Say you're looking to soften a fence or add height to the back of a border, and you want to do it quickly, like in a few weeks. Your options? Aside from expensive evergreen shrubs or trees, consider these fast-growing annuals that will reach respectable heights by midsummer.
Angel’s trumpet (Datura metel) Large, trumpet-shaped flowers of purple, yellow or red dangle from tall plants with coarse leaves; all plant parts are poisonous; tolerant of partial shade; grows 4 feet tall.
Zebra mallow (Malva sylvestris 'Zebrina') Upright bush covered with maroon-striped purple flowers; attracts butterflies and hummingbirds; requires full sun; reaches 2-4 feet, 18-24 inches wide.
Mexican sunflower (Tithonia rotundifolia) Bright orange flowers with velvety petals are more than 3 inches across. Plant 5-7 seeds per square foot, and by late summer, you'll have a beautiful haven for butterflies, especially if you have four square feet of soil to devote to these heat- and drought-tolerant plants. Requires full sun; grows 3-6 feet tall.
Tree mallow (Lavatera) Jewel-toned flowers resemble those of hollyhocks. Sow seeds directly in the garden in early May. Requires full sun; reaches 3-4 feet tall; 1-2 feet wide.
Kiss me over the garden gate: (Persicaria orientalis) is an old-time annual with pink flowers that hang in chains from stems. Self-sows; full sun; grows 12 feet tall, 2 feet wide.
Cosmos (Cosmos bipinnatus). Pink, white or red flowers are held above stems on plants with fern-like foliage; requires full sun; may need staking; grows up to 4 feet tall.
Flowering maple (Abutilon hybrid) is not related to maples, but leaf shapes are similar to those of the namesake tree. Varieties include those with white, pink, orange and red flowers, some with variegated foliage; for sun or part shade; grows 2-6 feet tall.