Tree and shrub roots are drawn toward the moisture and nutrients in a septic drainfield, and can grow into pipe joints, crack lines, and clog the surrounding soil over time. It develops slowly, usually over years, which is why the fix is prevention — keeping deep-rooted plants well back from the field — rather than a quick repair once it has taken hold.
Roots do not need a crack to start a problem; they can find their way into pipe joints and small gaps that already exist by design, then widen them over time as they grow. Once inside a pipe, roots restrict flow and can eventually block it outright, in addition to the physical damage they do to the pipe itself.
Species matters: fast-growing, water-seeking trees (many willows and poplars, for instance) are more aggressive intruders than slower-growing, deeper or more contained root systems. Distance also matters more than species alone, since even a well-behaved tree’s roots will eventually reach a field planted too close.
The reliable prevention is landscaping choice: keep large trees and shrubs at a meaningful distance from the field, and favor grass or shallow-rooted groundcover directly over it. Once intrusion is established, the field usually needs excavation and pipe repair or replacement, plus removing or root-barrier-isolating the offending plant, since simply cutting the visible roots back does not stop regrowth into the pipe.
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The moisture and nutrients in the effluent moving through the field are attractive to roots, more so than typical surrounding soil, which draws growth specifically toward the pipes.
Fast-growing, water-seeking trees are the most aggressive intruders, but any tree or large shrub planted close enough will eventually reach the field.
Often the affected section of pipe can be excavated and repaired or replaced, along with removing or isolating the source plant, without replacing the whole field, but this depends on how much damage has occurred.
Guide last reviewed 2026-08-31.