Chemical defense
Growth is typically negatively correlated with chemical defense allocation because of the cost of secondary metabolite production (Herms & Mattson 1992). Plants produce a wide variety of defense chemicals that can inhibit pathogens (Bednarek & Osbourn 2009). For example, the invader Solidago canadensis can suppress soil pathogens via allelochemicals including flavones, phenolics, and saponins (Zhang et al.2009, 2010). While some species are known to produce relatively high concentrations of these compounds, comparisons between invaders with high and low production of these compounds is required to understand cost-benefit relative to other defense traits.