When given proper conditions and care, summer alliums are stellar, reliable performers in the landscape. Here are some insights into growing summer alliums that can help you manage and enjoy these perennials to the fullest. See the best varieties of summer alliums from the recent plant trial by Chicago Botanic Garden.

Where to plant summer alliums

While there are woodland species, these summer-blooming alliums are best grown in full sun and average to fertile well-drained soil. Avoid heavy clay and soggy conditions. These plants are drought tolerant once established.

How to plant alliums

The summer alliums featured here are generally sold as rhizomatous plants. You will find them potted in nurseries in spring, and they can be planted much the same as any other potted perennial.

Pruning summer alliums

Alliums make excellent cut flowers for fresh and dried floral arrangements. Beyond that, deadhead as desired. Persistent fruits can be ornamental in the garden late in the year, and while some hybrids are sterile, reseeding is a real issue for other alliums. If desired, scraggly foliage can be cut back after flowering to encourage a fresh surge of growth. Otherwise, cut faded dormant leaves back to the ground during fall cleanup.

Pests and diseases to look out for

Alliums are rarely troubled by pests and diseases. High soil moisture, however, can lead to rot, mildew, and fungal leaf spots and molds. Plants are occasionally susceptible to onion
fly and thrips.

Dividing alliums

To make more plants, manage overgrown clumps, or rejuvenate tired alliums, divide plants in early spring. These plants are pretty forgiving; you can also divide them after flowering in late summer or early fall if you do not mind them looking a little rough for the remainder of the gardening season.

Do deer eat alliums?

Bees and butterflies are tireless visitors when alliums are flowering. Their foliage—pungently aromatic when bruised or broken—deters most rabbits and deer from munching.

Anatomy of a summer allium

1. Umbel inflorescence—A flower is comprised of a cluster of stalks that radiate from a central point.

2. Simple basal leaf arrangement—The cylindrical linear leaves grow only from the base of the plant in a rosulate or whirled configuration.

3. Bulbous rhizomatous root system—Vestigial bulbs are connected to rhizome root structures.

Bloom up-close

Single flower: Allium umbel flower heads are made up of many small, individual single flowers.

Fruit: After pollination, each single allium flower turns into a small fruit or seed capsule, which often provides additional ornamental interest.

Seed: Within each fruit the tiny black seeds are revealed as the fruit dries and splits.

Richard Hawke is an expert plantsman and the director of ornamental plant research at the Chicago Botanic Garden in Glencoe, Illinois.

Illustrations: Jessica Daigle