April 2005

The most commonly grown and marketed species is Scutellaria lateriflora, variously called American Skullcap, Virginia Skullcap, Mad Dog Skullcap, or Blue Skullcap.  Only the flowering tops are used for medicinal purposes.  The plant is similar in appearance to Marsh Skullcap, but has flowers only 6-10 mm long; these all face the same direction.  This species was used by the Cherokee Indians, and in 1772 was thought to be useful in treating rabies, thus the name Mad Dog Skullcap.  It was later considered valuable as a sedative and antispasmodic.  More recently it has had uses in weaning patients from barbiturates and tranquilizers.  It has been reported that another European species, Tall Skullcap (S. altissima), larger and with showier flowers, has been propagated by American nurseries and mislabeled as S. lateriflora.  Tall skullcap has escaped cultivation in Massachusetts. 

Another cultivated species that can be grown in Saskatchewan is Scutellaria baicalensis, Baical Skullcap, from the Lake Baikal region of Siberia, as well as China.  In China, it is known as Huang Qin, although that name may be applied to other species as well. The roots of this plant are marketed, but it may be in less demand in North America than the former species.  It has been used in ancient Chinese medicinal practice up until the present.  It contains flavonoids that are considered valuable for improving liver function, and for anti-inflammatory and anti-allergenic effects.  Normally the plants are grown three to four years before being harvested.  This species may also have some value as a garden ornamental.  The plant grows to 45 cm, with a spreading habit; leaves are lanceolate, obtuse, entire, and ciliate, with blue or bluish-purple flowers.  It has performed well in the Saskatoon, Outlook and Prince Albert areas.

The native Marsh Skullcap is widespread in the Parklands region, and is found in northern Canada and Alaska, and other northern countries. It is a perennial herb growing 30-60 cm tall, with ovate-oblong, very short stalked leaves 2-6 cm long, with blunt teeth.  The tubular flowers are 12-20 mm long, blue or pink-purple, and streaked with white. The sepals are fused into two small lips, with a raised bump on the upper lip.  The flowers are borne singly or in pairs in the leaf axils of the stem.  This species is also known as European Skullcap.  It is most likely to be found in moist places and along streambanks and roadside ditches.  This species is reported to have similar constituents to Baical Skullcap, but is used as a substitute for American Skullcap. 

There are many other species of skullcap, some of which have been used medicinally, especially in Asia.  Most of the medicinal Asian species have not been cultivated in North America, but recently Scutellaria barbata, Barbed Skullcap has become available. In China, that species is known as Ban Zhi Lian. There are also various ornamental species.   

Considerable controversy has existed in the past over the use of skullcap.  Although it was used in North America in the 18^th and 19^th Centuries, there were suggestions as early as 1830 that skullcap was useless, and in 1946 the U.S. Dispensatory declared it destitute of medicinal properties.  Nevertheless, it has remained in folk medicine and seems to be gaining some recognition again.  To compound the problem, some toxic effects were attributed to this herb in the past.  It is now known that an adulterant, germander, is the likely culprit.   Recent clinical trials in China have suggested that there are valid uses for Baikal skullcap, but its use in North American is still limited.   

Propagation

Formal research on agronomic practices has not been conducted in Saskatchewan, but the crop has been successfully grown on some farms.  Skullcap is usually grown from seed or transplants.   Divisions or cuttings are also possible, although the latter is less reliable.  Because Baical skullcap is less easily transplanted, it may be desirable to direct sow this species, whereas American Skullcap is easily transplanted.  Suggested direct/(indirect) seeding rates are 1.1.5 (0.1-1 kg) kg/ha for American Skullcap and  8-12 (0.3 – 2 kg) kg/ha for Baical Skullcap.  As seedlings, the plants are prone to overwatering and spider mites.

Skullcap will grow in full sun to partial shade.  Light shade may be desirable where moisture is lacking, but for best production ample moisture is desirable.  Of the two common species, Baikal skullcap is more drought tolerant.  Skullcap is generally irrigated as lack of moisture is considered a limiting factor in production.

The fertility requirements for skullcap are not well documented, but it is desirable to have good fertility, and supplemental nitrogen may be desirable once production begins.  As the plants are perennial, a site should be chosen that can hold the plants for three or four years. A light, well-drained soil is desirable, particularly for Baical Skullcap.

Suggested field spacing is 15-30 cm between plants, with rows spacings of up to 60 cm.  An alternative is to grow the plants if beds up to 90 cm wide.  Prior to planting, it is important that the field be relatively weed-free, particularly of perennial weeds.

No serious diseases or pests have been documented for established skullcap crops in North America. Greenhouse grown plugs may be susceptible to tomato spotted wilt virus or impatiens necrotic spot virus, both transmitted by thrips. Leaf beetles have been noted in a few countries.  Where drainage is poor, root rots (Pythium or Phytophthora) may attack Baical skullcap.  Powdery mildew is a potential problem for native species.

American Skullcap is cut when it begins to flower, although some suggest harvesting in the late flowering period when seed pods are present.  A second cutting can be made in the fall.  As the plants are cut, the tops should be piled thinly in a shaded location.  It is important that the harvested material not be allowed to heat up after harvesting.  According to research in Australia, compaction of product can reduce the flavonoid levels. The tops will dry quickly in three to five days if turned frequently. Alternatively, hot air dryers can be used for quick drying, with temperatures up to 70°C considered acceptable for American Skullcap. Full color after drying is demanded by many buyers. Buyers may also request documentation for the presence of scutellarin in American Skullcap and baicalin in Baical Skullcap.  Some may request documentation for other flavonoids. If it is to be shipped fresh, product should be picked early in the morning while it is cool, and shipped as soon as possible.  Fresh product can be used in infusions, liquid extracts and tinctures, while dried product can be made into tablets or capsules. 

Baical Skullcap is harvested in spring or fall, with roots being dug of three or four year old plants.  The tops of this species are discarded and the roots are generally dried.  It is often combined with other herbs in traditional Chinese medicine.

Barbed Skullcap  may be harvested as whole plants and dried.  It contains both alkaloids and flavonoids.

Little information is available on storage limitations, but it is known that dried skullcap product (American) stored between 5 - 30°C at ambient humidity gradually loses quality (loss of flavonoids), with more serious losses if the product reabsorbs moisture. Experimental long term storage of extracts indicated that flavonoid losses occurred at twice the rate of dried product.

Many herb crops in Saskatchewan are grown organically, and this crop should adapt easily to organic production methods.

In recent years, certified organic prices have been in the range of $8-15/lb (17-33/kg) whereas conventional prices have ranged from $2-9/lb (4.40 -19.80/kg).

As with all herb crops, a market should be determined before planting skullcap on a large scale.   Markets outside of Saskatchewan will likely need to be secured.