1. ‘Sweet Kate’ Spiderwort

Name: Tradescantia andersoniana ‘Sweet Kate’

USDA Hardiness Zones: 5 to 9

Size: 1 to 2 feet tall and wide

Conditions: Full sun to partial shade; moist, fertile soil

‘Sweet Kate’ spiderwort is a fast-growing perennial that is perfect for filling in those first- and second-year gaps in a newly planted bed or border. From a 1-gallon pot, it will reach its mature size by the end of the first season, and its cobalt blue flowers provide a perfect contrast to its golden yellow foliage. If the plant begins to look tired mid­season, simply shear it back to 2 to 3 inches tall (foliage and all), fertilize, and water; within a few weeks’ time, it will be lush and flowering again. The plant loves moisture, especially if it’s sited in full sun.

2. ‘Powis Castle’ Artemisia

Name: Artemisia ‘Powis Castle’

Zones: 6 to 9

Size: 1 to 2 feet tall and 2 to 3 feet wide

Conditions: Full sun; fertile, well-drained soil

For fast growth and superb silvery foliage, there is no better plant than ‘Powis Castle’ artemisia. An almost shrublike perennial, its fine silvery foliage makes it the perfect foil for other garden plants. While many artemisias are either invasive in the garden or are intolerant of heat and humidity, ‘Powis Castle’ is perfectly behaved and stands up to heat and humidity without melting. Pair it with summer- and fall-blooming salvias (Salvia spp. and cvs., Zones 5–11), coneflowers (Rudbeckia spp. and cvs., Zones 3–11), and other sun-loving plants. Its fragrant foliage is a nice added touch, and the plant is terrific for planting near a path where brushing past it will release its fragrant essential oils.

3. Cardoon

Name: Cynara cardunculus

Zones: 7 to 9

Size: Foliage up to 3 feet tall and wide; flower stalks up to 6 feet tall

Conditions: Full sun; moist, well-drained soil

For garden impact, there may be no better plant than cardoon, and for fast growth, it ranks near the top. This plant will spend most of its life as a large but tidy mound of architectural, silvery white foliage, which will be the envy of your gardening neighbors. In its second year and beyond, tall sturdy bloom stalks will emerge in late spring and early summer to reveal 6-inch-diameter, thistlelike purple blossoms. Before the flowers go to seed, cut the entire plant (foliage and all) completely to the ground. Within a few weeks, new foliage will grow and remain beautiful until a hard freeze knocks it down in late autumn.

4. ‘Black and Blue’ Blue Anise Sage

Name: Salvia guaranitica ‘Black and Blue’

Zones: 7 to 10

Size: 3 to 4 feet tall and wide

Conditions: Full sun to partial shade; moist, well-drained soil

If you love butterflies and hummingbirds, ‘Black and Blue’ blue anise sage will soon become one of your best garden friends. It will grow to its full size in the first season, and will flower from June until frost without stopping, easily filling in any gaps that might be present in a newly planted garden. ‘Black and Blue’ thrives in full sun but will tolerate light afternoon shade, and it will reward any extra fertilizing and watering with copious quantities of cobalt flowers on long showstopping spires. One of my favorite summer activities is walking through my garden in late afternoon to watch the hummingbirds fight over this plant.

Troy Marden is a plantsman and garden designer who has lived and gardened in Nashville, Tennessee, for 20 years.