How to Sow Cucumbers Sow cucumbers into small pots of seed starting or general-purpose potting mix. Sow two seeds about an inch (3cm) deep, then water well. Cucumbers need temperatures of at least 68ºF (20ºC) to germinate, so either place pots in a propagator for speedier germination, or simply wait until late spring to get started. Once the seedlings appear, remove the weakest to leave one per pot.