Prune to promote bloom
"Often and lightly" is the best pruning policy for all standards, according to Barron. Tree roses are no exception. "Hard pruning just encourages long shoots to form," says Carruth. Plants that flower almost continuously, like Paraguay nightshade (Lycianthes rantonnei), benefit from trimming as often as once a week. With shrubs that set buds once a year, like azaleas, wait until after bloom to shape.
Vigorous plants like bougainvillea occasionally need to be pruned hard. The nearly 40-year-old bougainvillea standard pictured above at Sherman Library & Gardens in Corona del Mar, California, is cut back by one-half to two-thirds every three to five years, according to John Bishop, manager of horticulture. The rest of the time, it is pruned lightly for shape. "If you want flowers, you have to keep pruning standards or your flower production will gradually decline," says Bishop.
Stake young plants
Standards are naturally top-heavy, especially when young. To keep their delicate trunks from snapping in the wind, support them with a sturdy wood stake or 1/2-inch-diameter galvanized pipe. As they mature, some plants develop trunks strong enough to support crowns. But if you live in an area with gusty winds, you might want to keep them staked indefinitely.
15 standard choices
You'll find many standards sold in 2- and 5-gallon containers. Tree roses usually come in 36- and 60-inch-high sizes.
Azalea, Southern Indica varieties
Cape mallow (Anisodontea hypomandarum)
Euryops pectinatus 'Viridis'
Flowering maple (Abutilon hybrids)
Gardenia jasminoides 'August Beauty', 'Mystery', 'Veitchii'
New Zealand tea tree (Leptospermum scoparium)
Paraguay nightshade (Lycianthes rantonnei 'Royal Robe')
Roses (floribunda, ground cover, shrub, and hybrid tea)