Role of Grevillea. The density of Grevillea planted in agroforests had a negative effect on berry dry weight, a measure of coffee quality. We cannot easily explain this result, nor can we even ascribe it directly to Grevillea density, which negatively covaries with native tree cover. Nevertheless, Grevillea cover is more open and is unlikely to be as effective in providing a favorable understory microclimate that buffers coffee from weather fluctuations. Grevillea also drops its leaves frequently and the resulting litter often smothers the coffee plants. Farmers state that both these factors adversely affect berry development, although we have no empirical evidence to support this. We also recognize that Grevillea trees provide many benefits to farmers as timber revenue and as a stand for pepper (9, 26); the potential negative effects of Grevillea need to be set against its benefits.