Red Stalk Celery Apium graveolens Rare – Heirloom An 18th century English heirloom with rich celery flavor. Stays red when cooked. Widely branching plants are harder than green types. Planting Depth: 1/4″ Soil Temp. for Germ.: 60-70 F Days to Germ.: 21 Plant Spacing: 6-12″ Days to Maturity: 120 Full Sun/Partial Shade. Water Often