This study examined whether variation in reproductive allocation with
size could be explained by differences in the trade-off between reprod
uction and growth. Seeds from 32 half-sibling families were collected
from sites differing in mowing frequency and availability of light, nu
trients, and water. Six seedlings from each family were grown in contr
olled environments and photoperiod manipulations were used to control
reproduction. Mass of vegetative and reproductive plants of the same f
amily were compared to assess the trade-off between reproduction and g
rowth. Families collected from habitats with a tall canopy were larger
and experienced a greater decrease in growth with reproduction than f
amilies from habitats where mowing maintained a short canopy. Reproduc
tive output showed no relationship with size, while reproductive alloc
ation (capsule mass to vegetative mass) decreased with size. This decr
ease may be a direct consequence of the increase in reproductive cost
with size. The increase in cost can be partially explained by increase
d allocation to reproductive support structures; large individuals pro
duce capsules on more elongate scapes and have a lower capsule to scap
e ratio. Differences in size and morphology among habitats are presuma
bly the result of selection to avoid damage in mown sites and to avoid
shade and ensure pollination in sites with a tall canopy and reduced
wind movement.