Gardening Best Friends: Allium and Roses

Gardening Best Friends: Allium and Roses

June 3 2015 RHR 114Is your garden plagued by aphids, slugs, cabbage worms, or other pests? If so, Allium may be the solution you have been waiting for. The ornamental onion genus, Allium¸ which includes chives, garlic, leeks, and shallots is regarded as a broad spectrum natural insect repellent. Thus Allium is planted as a beautiful, dramatic bedfellow of roses throughout the newly renovated sustainable Dean Bond Rose Garden.

The low profile of Allium christophii combines well with roses in the Dean Bond Rose Garden. photo credit: R. Robert

The low profile of Allium christophii combines well with roses in the Dean Bond Rose Garden. photo credit: R. Robert

Many unwelcomed pests are attracted by odors emitted from plants. Members of the allium family, Amaryllidaceae, emit a sulfur/onion odor that masks the smell of other plants, but is undetectable to humans, so alliums serve as a good repellent to aphids, a common pest of roses.

Allium angulosum 'Summer Beauty' blooms during the heat of the summer, July to August. photo credit: R. Robert

Allium angulosum ‘Summer Beauty’ blooms during the heat of the summer, July to August. photo credit: R. Robert

The benefits of our “stinky friends” also extend below the soil. They keep subterranean pests such as grubs and nematodes at bay. Grubs grow into Japanese beetles which burrow into rose buds to eat the developing flowers. Another reason roses and alliums should be garden best friends.

Allium 'Gladiator' attracts all types of pollinators and beneficial insects. photo credit: R. Robert

Allium ‘Gladiator’ attracts all types of pollinators and beneficial insects. photo credit: R. Robert

In addition to the natural repellent mechanism, alliums are beautiful in the landscape. The long-blooming flowers range from large to enormous purple ball-like blooms making a striking presence in the landscape. The flower heads also dry nicely creating multiple-season interest.

Along with beauty, Allium offers the full package. It attracts beneficial insects such as hoverflies, bees, and parasitic mini wasps. For example, parasitic mini wasps feed on the pollen of Allium and other small flowers. The larvae of the wasps feed inside beetle grubs and aphids, killing many unwanted pests.

The purple of Allium 'Gladiator' compliments the colors various colors of rose blooms. photo credit: R. Robert

The purple of Allium ‘Gladiator’ compliments the many colors blooming in the Dean Bond Rose Garden. photo credit: R. Robert

The ornamental onion is available in a variety of sizes and bloom times. This beauty and function has made it a staple in our efforts to create a sustainable rose garden. Add it to your garden mix and you will not be disappointed.

Adam Glas
aglas1@swarthmore.edu
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