Kilayim 1:8

Examples of grafting a tree and a vegetable (which the Sages prohibit) include planting vegetables in a sycamore stump and grafting ruta (herb-of-grace) onto cinnamon. One may not plant a shoot from a fig tree into an onion plant in order to lower the latter’s temperature, nor may one put the shoot of a vine into a melon in order to hydrate the former. One may not put the seeds of a gourd into mallow (a family of flowering plants including okra and cacao) because this constitutes grafting two types of vegetable.

Kilayim 1:9

If someone buried turnips or horseradish under a vine, he need not be worried about kilayim, Sabbatical produce, or tithes. Additionally, as long as some of the buried plant’s leaves are exposed, it may be removed from the ground on Shabbos without fear of violating the prohibition against harvesting.