Garden days: December 2026

Best days of the month

• Above-ground crops (greens, tomatoes, cucumbers): 15, 16, 17, 20, 21
• Root crops (carrots, beets, potatoes) and pruning: 5, 6, 7, 25

In December the limit is daylight, not the Moon

Growth is driven by the total light a plant receives, and in the depth of winter that total falls below what a leaf crop needs to gain weight, which is why a greenhouse in December preserves plants rather than growing them. Market gardeners in cold climates plan around this directly and call the stretch a standstill: seed sown then germinates and waits for the day length to come back. No arrangement of phase and sign changes it, and a calendar suggesting otherwise promises something the sky does not supply. What December's dates are genuinely good for is the indoor version - sprouts, microgreens and forced onion, all of which run on stored energy rather than on daylight. Four belowground dates and six barren ones complete the month, and two more are left blank entirely, because the tradition rests on the day of a lunation.

Days of December 2026

This is folklore, not agronomy: the Moon’s position on this page is computed with Swiss Ephemeris, no research links the phase to a harvest, and seeds sown on an “unfavourable” day still grow. How the rules work.