Primary succession is limited both by ecosystem development and plant dispersal, but the extent to which dispersal constrains succession over the long term is unknown. We compared primary succession along two co-occurring arctic chronosequences with contrasting spatial scales: sorted circles that span a few m and may have few dispersal constraints; and glacial forelands that span several km and may have greater dispersal constraints. Dispersal constraints slowed primary succession by centuries: plots were dominated by cryptogamic soil after 20 years on circles, but after 270 years on forelands; plots supported deciduous plants after 100 years on circles, but after >400 years on forelands. Our study provides century-scale evidence suggesting that dispersal limitations constrain the rate of primary succession in glacial forelands.