Flowers for flower boxes can be tall or short, trailing or contained, annuals or perennials. The best flower-box flowers are those that can mix well with other flowers to provide a variety of colors, shapes and fragrances. Flowers that require relatively little care are well suited to flower boxes.
Sweet marjoram is also known as wurstkraut and Origanum majorana. It is a fragrant, hardy perennial that is great for container use. It can get 1 to 2 feet tall and is multi branched. Leaves are 1 inch long and fragrant, and the plants produce tiny flowers. Plant a sweet marjoram in well-drained soil with a slightly high pH, in full sun to almost full sun. Water the plant frequently. Propagate via seed or by cuttings. This is great in flower boxes as it can be used as a cooking herb, too.
Mealycup sage is also known as blue sage and Salvia farinacea. It is an easy to grow perennial that may be grown as an annual. It is good for container and flower box use. It ranges from 1 to 4 feet high. Blue flowers are on spikes beginning in spring. Leaves are long and green on the top and silver on the bottom. Plant a mealycup sage in average soil and full sun, with a bit of afternoon shade for hot climates. Well-drained soil is best. Propagate via seed or spring clump division.
Lily of the Nile
Lily of the Nile is also known as African lily and Agapanthus praecox, and is an evergreen perennial good for containers. Strap-like leaves get a foot long, and the plants produce trumpet-shaped blue flowers 1 to 2 inches wide. Flowers are in clusters 6- to 12-inches wide. Flowers will start showing in summer. Plant a Lily of the Nile in full sun with regular watering. Propagate via clump division in spring or seed (wait two or three years for the plants to flower).
Angelonia is also known as Angelonia angustifolia. It is a perennial good for container gardening. Leaves are 2 to 3 inches long and smooth, with an apple like scent. Blue to lilac flowers 1 inch wide are on spikes 8 inches long. Flowers appear all summer. Plant an angelonia in full sun and water regularly. Propagate via root mass division, seed, or from tip cuttings.
Madagascar periwinkle is also known as rose periwinkle and Catharanthus roseus. It is a fast-growing, vinelike perennial that is drought tolerant and good for containers. It will reach 2 to 3 feet tall and the same in width. Leaves are 2 to 3 inches long. Flowers are pink, red, white, and purple and 1.5 inches wide, and will bloom throughout summer. Plant a Madagascar periwinkle in poor but well-drained soil in full sun or partial shade. Propagate via seed or spring and summer cuttings.