Sow seeds at start of growing season

Overall effectiveness category Evidence not assessed
Number of studies: 3
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Effectiveness

not assessed
Certainty

not assessed
Harms

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Calculating overall effectiveness category

Background information and definitions

Grassland seeds are commonly sown in autumn or spring in restoration projects in temperate regions. Sowing in autumn may result in early germination of plants allowing them to become established before other non-grassland species. However, sowing in autumn may also result in more seeds dying as a result of waterlogging in winter and so, in some cases, spring sowing may produce better results.

Study locations

Key messages

Three studies examined the effects of sowing seeds at the start of the growing season on grassland vegetation. Two studies were in the USA and one was in the UK.

VEGETATION COMMUNITY (2 STUDIES)

Overall richness/diversity (1 study): One replicated, randomized, controlled study in the USA found that sowing seeds in spring increased plant diversity compared to sowing in autumn.
Sown/planted richness/diversity (1 study): One replicated, randomized, paired, controlled study in the UK found that sowing seeds in spring increased the number of sown species compared to sowing in autumn.

VEGETATION ABUNDANCE (1 STUDY)

Sown/planted species abundance (1 study): One replicated, randomized, paired, controlled study in the UK found that sowing seeds in spring increased the cover of sown grass and forb species compared to sowing in autumn.

VEGETATION STRUCTURE (0 STUDIES)

OTHER (1 STUDY)

Germination/Emergence (1 study): One replicated, paired, controlled study in the USA found that sowing seeds in spring led to similar emergence of forb seedlings compared to sowing in winter.

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

A replicated, randomized, paired, controlled study in 1994–1996 in two ex-arable sites in Scotland, UK (Lawson et al. 2004) found that sowing seeds in the spring increased the cover of sown forb and grass species, as well as the number of sown species, and reduced the cover and species richness of non-sown species when compared to sowing in the autumn. More species that were sown were present in areas where seeds were sown in spring than areas where seeds were sown in the autumn, and the same pattern was true for cover of sown forb and grass species (no data reported). Similarly, there were fewer non-sown species in areas where seeds were sown in spring compared to areas where seeds were sown in autumn, and their cover was also lower (no data reported). Before seeding, sites were ploughed and harrowed. In May 1994, seeds of 18 species were sown at a rate of 4 g/m² in four 3 x 9 m plots, and seeds were sown in another four plots in October 1994 at each site. Plant cover and species richness were estimated in June/July 1995 and 1996 using a 1 x 1 m quadrat placed in each plot.
Study and other actions tested
Referenced paper
Lawson C.S., Ford M.A. & Mitchley J. (2004) The influence of seed addition and cutting regime on the success of grassland restoration on former arable land. Applied Vegetation Science, 7, 259-266.
A replicated, paired, controlled study in 1998–1999 in tallgrass prairie in Iowa, USA (Williams et al. 2007) found that sowing a local seed mix in spring did not change the number of forb seedlings that emerged when compared to sowing in winter. Plots sown in spring contained 18–32 seedlings/m², while those sown in winter contained 14–24 seedlings/m². Six 15 x 20 m plots were sown with 23 native forb species at a rate of 350 seeds/m² in November 1998 (winter seeding), and six plots were sown in April 1999 (spring). All plots were burned before seeding and mowed weekly from May to September. All plants in seven randomly placed 0.25-m² quadrats/plot were identified every month from June to September.
Study and other actions tested
Referenced paper
Williams D.W., Jackson L.L. & Smith D.D. (2007) Effects of frequent mowing on survival and persistence of forbs seeded into a species-poor grassland. Restoration Ecology, 15, 24-33.
A replicated, randomized, controlled study in 2005–2010 in two grassland sites in Iowa, USA (Martin & Wilsey 2012) found that sowing seeds in spring increased plant diversity compared to sowing seeds in autumn. In areas where seeds were sown in spring, plant species diversity was higher than in areas where seeds were sown in autumn (data reported as Simpson’s diversity index). In 2005, at each site, fifty-eight 5 x 5 m plots were sown with grass and/or prairie seeds in spring and 58 plots were sown with grass and/or prairie seeds in autumn. In 2006–2010, point intercept sampling was using to estimate species diversity in each plot.
Study and other actions tested
Referenced paper
Martin L.M. & Wilsey B.J. (2012) Assembly history alters alpha and beta diversity, exotic–native proportions and functioning of restored prairie plant communities. Journal of Applied Ecology, 49, 1436-1445.

Please cite as:

Martin, P.A., Ockendon, N., Berthinussen, A, Smith, R.K. and Sutherland W.J. (2021) Grassland Conservation: Global evidence for the effects of selected interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Grassland Conservation

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