– Cornflower, Knapweed.
Colours and heights various.
A race of hardy and easily grown plants for the
perennial border. They are not fastidious as to
soil, but should have a well-dug site and open
exposure. Pieces of the root should be planted
in autumn or early spring, and may stand for three
years, when the clumps should be divided and replanted
in a fresh place. The following are the best kinds:
• Centaurea Babylonica. A very ornamental plant
with silvery foliage and yellow flowers. It requires
plenty of space, and in good soil will reach a
height of ten feet.
• Centaurea macrocephala. 3 to 4 feet; flowers
in July, strong orange, in shape like those of
a thistle, or the typical “knapweed”
or “hardhead” of the meadows.
• Centaurea Montana. The Perennial Cornflowers,
a well-known and very effective family. The flowers
resemble those of the Cyanus or annual Cornflower,
but are much larger. There are varieties in several
distinct colours besides the original blue; alba,
a fine white; rubra, a light crimson; sulphurea,
a very pale sulphur or cream; and purpurea, a
blue-violet. The crimson and purple shades are
apt to be a little dull and ineffective, but all
the Montana section are free-growing and need
little care, and deserve a place in any border.
Besides the perennial Centaureas there are two
or three half-hardy sorts, chiefly used in bedding-out
for the sake of their foliage. The best of these
are candidissima (called also Ragusina) and gymnocarpa.
Both have silvery foliage, and grow about a foot
high. They should be raised from seed sown in
moderate heat in March, grown on with the routine
proper for half-hardy perennials, and planted
out at the end of May.
The annual Cornflower and the Sweet Sultan (both
of the Centaurea family) are described under their
See also Cornflower