During 2008 and 2009 I have written a series of articles about one the more romantic plants in the gardener’s palette. Another plant that comes from the same area and has many of the same properties is Rosemary. The genus is Rosmarinus and it belongs to the Lamiaceae (or Labiatae) family. Commonly referred to as the Mint Family. The Latin name Rosmarinus means 'dew of the sea' and refers to the fragrance and flowers from the masses of plants that used to grow on the cliffs on the edge of sea.
For the botanists amongst us the family is a member of the Division; Magnoliophyta. class; Magnoliopsida, the order; Lamiales. The family consists of more than 180 genera and 3500 species. These are from all parts of the world with the greatest number coming from the Mediterranean. There are several genera in Australia, with the most widely known being Westringia (the native Rosemary) and Prostanthera (the native Mint Bush).
Like lavender, rosemary likes full sun, good air movement and excellent drainage. They are more tolerant of wet and humid conditions but perform best in the traditional Mediterranean climate, As they come from that southern European region they have evolved on highly calcareous soils and thus need annual applications of Calcium to ensure optimum growth.
All Lamiaceae have aromatic foliage and produce very fragrant oils. Rosemary oil is popular for aromatherapy and again, like lavender the individual cultivars will each produce its own unique oil. Over the centuries it has been used as a landscaping plant but has really come to popularity as a culinary herb. Unfortunately not all cultivars have the same flavour. There have been many selections made based on oil content or on their flavour. The oil mix is similar to that of lavender and thus there are some culivars that are high in camphor or borneol. These varieties have a more ‘pine’ like fragrance and can be a bit tart when cooked. Other cultivars like Gorizia, have been selected for their flavour. They have less of these oils and more of the sweeter ones. The best part of the plant for cooking is the fresh young leaves. They can be used dry or fresh.
Also like lavender, there are many missnamed varieties of Rosmarinus. The genera comes from the Meditarranean rim and there are two species: R. officinalis and R. eriocalyx. The latter differs from the well known variety in having smaller foliage – the needlelike leaves are only 5-15 mm long and less than 2 mm wide, and has hairy flower stems. It is a more lower-growing plant, usually up to 25 cm tall with a prostrate habit. It is rare in cultivation, and originates from NW Africa and southern Spain.
All the major cultivars come from the species R. officinalis. There are three distinct forms of the species: Tall and upright – includes cultivars like Tuscan Blue, Miss Jessups Upright, Genge’s Gold, Portugese Pink, low and spreading – cultivars like Blue Lagoon, Collingwood Ingram, Lockwood de Forest, Rosea, Wendy’s White, Benenden Blue and the true prostrate ground covers – Santa Barbara, Huntingdon Carpet. There are also two cultivars, Blue Feather and Mason’s Finest that have very small foliage and are quite low growing. It is possible that these maybe cultivars of or hybrids with R. eriocalyx.
The upright forms tend to have large sticky leaves and a strong fragrance. The leaves strip easily and these plants make excellent hedges. They are often used for mazes. They are also popular for topiaries and as large pot plants for the verandah and court yard. They can reach up to 1.8m tall and 75cm wide. As they get older they have a tendency to ‘fall out’ and should be pruned annually in late spring. The spreading forms have a variety of shapes but are mostly around 0.75 to 1.2 m high and 1 to 1.2 m wide. They also respond well to an annual prune. They are excellent landscape plants due to their tolerance of a wide variety conditions and low water requirements. The prostrate forms are low growing to around 20cm tall and will hug the ground. They also cascade down over rocks and walls making them good for terraced gardens and large pots.
Rosemary flowers at a time when the delightful lipped flowers add a sparkle to a dull winter garden. They start flowering in mid winter and flower through to early spring. Some plants will repeat flower in mid autumn. The colors range from the deep blue of Tuscan Blue and Fota Blue, through light blue and silvery blue to pure white. There are also several pink forms that range form a soft mauve pink to the more solid pink of Portugese Pink. Each flower is attractive but the mass display on a large planting is quite stunning. With some varieties there are more flowers than leaves.
Rosemary has been cultivated since Roman times and is grown in all parts of the world. It performs very well in almost all parts of Australia. With the range of size, color and shapes there is a cultivar for every garden. Next month we will look at some of the cultivars and uses of this tough but attractive garden herb.