Archive for the ‘Botany for Gardeners’ Category

Wednesday, August 27, 2008

The Last of the Thistles

Carlina acaulis growing in Bonnefont Garden.

Since we have received appreciations from so many thistle lovers, I thought I would finish out the series with the carline thistles, the last thistles in our medieval plant collection to bloom. Unlike other thistles, their flowers have a daisy form consisting of a disk with rayed petals. They are dry flowers of the “ever-lasting” type, sometimes described as straw flowers. The carline thistles are plants of poor, dry soils. The U.S.D.A. lists the common carline thistle, Carlina vulgaris, as an invasive weed reported in New York and New Jersey, but no other state, although I have never observed them in either. Has anyone seen it in their locale? (The U.S.D.A. site notes that it is not necessarily the case that a plant is established only in the states indicated by shading on their map. It may well grow elsewhere, but its presence has not been reported to the U.S.D.A.)

The perennial stemless species, Carlina acaulis, native to Europe, strongly resembles the closely related Eurasian biennial Carlina vulgaris, except that the rosette of spiny leaves lies close to the ground, while the common carline thistle has a short stem. The leaves of C. acaulis are also longer than those of C. vulgaris. Read more »

Thursday, August 7, 2008

Weed Control

Anagalis arvensis is a weed that produces an advanced root system to ensure its survival. Datura stramonium relies primarily on seed for reproduction.

Left: Anagallis arvensis, a weed that produces an advanced root system to ensure its survival; right: Datura stramonium, a vigorous weed that relies primarily on seed for reproduction.

A weed is defined in the most simple manner as a plant growing in an area where it is unwanted. This could apply to a garden, a farm, or any possible landscape where a plant may appear. Plants may be considered unwanted based on ornamental value or their competitiveness with desired plants. Plants within the same community often compete for water, nutrients, and physical space. Unfortunately, it is the weed that most often wins, followed by a reduction in crop yields and garden aesthetics. It is in these situations, that weed control is most often practiced. Read more »

Friday, July 18, 2008

The Thistle Tribe

Cotton thistle flourishing in Bonnefont Garden. The leaves of the cotton thistle are thickly felted with white down.

The most imposing of the several thistles we cultivate at The Cloisters, the stately cotton thistle has a presence that appeals to modern sensibilities. The silvery-white leaves are deeply cut and very handsome: the species name acanthium denotes their resemblance to the foliage of the acanthus. Some value cotton thistle as an ornamental in contemporary gardens, although others consider Onorpordum acanthium to be a weed. (A weed is a plant you don’t want, while an herb is a plant with a use. Many of the plants we grow in the gardens of The Cloisters are considered weeds in our time and place, but were herbs in the Middle Ages.) Once the purplish-pink flowers of the cotton thistle have withered, it is important to remove the heads so that the many seeds do not disperse to the four winds and colonize the world. Read more »

Thursday, July 10, 2008

The Fragrance of Lavender

True or English Lavender (L. angustifolia subspecies angustifolia growing in Bonnefont Herb Garden.

Above: Lavandula angustifolia in Bonnefont Cloister Herb Garden

The scent of lavender has always represented the quintessential fragrance of the herb garden to me. This sweet, full-bodied aroma has the magical ability to conjure up special memories and associations with the past and present. Although this fragrance may seem magical, it also serves a very important biological function for the plant and the ecosystem in which it exists. The aroma of the flower attracts insects that share a symbiotic relationship with the plant. Bees—the most important of these insects—are integral in the pollination of lavender. They serve as pollen vectors between male and female flower parts.

Read more »