Preventing Plugged Tile Drains Under Stream Buffers

Some species of trees, shrubs and grasses can plug perforated tile drains with roots. Perforated tiles are 'collector tiles' which means the tiles are full of holes. The small holes allow excess soil water to enter into the tile and flow out of the field usually to a drainage ditch or a stream. Perforated field tiles improve the rooting zone of the crop and improve crop yield, or health of orchards and vineyards, by controlling the water table to the depth of the tile. The tiny perforations in tile are necessary for water removal but unfortunately will also allow roots of vegetation to grow into the pipe and plug it.

Vegetation that is known to give most trouble at plugging tile with roots includes plant species that have aggressive root systems, which naturally prefer wet or saturated soil. Poplar, willow, soft maple, eastern white cedar and horsetail weeds are a few examples of wet-site species that are known to be problematic near perforated tile drains.

Wet-site plant species are most common along vegetated stream buffers, drainage ditches or in low areas of fields. Roots of these species can enter and proliferate inside perforated tile drains where the tile carries a source of water during the growing season, especially where soil moisture may be less available in the nearby surrounding soil. Roots may proliferate faster when tile water also carries plant nutrients that may leach from farm fields.

Dry-site plant species rarely cause tile plugging problems although have been known to occasionally plug tile if the perforated tile carries the only source of moisture. Orchard trees for example, prefer moist but well-drained soil and rarely plug underlying tile drains. Forest trees such as white or red pine, red oak and sugar maple prefer drier soil and would rarely plug nearby tile.

Backfill soil that is used to bury tile during installation of the drainage system is generally more loosened than surrounding undisturbed soil which allows roots to grow more freely down to the tile. Root clods within tile have been known to break free and move downstream, sometimes to plug the tile elsewhere. It can be difficult to find the source of problem vegetation where roots have broken free and traveled down the pipe.

Where tile is to pass underneath a permanently vegetated stream buffer to an outlet, drainage contractors can install non-perforated continuous pipe, or header tile, under the full width of the vegetated buffer right to the outlet. Since non-perforated pipe has no holes, plant roots from the overlying vegetative buffer, such as horsetail weeds, cannot enter and proliferate to plug the pipe. The final 8 to10 feet of pipe to the outlet is often a section of galvanized non-perforated steel pipe.

Tile plugging by plant roots is not a new issue. It is an old issue that has been learned by many years of field experience. For best management practices along stream buffers, guidelines on this tile plugging discussion can be found in OMAFRA Publication 29, Drainage Guide for Ontario, drain management problems.

Fibrous roots of overlying stream buffer vegetation can aggressively
plug perforated tile drains

This narrow grassed buffer is being widened and improved by adding a few trees each year. To keep roots out of tile drains, use non-perforated continuous pipe under buffers