Alien
Invasion, Part 7:
Narrow-leaved Iceplant
Narrow-leaved
iceplant (Conicosia pugioniformis) is
a member of the plant family Aizoaceae (fig-marigolds). It is listed in the California Exotic Pest Plant
Council’s List A-2: “Most Invasive Wildland Pest Plants; Regional.” This weed is found on coastal dunes and in
sandy soils near the central coast of
Narrow-leaved
iceplant (Conicosia pugioniformis)
Conicosia
can be distinguished from other iceplant species by its bright yellow, hairy
blossoms and narrow, bright yellow-green leaves and branches. The common iceplant seen throughout coastal
Narrow-leaved
iceplant starts sprouting in the spring as a cluster of narrow, tubular,
succulent bright green spikes. The
plants can germinate from seeds or re-sprout from an existing taproot. The sprouting spikes eventually develop into
a basal rosette of succulent branches.
The leaves consist of alternate, linear, succulent spikes. Eventually, buds and flower heads
develop. Flowers consist of large (two
to three inch diameter) hairy yellow blossoms.
The flowers have an unpleasant odor.
The plant is low growing, never reaching more than about one foot in
height.
As
Conicosia matures and its flowers become fertilized, a conical green seedpod
forms under each blossom. Each pod has
from ten to twenty chambers, each with a smooth, spherical seed. In the late summer and fall, the plants dry
out, become woody and die. The seedpods
open and release the seeds. With over a
dozen blossoms occurring on each plant, it is easy to see how this weed can
multiply out of control in a short time.
Theoretically, each plant could produce hundreds of seeds for the next
generation of plants. Narrow-leaved
iceplant has spread throughout much of the
Mechanical
control of Conicosia is easiest by uprooting it when the plants are young and
have slender, hair-like taproots. The
plants can be left to desiccate on the surface.
However, each year an existing narrow-leaved iceplant will expand its
root system. After one or two years the
root can become large, over an inch in diameter. In such cases, the plants become very
difficult to destroy by mechanical pulling.
If severed near the surface, a taproot will re-sprout in the following
growing season. To prevent re-sprouting,
the root must be dug up, deep below the surface, or the plant must be treated
with a systemic herbicide. Another
problem with mechanical control is that uprooting may not control a plant that
has matured enough to form branches and buds.
There is enough moisture stored in the succulent plant that it may
continue to produce flowers that become fertilized and produce viable seeds. With more mature plants, removal from the
site or composting must accompany uprooting.
Herbicides
used on narrow-leaved iceplant may include systemic poisons such as Roundup.
No
biological controls (insects, etc.) are available at this time.