How to Space and Thin Celeriac Plants for Large, Uniform Roots

Celeriac is a slow-growing, cool-season crop, and one of the most common mistakes gardeners make is overcrowding. Over decades of growing root vegetables in Sonoma Valley, I’ve learned that proper spacing and timely thinning are essential for producing large, smooth, flavorful celeriac roots. Crowded plants compete for water, nutrients, and light, resulting in small, misshapen bulbs and uneven growth.

Table of Contents

Proper Spacing for Celeriac

After years of trial and error, I recommend 8–10 inches between plants within a row, with 12–18 inches between rows. This generous spacing allows each plant enough room to expand its swollen stem base fully. In tight soil, you may need slightly more space to prevent roots from bumping into one another.

Wide rows also improve airflow, which reduces the risk of foliar diseases—a factor I’ve noticed is critical in humid or cool-season gardens.

Thinning Seedlings: Timing and Technique

Thinning is just as important as spacing. Once seedlings develop their first true leaves, I assess their vigor and remove the weaker plants. I usually leave the strongest seedling at each station. Early thinning prevents root crowding and allows the remaining plants to reach full size.

Use scissors or gently pull seedlings to avoid disturbing the neighboring roots. Over the years, I’ve learned that early, careful thinning produces smoother, more uniform bulbs than trying to adjust spacing later.

Additional Tips for Even Growth

Keep soil loose and evenly moist: Crowded roots compete more intensely when moisture is inconsistent.
Mulch between plants: This stabilizes soil moisture and encourages uniform root swelling.
Fertilize lightly: Side-dress with compost or balanced organic fertilizer midseason to support the developing roots.

Spacing and thinning may seem minor, but they are the most impactful steps for a bountiful, beautiful celeriac harvest.

Bottom Line

Give celeriac enough room and thin seedlings early for large, uniform roots. Proper spacing sets the foundation for flavorful, smooth bulbs every season.