FRIENDS OF EDGEWOOD NATURAL PRESERVE
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FRIENDS OF EDGEWOOD NATURAL PRESERVE
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INVASIVE EXOTICS - CONTROL EFFORTS SPRING 1996 By Ken Himes Above average rainfall this past winter brings promise of another good wild flower season at Edgewood County Park and Preserve. The downside is that the abundant moisture also contributes to vigorous growth of invasive exotics. Invasive exotics are plants not indigenous (not native) to Edgewood and are aggressively spreading into natural habitat. The Flora of Edgewood Park (Corelli, Revised 1994) lists about 26% of the species growing naturally at Edgewood as non-indigenous. They come from many sources and some remain restricted to earlier home sites such as daffodil and bearded iris. But others aren’t so benign. French broom, Genista monspessulana, a shrub with bright yellow flowers, has invaded portions of the park, especially along the lower Sylvan Loop Trail. Efforts by the Invasive Weed Eradication Group removed a large stand along the eastern portion of the Edgewood Trail. Return visits will be needed as seeds left behind can be viable for up to 25 years! These dormant seeds are part of what biologists call the seed bank, and removal of existing plants often makes for conditions that germinate some of these seeds. Current efforts are directed toward controlling Teasel, Dipsacus sativus (see Feb. 1995 Edgewood Explorer.) Great strides have been made in reducing the numbers of these invasive exotics. The eradication group is preparing to work on removal of two other invasive exotics in the coming months. These plants are: Italian Thistle, Carduus pycnocephalus, and Yellow Star Thistle, Centaurea solstitialis. Both are members of the aster family and have become widespread at Edgewood, except in areas of Serpentine substrate. Italian Thistle is an annual with spiny stems and leaves with small pink flower heads. It grows in a wide range of habitats. Small colonies - so far - can be found in grassland areas. It is also spreading into wooded areas along the Edgewood and Sylvan Trails. It blooms in May and June and seed forms soon after. The Invasive Weed Eradication Group will be patrolling trails to eradicate colonies in May. The key to limiting its spread is to prevent seed development.
Hand cutting or pulling and bagging the flowering plants was the method used last year. Several members of the eradication group, sponsored by Friends of Edgewood to go to the Exotic Pest Plant Council Symposium last October, learned that mowing can effectively manage infestations. Mowing should take place as the plant begins to flower, with a follow up in about four weeks. If you would like to help the Friends of Edgewood Invasive Weed Eradication Group control the spread of these invasive exotics, join Elly Hess on Friday mornings or Ken Himes Wednesday evenings at 5:30 at the Park and Ride. Special sessions will be arranged to remove Yellow Star Thistle in late June and July. Call Ken for information regarding these sessions. |
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Yellow Star Thistle is a particularly invasive plant that begins
flowering in late June and continues until October. It can be recognized by the 3/4 to 1
inch spines that surround the flower head. This plant was not intentionally introduced and
is listed as a noxious weed. It infests over 8,000,000 acres in California. It is not
known how long it has been present at Edgewood, but it has become widespread in the
non-serpentine grasslands and forms dense stands. Yellow Star Thistle was very abundant in
1995 and control efforts that year only removed small colonies outside of the major
infestation.