Hilchos Shemittah v’Yoveil 3:10

If unripe fruits from the sixth year enter shemittah, or if unripe fruits from shemittah enter the eighth year, we may not oil or perforate them. When the Temple is standing, we may not build steps into valleys after the rains stop in the sixth year because this is considered preparing for shemittah.

Hilchos Shemittah v’Yoveil 3:11

Even nowadays, we may not plant or graft trees, nor extend vines into the ground in the sixth year unless there’s enough time for it to take root and remain after taking root thirty days before the Rosh Hashana of shemittah. Taking root normally takes two weeks. These particular activities are prohibited even when the Temple isn’t standing because of the possibility that an observer might think that they were planted during shemittah. Therefore, if someone planted, grafted or extended in the sixth year at least 44 days before Rosh Hashana, he may let it remain; if it was less time than this, he must uproot it. However, if he doesn’t uproot it, its fruits are permitted. If the owner dies before uprooting it, his heir must do so.