Prune roots of trees/shrubs before planting: freshwater wetlands

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

  • Two studies evaluated the effects – on trees/shrubs typical of freshwater wetlands – of pruning their roots before planting. Both studies were in the USA. One study was in a laboratory.








  • Survival (2 studies): One replicated, controlled study in created wetlands in the USA reported that root-pruned red maple Acer rubrum seedlings had a higher survival rate than unpruned seedlings, 1–2 years after planting. One replicated, randomized, controlled study in a laboratory in the USA found that root-pruned and unpruned Nuttall oak Quercus nuttallii seedlings had similar survival rates, 108 days after planting.
  • Growth (1 study): One replicated, randomized, controlled study in a laboratory in the USA found that root-pruned and unpruned Nuttall oak Quercus nuttallii seedlings grew in height by a similar amount over the first 108 days after planting.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A replicated, controlled study in 1988–1990 in up to five created freshwater wetlands in eastern Massachusetts, USA (Jarman et al. 1991) reported that pruning the roots of red maple Acer rubrum saplings before planting increased their survival rate. Statistical significance was not assessed. After approximately 1–2 years, saplings with roots pruned “several months” before planting had a >75% survival rate, compared to <25% for unpruned saplings. Methods: In the late 1980s, red maple saplings saved from destroyed wetlands were planted in up to five newly created wetlands (excavated from uplands, connected to natural wetlands, planted with herbs and shrubs as well as red maple). The roots of some saplings were pruned before planting. The study does not report the number of saplings planted, the precise number of wetlands planted with red maple, or precise dates of planting and monitoring.

    Study and other actions tested
  2. A replicated, randomized, controlled study in a laboratory in Tennessee, USA (Farmer & Pezeshki 2004) found that pruning the roots of Nuttall oak Quercus nuttallii seedlings before planting had no significant effect on their survival or growth after 108 days. Pruned and unpruned seedlings had statistically similar survival rates 108 days after planting (data not reported). Pruned seedlings also grew in height by a statistically similar amount (lightly pruned: 8 cm; heavily pruned: 10 cm) to unpruned seedlings (13 cm). However, over a shorter period (72 days after planting) lightly pruned seedlings grew less (5 cm taller) than unpruned seedlings (10 cm taller). Heavily pruned seedlings grew 7 cm taller over this period. Methods: On an unspecified date, 144 nursery-reared Nuttall oak seedlings (approximately 25 cm tall) were planted in pots in a laboratory. Immediately before planting, 48 seedlings received each pruning treatment: light (25% of root removed), heavy (75% of root removed) or none. After planting, half of the seedlings were intermittently flooded (10 days flooded/10 days freely drained) whilst half were always “well watered”. Seedlings were monitored for up to 108 days after planting.

    Study and other actions tested
Please cite as:

Taylor N.G., Grillas P., Smith R.K. & Sutherland W.J. (2021) Marsh and Swamp Conservation: Global Evidence for the Effects of Interventions to Conserve Marsh and Swamp Vegetation. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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Marsh and Swamp Conservation

This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation
Marsh and Swamp Conservation

Marsh and Swamp Conservation - Published 2021

Marsh and Swamp Synopsis

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