After filling my garden with roses, delphiniums, irises, daylilies, buddleia, heliotrope, and a host of other plantings, I ran out of space, but not out of the desire to grow more plants. So I turned to plants called standards or patio trees. What are they?
Most gardeners are familiar with standard roses or "tree roses." But growers produce other plants on trunks in a similar fashion. With their colorful flowers or foliage atop a branchless trunk no thicker than 1 to 2 inches, standards provide an unusual form in the garden or in containers.
Most nurseries offer several kinds of standards. Some, such as lilac and smokebush, are hardy in the garden even where temperatures fall as low as -25° F. Some of my other favorites include include weeping pussy willows (Salvia caprea 'Pendula') on a 3-foot rootstock, and green-leaved golden shrub daisy (Euryops pectinatus 'Viridis') as a small tree. Other plants include camellias (C. sasanqua), sweet broom (Cytisus racemosis, also called C. spachianus), rose of Sharon (Hibiscus syriacis), spearmint juniper (Juniperus chinensis 'Spartan'), and wisterias (W. sinensis).
Standards require regular pruning. Most of them flower on new wood, so prune them after a flower flush in spring to maintain the desired shape. Some patio trees, such as wisteria and weeping pussy willow, are vigorous growers. Prune them by shortening and untangling long branches as necessary. Once their form is set, however, they require just enough pruning to maintain an attractive appearance.
Planting low-growing annuals or perennials under container-grown standards enhances their form. Try combining standard roses with miniature rose bushes or low-growing cascading plants such as cranesbill (Geranium sanguinum), or petunias. When planting a row of standards along a drive or entryway, avoid a regimented look. Instead, use companion shrubs such as heliotrope (Heliotropium arborescens) or rugosa roses (R. rugosa) or perennials such as daylilies, delphiniums, larkspur, or salvias to camouflage the standards' bare legs for an interesting two-tiered color effect.
Standards are easy to manage if you live in USDA Hardiness Zone 9 or 10. You can leave them outdoors all winter. Where winters are colder, more aggressive winter protection may be necessary. Check with your nursery about the standard's hardiness. Most often it is easiest to protect container-grown standards over the winter by moving them into a protected garage or basement.