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US National Arboretum


The Right Rosemary

image of Rosemary 'Baby PJ' Rosemaryís classic flavor enhances many kinds of food, making it a popular culinary herb in the garden. Not only are the plants beautiful, but, planted near the kitchen, they provide a fresh source of edible leaves at your fingertips.

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In the National Herb Garden, we grow 51 different rosemary cultivars representing the many forms, flower colors, fragrances, and varying cold-hardiness.

Plants may be upright, lax and sprawling, or
prostrate, almost hugging the ground;
leaves may be broad, thin, or short and stubby;
flowers are generally blue, but also come in pink or white; and fragrances vary from plant to plant as well, ranging from a warm, rich pine to almost unnoticeable.

If thatís not enough to consider, rosemaryís hardiness can be as variable as its physical traits. To help illustrate this, all of the plants in our collection are left outside through the winter until early April. Any cultivar which survived the cold temperaturesówith or without damageóand those that did not will be plainly obvious. Some cultivars die after a few hard frosts, while others remain unscathed by Washington, D.C.ís tough winters. As a precautionary measure, we take replacement cuttings of each plant in early summer. These are grown on in pots and protected during the winter for the following year.

The two most commonly grown hardy rosemaries are Rosmarinus officinalis 'Arp' and R. officinalis 'Madelene Hill' (syn. 'Hill Hardy'). But, in the National Herb Garden, we have found many other cultivars which make it through the winter with little or no dieback:

As a rule of thumb, cultivars with thinner leaves and lighter flowers are hardier, and prostrate types are the least hardy.

No matter what cultivar is grown, there are a few practices that will help with winter survival. It is best to plant rosemary in the spring so the roots have a long, warm summer to become established, and place it in a location that gets full sun throughout the year. A site sheltered from winter winds is best. In heavy, clay soils, mulching with gravel will reflect light and heat back into the plant and help prevent soil-borne diseases from splashing onto the leaves.

The rosemary collection in the National Herb Garden is a valuable tool for evaluating which rosemary is right for you. We encourage you to rub and smell the different cultivars to find the fragrance you like best and to choose a growth habit or flower color that suits your gardening tastes. If you want a hardy cultivar, look for the largest plants in the collection which have survived many winters in the ground. Whichever cultivar you choose, it is sure to provide you with pleasure as it grows throughout the season.

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Last Updated   August 26, 2005 4:07 PM