Grapevine roots were studied in a heavy clay soil to see how different scion types affect root growth. The roots of grafted vines were denser and had more roots compared to self-rooted vines. The scion type influenced root diameter, density, and the ratio of fine to coarse roots. The roots were most concentrated between 21 and 60 cm deep. The scion type plays a big role in how grapevine roots grow and spread in tough soil, even though we're not sure exactly how.