Some retrotransposons spread their heterochromatic marks into neighbouring genes to regulate their expression, but how widespread is this phenomenon? Eichten et al. found that spreading of cytosine methylation and histone H3 dimethylated at lysine 9 (H3K9me2) was associated with only a minority of retrotransposon classes when studied genome-wide in maize. Among retrotransposon-proximal genes, those affected by heterochromatic spreading were expressed at lower levels, indicating that such spreading may have gene-regulatory roles across the genome.