Grey Lady’. Many annuals can be pressed into hedge service nicely as long as you don’t mind replanting them each spring. The dwarf basil Ocimum basilicum ‘Spicy Globe’ has a dense mounding habit, while the taller variety ‘Red Rubin’ sports attractive maroon leaves. For even more color, use the red or yellow calico plants Alternanthera ficoidea ‘Brilliantissima’ or ‘Aurea.’ After you’ve established the hedge border, fill in the geometric patterns with dense, fine-textured carpets of colorful annuals or herbs such as the thyme Thymus x citriodorus ‘Doone Valley,’ or wild marjoram, Origanum vulgare.