Use herbicides after tree planting

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

Study locations

Key messages

  • Two of three studies (including two replicated, randomized, controlled studies) in Sweden and the USA found that using herbicide increased the size of planted trees. One study found no effect on tree size.
  • One replicated, randomized, controlled study in Sweden found no effect of using herbicide on frost damage caused to planted Norway spruce seedlings.


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, randomized, controlled study in 1992-1995 in boreal forest in Sweden (1) found that applying herbicide increased the biomass of English oak Quercus robur seedlings. Dry weight (g/seedling) of stems (herbicide: 1.25-1.75; untreated: 0.45-0.50) and leaves (herbicide: 0.95-1.20; untreated: 0.25-0.35) were lower in untreated than herbicide plots. Data were collected in 1995 in herbicide and untreated (control) plots (25 m2) established in summer 1992 in each of six clearcut and six shelterwood (12.5 m2/ha basal area retained) blocks (cut in 1990). All plots were planted with oak seedlings in November 1992.

    Study and other actions tested
  2. A replicated, randomized, controlled study in 1988-1995 in boreal forest in Sweden (2) found no effect of herbicide treatment on frost damage to planted Norway spruce Picea abies seedlings. The percentage of seedlings with frost injuries was similar between treatments (site 1: 6-13%; site 2: 30-43%). Five blocks of four herbicide (glyphosate emulsion applied directly to the leaves of the ground vegetation whenever necessary through 1989-1993) and four control plots (4 × 4 m) were established in 1988 in each of two sites. Data were collected in each plot two growing seasons after planting of spruce seedlings.

    Study and other actions tested
  3. A replicated, randomized, controlled study in 1999-2002 in temperate broadleaf forest in Illinois, USA (3) found that herbicide treatments during reforestation planting increased seedlings stem volume. The stem volume index was higher in herbicide treatments before and after seedling emergence (135 and 115 cm3 respectively) than in control plots (50 cm3). Stem volume index was calculated in 2002 for 40 ash seedlings (planted in 1999) in each control, after emergence (glyphosate) and before emergence (sulfometuron methyl) herbicide treatments (18 × 30 m) replicated in four blocks. Treatments were applied in 1999.

    Study and other actions tested
  4. A replicated, controlled study in 1998-2006 in temperate forest in Louisiana, USA (4) found no effect of herbicide treatment on the height and basal area of planted longleaf pine Pinus palustris trees. Total cover of  understory vegetation was lower in herbicide plots (herbicide: 21%; control 68%). In comparison, longleaf pine height (herbicide: 9.0 m; control 9.1 m) and basal area/tree (herbicide: 12,000 cm2; control 11,600 cm2) were similar between treatments. Data were collected in 2006 in three herbicide (application of triclopyr herbicide without intentionally treating herbaceous plants and vine in 1999, 2001, 2003, and 2005) and three control plots (untreated since 1998) of 0.066 ha. Each plots was planted with 196 longleaf pine seedlings in 1993-1994.

    Study and other actions tested
Please cite as:

Agra, H., Schowanek, S., Carmel, Y., Smith, R.K. & Ne’eman, G. (2020) Forest Conservation. Pages 323-366 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.


Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

Forest Conservation

This Action forms part of the Action Synopsis:

Forest Conservation
Forest Conservation

Forest Conservation - Published 2016

Forest synopsis

What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust