This study examines the ecology and economics of controlling non-crop vegetation in an interior spruce (Picea glauca X P. engelmannii) plantation. Results suggest that retaining some deciduous vegetation may improve forest health, increase fiber yield, and generate larger financial returns. Specifically, the research is set in British Columbia where forest managers have a legal and financial obligation to regenerate the forest following timber harvest. Traditionally, the focus has been on the establishment and growth of conifers. To achieve this goal, most, if not all, deciduous vegetation is removed. However, elimination of broadleaf vegetation can aggravate insect attack on the desired crop species. In 2001, we examined the stocking and health of a 13-year-old interior spruce plantation that had been aerially treated in 1996 with glyphosate. After five years, the herbicide treatment significantly reduced paper birch (Betula papyrifera) competition to a mean of 180 stems per hectare (±144 SEM). At this time, birch competition in the untreated stand averaged 2055 sph (±182 SEM), with a total stocking (deciduous and spruce) of 3465 sph (±238 SEM). Total stems per hectare in the treated stand were 1527 sph (±121 SEM). Spruce in the untreated area had greater height growth and lower incidence of white pine weevil (Pissodes strobi) attack: attack rates in 2001 averaged 9% and 27% in the untreated and treated stands, respectively. Mean 2001 spruce height in the untreated stand was 4.57 m while it was 3.72 m in the treated. However, current height increment did not differ significantly between the untreated and treated stands: 0.60m vs 0.63m, respectively. Differences in tree height are most likely the product of lower insect attack rates and not an inherent difference in site productivity of the untreated and treated stands as successful weevil attacks results in growth loss. Mean diameter at breast height (dbh) increment did not differ significantly (1.02 cm vs 0.93 cm, respectively) between the untreated and treated stands, suggesting that birch stocking at this level does not impede conifer diameter growth and may in fact be enhancing it. The long-term impact of vegetation control was projected for two rotation lengths - economic and biological - using the TWIGS simulation model. The untreated area yielded considerably (35%) more spruce volume per ha and had a 90% larger land expectation value (LEV) at the economic rotation age of 40 years than the treated stand. Projected spruce yield at biological rotation (Age 70) was much 26% greater and LEV was over four times larger. Together, these results suggest that there are both ecological and economic reasons for retaining some birch stocking in interior spruce plantations.