Abstract: A filament vegetation trimmer of the type wherein a stationary supply of filament is stored above the slinger head and fed out through a longitudinal feed passage for radial rotation with the slinger head is provided with an improved feed mechanism for selectively releasing incremental amounts of fresh filament from the storage site. The feed mechanism comprises a storage spool and indexer for permitting controlled quantities of the filament to be drawn from the spool under the centrifugal force exerted on the filament during operation. In the preferred embodiment, the feed control is deployed in an auxiliary handle and is configured to permit actuation by thumb pressure to enable an operator to release fresh filament without interruption of the trimming process.