FRIENDS OF EDGEWOOD NATURAL PRESERVE

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By The Invasive Weed Eradication Committee, Elly Hess, Chairman

It's early on a sunny, warm Friday morning in May on Edgewood Natural Preserve in San Mateo County and Alice Musante lifts her mattock to about eye level, then swings it down at the base of a four-foot tall weed, knocking it to the ground. She has succeeded in decreasing the population of a very prolific plant called Teasel.

The Teasel that we have in Edgewood is Dipsacus sativus. It is not a native plant of California; its origin is Europe. Very few insects attack it here, so it thrives, especially in relatively moist ground. Fortunately, it does not grow on serpentinite soil. The plant is a biennial; however, in our temperate climate it often lives beyond its normal two-year life span. It is very drought-tolerant since it has a carrot-like root that remains in the ground all summer without drying out. Some of the roots are twelve inches long.

In the new Jepson Manual Dipsacus sativus has the common name of "Fuller's Teasel," while in most flower books Dipsacus fullonum carries the common name of "Fuller's Teasel."

Six years ago our small group of volunteers, under the direction of Elly Hess, began working in (then) Edgewood Park to see if we could reduce the number of Teasels. At that time there were thousands of healthy Teasels, primarily located in six separate areas in the west side of the Park.

When we first started our control programs we thought that, if we didn't allow all plants in any one area to re-seed, then, within two years, that area would be clear. We found, however, that at first our work seemed to have hardly any impact on the selected areas and the Teasel continued thriving. Apparently seed from prior years remains viable and continues to germinate over a period of three to five years. Our persistence in weeding Teasel-infested areas year after year only started paying off about the fifth year.

We believe we now, finally, have that weed under control. There will always be a few new plants that sprout each year but these are easily removed.

Our method of controlling Teasel is as follows:

1. In early spring when the new plants can be easily pulled from wet ground, we spade them out one-by-one. In this way we remove the root from the soil and know that we have definitely reduced the weed population by one. We realize that we are disturbing the soil when we spade, and are probably giving older seed in the soil the opportunity of germinating with the next fall rain. However, we feel the advantage of removing a large plant outweighs the chance of allowing some small plants to sprout the next year.
2. When the ground dries so that it becomes difficult to dig out the roots, we shift to light-weight mattocks and cut off the crowns of plants just below the soil surface. At this point the seed heads have not yet matured.
3. After seed heads mature, we carefully cut off each head and place it in a bucket. Hundreds of seeds spill out into the bucket at this time. When the bucket is full, its contents are dumped into a large plastic bag. When the bags are full of seed heads, they are tied at the top and put in a spot where they can be picked up and removed from the property by a park ranger.
4. About six weeks after the dead-heading operation, we make a sweep of all the areas we have previously cleared. Any Teasels that we find at that time are disposed of.

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