Thin beet seedlings when they are three inches tall by removing the entire portion of the seedling that is above the ground. Even if you don’t like eating beet greens, you still need to prune your beet plants in order to keep the leafy older plants from pushing their way into their neighbors space and to thin out the younger plants.
When seedlings reach three inches in height, trim them down to ground level using garden scissors and leaving three inches of space between each plant. For older stems, twist the outer leafy stems one inch from the plant’s base and gently tug the stems away while continuing to twist. Even after your beet plant has been harvested, improperly removing the tops will result in less flavorful roots. To keep juices from running, never chop the tops off at the very base, instead carefully twist the tops away at least one inch above the roots.
Keep pruning beet tops during the growing season, focusing on outer leaves and every now and then, the overly-tall central leaf. Never remove more than one-third of each plant’s foliage at a time because beets need some of their leaves to continue growing and producing healthy roots and tops. Depending on the variety you planted, remove the entire plant after 50 to 70 days. Beet roots left in the soil for too long start to become woody and the greens become bitter.
To extend the harvest of both roots and greens, plant beets every three weeks. In mediterranean climates, beets go into the ground from March through May and again starting in late August.