Culinary and Aromatic Herbs
By Joe-Ann McCoy, Ph.D. candidate
1999 has been dubbed the "Year of Lavender"; as a result there will be an increased demand for information and literature concerning all aspects associated with lavender production. The following information has been compiled from a recent literature review, which will hopefully provide helpful information sources to the interested grower. Any individual interested in lavender production needs to understand the complicated taxonomy of Lavendula species before attempting to choose a cultivar. There are also various questions to address when choosing a variety, such as whether the plant is being chosen for essential oil production, cut flower production, or dried ornamental use. An important aspect of propagation for essential oil production is an understanding of the phytochemistry associated with the lavender varieties.
"Mercury owns the herb and it carries his effects very potently." (Culpeper, 1652)
Uses: Aromatic, carminative, antispasmodic, expectorant, stimulant, cosmetic, culinary, decorative, medicinal, antibacterial, and antiseptic
The traditional uses of lavender range from use as a perfume to a antimicrobial agent. This powerful and potent herb has been utilized throughout antiquity and is still retained as a common household ingredient today. Recent studies have found that essential oils from this extraordinary species can replace chemical methods currently in use to suppress sprouting in potato tubers for storage (Vokou, 1993). In bioactivity studies in India, lavendula species have been proven to show potent activity against insect pests (Sharma et al., 1992). Another study in Austria provided evidence of the sedative effects of the essential oil of lavender after inhalation (Buchbauer et al., 1992). Currently, the majority of lavender products are utilized for essential oil production and for their aromatic properties.
The Greek naturalist, Dioscorides, praised the medicinal attributes of Lavender in the first century A.D. In ancient Egypt it was used as a perfume and as an essential ingredient for incense. Lavender was a favorite ingredient in herbal baths of both Greeks and Romans. During the Middle ages it was considered an herb of love and was used as an aphrodisiac. It was also believed that a sprinkle of lavender water on the head of a loved one would keep the wearer chaste. Due to its insecticidal properties, lavender was strewn over floors in castles and sickrooms as a disinfectant and deodorant. Lavender was used as an ingredient in smelling salts and was used to disinfect wounds during wartime. It was used as an insecticide to protect linens from moths. In China, Lavender is used in a cure-all medicinal oil called White Flower Oil. Other historical uses include embalming corpses, curing animals of lice, taming lions and tigers, repelling mosquitoes, snuff flavoring, and as an ingredient in special lacquers and varnishes. Culinary uses include flavoring vinegars, jellies, and salads. Medicinal uses include treatment of headache, hysteria, nervous palpitations, hoarseness, palsy, toothaches, sore joints, apoplexy, colic, coughs, and rumbling digestive systems.
Roman superstition persisted that the asp (a dangerous viper) made his nest in lavender bushes which drove up the price of the plant and made it necessary to approach it with caution.
Culpeper (1652) suggests, "two spoonfuls of the distilled water of the flowers taken helpeth them that have lost their voice; as also the tremblings and passions of the heart, and faintings and swounings"
Salmon suggests (Herbal, 1710) that "it is also good against the bitings of serpents, mad-dogs and other venomous creature, being given inwardly and applied poultice-wise to the parts wounded. The spirituous tincture of the dried leaves or seeds, if prudently given, cures hysterik fits though vehement and of long standing."
FAMILY: Labiatae (Lamiaceae) (Mint)
Lavender species of commercial importance are native to the mountainous regions of the countries bordering the western half of the Mediterranean region of Europe. The name "lavender" comes from the Latin verb lavare "to wash" or "to bathe." There are approximately 20 species of lavender with hundreds of various genotypes differentiated by variations ranging from growth form to chemical composition of essential oil.
Culpeper (1652) in his book, The English Physitian, wrote for his description of lavender simply, "This is so well known, being an Inhabitant in almost every Garden, that it needeth no Description."
English Lavender, Lavendula angustifolia, is the most widely cultivated species (synonyms - L. vera, L. latifola, L. officinalis, L. spica, L. delphinensis). The common narrow-leafed variety grows 1-3 ft high with a short but irregular crooked, much-branched stem, covered with a yellowish-gray bark, which comes off in flakes and very numerous erect straight, broom-like, slender, bluntly quadrangular branches, finely pubescent with stellate hairs. The leaves are opposite, sessile, entire, blunt and linear or lance-shaped. When young, leaves are white with dense stellate hairs on both surfaces with strongly revolute margins. When full grown, leaves become greener and extend up to 2 1/2 in long, with scattered hairs above, smooth or finely downy beneath, with the margins only slightly revolute. Flowers are produced in terminating one-half-inch-long spikes from the young shoots, on long stems. The spikes are composed of whorls or rings of flowers, each composed of six to ten flowers; the lower whorls becoming more distant from each other. The flowers themselves are very shortly stalked, three to five together in the axils of rhomboidal, brown, thin, dry bracts. Leaflike bracts are in an opposite arrangement below each whorl. They are usually shorter than the calyces. According to Tucker and Hensen (1985) lavenders can be distinguished by their bracts; those of L. angustifolia are ovate-rhombic in outline, with a length/width ratio of 0.83 to 2.20 with bracteoles absent or up to 2.5 mm long. The calyx is tubular and ribbed, with thirteen veins, purple-gray in color, five-toothed and hairy with shiny oil glands among the hairs visible with a hand lens. The majority of the oil extracted from the flowers is contained in the glands on the calyx. The 2-lipped corolla is a bluish-violet color. Flowering is generally from mid to late June to early July.
There are many cultivars of English Lavender including the white dwarf Nana Alba, also pink varieties designated Rosea, Jean Davis, and Lodden Pink, which may be the same cultivar. Cultivars with dark flowers include Twickle Purple, Dwarf Blue, Hidcote, Royal Purple, Loddon Blue, Middachten Nana Atropurperea, Mitcham Cray, Munstead, and Summerland Supreme. Lavender-blue flowered cultivars include Backhouse Purple, Bowles Early, Compacta, Folgate, Graves, Gray Lady, Gwendolyn Anley, Irene Doyle, and Maillette.
Of the various blue cultivars, Irene Doyle (Tucker, 1984) is considered unique in its ability to flower twice. Its excellent fragrance and concentrations of essential oil make it suitable for commercial harvest. 'Irene Doyle' was the first recurrent-blooming lavender discovered by Thomas Debaggio of Earth Works Nursery in Arlington VA. Other recurrent bloomers introduced by Debaggio are 'W. G. Doyle', which he calls dark supreme lavender, and 'Susan Belsinger.'
Another cultivar, L. Lady, was the 1994 winner of the All-American Selection. Its unique attributes include that it germinates quickly (14-28 days; 78% germination), it comes true from seed, and blooms the first year (south- 3 months; north- 5-6 months). This cultivar was developed by the late Ted Torrey, head plant breeder for W. Atlee Burpee & Company.
Lavandin, Lavendula. x intermedia (syn. L. hybrida) is an interspecific hybrid between L. angustifolia and L. latifola and has intermediate characteristics (angustifolia = narrow; latifola = broad). Lavandin is a sterile hybrid and must be vegetatively propagated. It has ovate-rhombic bracts like English lavender but the width to length ratio is 1.33 to 3.00 and bracteoles are always 1-4 mm long. Both leaf size and plant height (3 ft) are larger in lavandin when compared to English lavender. Typically, lavandin varieties bloom 3-4 weeks later than English lavender and have significantly higher essential oil concentrations. It is widely cultivated for nursery production and also grown commercially as a source of essential oil. Commercial lavandin oil- and flower- producing cultivars include, Grosso, Abrialii, Super, Standard, Maime Epis. Horticultural cultivars include Dutch, Grappenhall, Hidcote Giant, Old English, Provence, Seal, and Silver Gray.
L. latifolia, or Spike Lavender, is one of the species that makes up the lavandin hybrid but is not hardy, being a native of the Mediterranean. It is grown primarily for its essential oil and is rare in the U.S. It can reach 3 feet in height and spread.
L. lanata, wooly lavander, is an exceptional potpourri plant because of its balsam-lavender fragrance. This plant is a 2-3 foot shrub with fragrant, lilac-colored spikes blooming in midsummer.
L. heterophylla, grows up to 4 feet in height and is suitable for growing in containers. It is characterized by its irregularly shaped, toothed leaves and unusual gray-green foliage.
French lavender or Fringed lavender (Lavendula dentata) grows up to three feet in height. Leaves are 1 1/4 inch long; linear-oblong with rounded teeth at margins, grayish in color and covered with soft fuzz. The spikes are up to 1 3/4-inch long and 1/2 inch diameter. The 1/4 inch wide, purple, oblong to oval-shaped bracts are up to 1/2 inch in length with 3/8-inch dark purple flowers. This species grows in Spain and warm temperate regions. It is generally treated as an annual and grown as an ornamental. This species is grown for its rosemary-scented flowers and for potpourri production.
L. stoechas, Spanish lavender, is a woody shrub growing to four feet tall with linear to oblong, lance shaped leaves about 3/4 inch diameter with 3/8 inch, dark purple flowers. Its elegant flowers are often used for dried flower production. Spanish lavenders tolerate more acid soils than other lavenders but are not hardy and need to be treated as annuals and are generally grown as ornamentals.
L. multifida, (fern-leaf lavender), L. pinnata, and L. canariensis are characterized by their lacy, finely divided fern-like leaves with solitary spikes in threes (trident-form). All three adapt well to container growing but are not widely cultivated in the U.S.
L. canariensis, native to the Canary Islands, has feathery foliage with dark-blue flower spikes with a turpentine scent. According to Tom DeBaggio, it self sows so prolifically that it can be treated as an annual.
A hybrid cross between L. dentata and L. latifolia, is known as Lavandula x allardii, or giant lavender. It can reach 5 feet in height and 4 feet in spread with indented or scalloped leaves and very large violet-purple flower heads. L. Sawyers, is another hybrid (L. angustifolia and L. lanata) which is considered half-hardy. It is characterized by large gray leaves with flowers ranging from lavender-blue to deep purple. Its flowers are dried for crafting and for use in potpourri.
Lavender oil contains up to 40% linalyl acetate and 30% linalol. Linalol is a terpene alcohol that is non-toxic to humans, yet naturally antimicrobial. Linalyl acetate, its acetic ester, has a pleasant, sweet, fruity, aroma which along with its antimicrobial properties makes lavender unique. Other constituents of the oil are cineol, pinene, limonene, geraniol, borneol and some tannin. Lavender oil is soluble in all proportions of alcohol. There are two esters in the oil which are the primary source for the odor of lavender. Of these the principal is linalyl acetate and the second in linalyl butyrate. Various cultural practices can effect the ester value of Lavender oil. These include choice of cultivar, use of soil amendments, how and when flowers are gathered (optimal when flowers are fully expanded), how quickly the harvest is distilled, and how it is distilled (steam distillation is better than water).
L. angustifolia oil contains linalyl acetate (up to 40%), linalool (~25%), geraniol and its esters. L. latifolia oil has alpha-pinene, camphene, beta-pinene, sabinene, betamyrcene, 1,8-cineole (up to 33%), beta-cymene, linaloyl oxide, camphor (~5%), and linalool (up to 25%), among other constituents. L. stoechas oil is high in camphor (24-72 %), borneol, cineole, fenchone, (up to 34%), linalool acetate, and others. L. angustifolia, L. x intermedia, L. latifolia, and L. stoeches all contain the antioxidant rosmarinic acid (Foster, 1993).
When choosing a lavender cultivar the first decision is to distinguish between use for essential oil production, cut flower production, or ornamental use. Commercial uses can include essential oil production, cosmetic manufacturing, sale to restaurants (salads, food flavorings), sachets, tea, potpourri, soaps, or sale of ornamental plants. Lavandin varieties (Lavendula x. intermedia) produce both the highest yields of flowers and highest concentrations of essential oil per acre. Lavandins produce large, long stemmed flowers which are slightly gray in color while English lavender (Lavendula angustifolia) varieties produce shorter-stemmed flowers with a blue color when dried. English lavender varieties are better suited for dried flower production than Lavandin varieties.
For commercial production it is strongly recommended to set up trial areas of approximately 200 plants each with selected cultivars to determine quality and yields before planting on a large scale. There are early, mid, and late season flowering varieties available. Lavender grows best in light soil, sand, or gravel, in a dry, open and sunny position. It requires good drainage and prefers a warm, well-drained loam with a slope to the south or southwest. Lavender varieties are susceptible to frost injury. English lavender varieties prefer chalky soils, whereas the lavandin varieties require slightly more acidic soils. Thomas DeBaggio of DeBaggio Herbs in Arlington, VA, has reported that lavenders develop optimally with 33 inches of annual rainfall. According to Jim Duke, (retired botanist, USDA) annual rainfall can range from 12-54 inches per year for lavender cultivation (Foster, 1993).
SEEDS. Propagation by seed is slow (six months to transplant size) and germination rates are low and sporadic. In addition, because most lavender varieties are clones, vegetative propagation (cuttings, layerings, and division of roots) is highly recommended to retain desirable traits. Propagation by seed creates overlapping traits and further variation within cultivars. Plants grown from seed are variable in growth habit, color, and essential oil composition and are unsuitable for commercial harvesting. If seeds are to be used they should be planted in late spring or early summer. Plants should be thinned to 24-36 inches apart with rows 30 to 36 inches apart.
CUTTINGS. Lavender is mainly propagated by cuttings, layering, and division of roots. Because many lavender varieties are not winter hardy and some exhibit poor rooting ability, careful choice of cultivar is recommended.
In a study in Europe (Boyadzhieva et al., 1977), optimal rooting was achieved with 8-10 cm long cuttings from 1-year-old plantings set in open beds in October and November.
Closer to home Thomas DeBaggio successfully propagates lavender from stem tip cuttings. He suggests taking 4" cuttings from disease free plant material in spring when buds are beginning to form. He nips the buds and removes all leaves from the bottom half of the cuttings. Cuttings are placed in a soil medium composed of one part perlite and one part peat moss (11x21x2 1/2-inch plastic flats which hold 100-300 cuttings). Bottom heat (75-80°F) increases the rooting of lavender tip cuttings a great deal along with a light feeding every two days. High light (12-14 hrs/day) and ventilation (fans) is required for optimal germination. Under these conditions root growth is achieved by 14 days. Cuttings are then planted in 2.5 inch pots, pinched, and produce marketable plants in 6-8 weeks.
In contrast, Dr. Art Tucker, of the University of Delaware, advises taking cuttings in the fall before the first freeze (August-Nov.) when stems are semi-hardened. He recommends a mix of one part coarse perlite to one part sterilized, baked clay frit (cat litter). Cuttings are placed in trays being careful not to allow leaves to touch soil surfaces, which can result in burning the leaves. Uncovered flats are placed in a partially shaded greenhouse for propagation. Slow growth rates should be expected in the first year (6-8 in). Dr. Tucker reports a 95-100% success rate with this method.
In the book "A Modern Herbal" published in 1931, Mrs. M. Grieve suggests taking cuttings from young wood in fall or spring by pulling a healthy branch downward so that a piece of the older wood (heel) is retained. These cuttings are placed in moist sandy soil in a shaded cold frame or in pots with lath protection. Plants should be pinched back during the first year to avoid blooming so that the plant can put all of its energy into forming roots and lateral shoots. She recommends protecting plants from both summer and winter winds to prevent damage to the spikes.
LAYERING. This is the simplest method of propagation, although the least efficient in terms of time and number of regenerants per plant. Woody herbs propagate by layering naturally when trailing branches grow close to the soil surface and send down roots, which create new plantlets. To propagate by layering, select a long, healthy flexible stem and remove 4-6 inches of foliage, leaving 3-4 inches of foliage at the tip of the branch. Pile up 2-3 inches of bark under the stem section and make a shallow depression in the top of the pile. Press the stem into the indention and cover the bare section with moist soil or a sphagnum moss and perlite combination. A U-shaped piece of wire can be used to hold the stem section firmly in place. Keep rooting sections moist and expect transferable plants within 2 weeks to 2 months depending on environmental conditions (Oliver, 1996). Once rooted, cut the new plants from the mother plants and transfer to individual pots.
TISSUE CULTURE. Tissue culture (syn., in vitro culture, micropropagation) methods have been developed for the mass propagation of lavender varieties from hybrid stock plants. Tissue culture regenerants can produce disease-free, genetically identical plants from parent plants exhibiting desirable traits. Tissue culture protocols are generally cost prohibitive to small-scale growers because of the specialized sterile laboratory equipment required. Tissue culture propagated plants can be purchased, however.
FIELD CULTURE. Plant all species in a protected south facing location with well-drained soil within a pH range of 6.4-8.3. Prepare the site by mixing compost or peat moss with the top four inches of soil and preparing a raised bed. If a good cover crop had been grown or manure was added to the field before planting, fertilization may not be necessary for several years. Young plants should be set out in early spring in rows 2 feet apart with one foot spacing between plants. Another method of spacing is to plant 18 inches apart each way for the first year of growth, then to remove every other plant in the second year resulting in 36 inch spacing which produces optimal flower and essential oil yields. Removed plants are divided into approximately 3 plants each and replanted in new rows. DeBaggio recommends fertilizing every three weeks during the first year of growth and irrigating once a week during dry periods. Any dead leaves or stems should be snipped off throughout the growing season. In mid-April, DeBaggio prunes field-grown established plants heavily by removing 1/3 to 1/2 of the stem length all over the plant. This heavy pruning stimulates growth from the base of the plant. A thick layer of mulch is recommended after the first frost.
In order to discourage fungal pathogens, good air circulation is advised and can be achieved by spacing plants 2-3 feet apart and trimming the lower branches throughout the growing season. Avoid heavy organic mulches (sawdust, wood chips) as they can increase both fungal pathogens and insect problems.
Commercial lavender plantations are usually established by planting in single rows spaced appropriately to allow tractor access. As plants die they are removed and replaced with healthy stock.
Hardiest plants are English lavender (L. angustifolia), Lavandin (L. x intermedia) and spike lavender (L. spica, or L. latifolia). English lavenders grow poorly in the hot, humid southeast, while lavandins can grow and thrive as far south as Florida.
The most common disease problem with lavender is wilt. Vascular wilts are very destructive diseases with typical symptoms characterized by rapid wilting, browning, and dying of leaves and succulent shoots of plants followed by the death of the plant. English lavender varieties are more susceptible to vascular wilts than lavendin varieties. Dark-flowered cultivars are less resistant to disease than the pale-flowered varieties. Cultivars with gray foliage are quite susceptible to infection. Vascular wilts are most common in the month of August when temperatures reach 90° F and humidity reaches 90%. If damaged plants are present, remove and destroy any infected plant material and avoid replanting with susceptible varieties. Dr. A. O. Tucker advises using one to two inches of white sand as a mulch around plants to reduce fungal pathogen infection. In addition, he found that the sand increased flower and oil production when compared to a control group of plants which were not mulched.
Pathogens associated with lavender:
Few insect problems have been reported on field-grown lavender. A defoliating moth larva has been reported in Australia.
Weed control is especially important during the first two years of growth as the plants become established. Mechanical cultivation and use of mulch are the primary methods of control.
English lavender (L. angustifolia) cultivars are best for dried flower purposes because the flowers persist on the stems when dry, whereas Lavandin cultivars are easily separated from the stem and are better suited for essential oil and potpourri purposes.
A crop harvested for dried flower purposes should be harvested when the first few florets are open. Flower stalks are cut just under the first pair of leaves. Essential oils are accumulated in the flowers and flower stalks. Flowers for oil production are harvested when at about 50% blooming. For optimal ester levels, flowers are harvested starting in the second year between early blossom and maximum bloom stages early in the day before full sun conditions. Lavender is 70-80% water and takes 7 to 14 days to dry. Prices can range from $10 to $15 per pound.
Plants are harvested from the second through
the fifth year at which time some growers replant.
Others report that plants may be harvested
up to 30 years. Lavender is harvested mechanically
in foreign countries using specially designed
machinery for essential oil purposes although
it is harvested by hand for cut flower production.
|Location||English Lavender (L. angustifolia)||Lavandin (L. x. intermedia)|
|Bridgestowe Estates, Australia (1998)||N/A||4,000 lb/acre fresh flower
53 lb/acre essential oil
|Foster (1984)||300-1,800 lb/acre fresh
12-15 lb/acre essential oil
|3,500-4,500 lb/acre fresh
53-67 lb/acre essential oil
|Douglas (1991)||30 gal/acre essential oil||50 gal/acre essential oil|
|Sturdivant & Blakley (1999)||150-200 lb/acre dry flower||250-300 lb/acre dry flower|
Redbank Research Center, New Zealand
|2.6 gal/acre essential oil
12,000 dried bunches/acre
1 bunch = 3.5 oz
|14.7 gal/acre essential
16,000 dried bunches/acre
1 bunch = 3.5 oz
In a study from the Egyptian Journal of Horticulture, optimal yields of aerial parts of lavender were observed following fertilization with urea at 88 lb./ acre. The best yields of essential oil were observed following application of ammonium chloride (N source) at 44 lb/ acre (El-Sherbany et al. 1997).
In a germination study of lavender seeds, the effects of giberellic acid, light/dark regimes, and pre-freezing were studied. It was determined that the giberellic treatments, with or without pre-freezing, significantly increased the percentage of germination and accelerated overall germination rates (Aoyama, 1996).
The positive influence of foliar applications of sulfur (1%) and phosphorus (1%) on the yields, volatile oil and minerals of lavender was studied during 2 successive seasons in Egypt. Foliar applications had positive effects on plant height (P 1%) and dry weight (S 1% + P 1%) of herb. The maximum value of essential oil was obtained with S as a 1% foliar application (Hussein et al., 1996).
Raev et al. (1996) found that polyploidy could be induced in L. angusitfolia cultivars to obtain new productive varieties.
Preliminary testing was performed on lavender field crops to test a prototype machine designed to control weeds by flaming. The machine was mounted on a trailer and the crop rows were protected by lateral bulkheads. The results indicated that flaming with this machine significantly reduced weeds but that the lavender plants were susceptible to damage if sufficient care was not taken (Martini, 1996).
Current research from the Netherlands has proven that essential oils of Lavendula angustifliasuppress sprouting in potato tubers and are also antimicrobial. This produces a safe. non-chemical method to store potatoes and at the same time prevent microbial attack (Vokou, 1993).
The bioactivity of lavendula species against insects in India proved that the majority of the plants studied showed activity against insect pests (Sharma et al., 1992).
In a 1992 study on the micropropagation of Lavenders and Lavandins, a tissue culture protocol was established for the mass propagation of disease free plantlets from commercial hybrid stock plants. When regenerants were planted in fields, quality characteristics, including essential oil concentrations, were similar to parent plants. Tissue cultured plantlets could therefore be a good source of disease-free plantlets for regeneration purposes (Chambdon, 1992).
An Austrian study provided evidence of sedative effects of the essential oil of lavender after inhalation. (Buchbauer et al. 1991). They proved through experimentation with mice that the essential oil of lavender did indeed facilitate falling asleep and a minimization of stressful situations.
In a study on the vegetative propagation of lavender by rooting of stem sections, 1 year old wood, various mixed wood, and three-year-old wood stem sections were compared. The highest percentage of rooting was obtained from 8-10 cm long, 1-year-old cuttings in open beds in October-November (Boyadzhieva et al., 1977).
Researchers in Bulgaria have experimented with the reconstruction of lavender planting to wide-row spacing in regard to mechanized cultivation and harvest (Tsachev, 1976).
A comparison of three French varieties of lavender for optimal essential oil concentrations showed that 'Superb' and 'Abrial' varieties had higher flower and essential oil yields per ha than the 'Normal' variety (Chingova et al. 1973).
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Dr. Jeanine Davis
Maintained by: Bryan A. Konsler
Format updated October 22, 2007