Rhubarb is a cold-hardy perennial, often treated as a fruit in the kitchen despite being botanically a vegetable. A healthy plant can remain productive for 10 to 15 years, meaning its initial planting location is a long-term commitment. Choosing a permanent spot that meets its specific environmental and soil needs is paramount for a sustained, abundant harvest, as the plant cannot simply be moved after it is established.
Optimal Sunlight and Climate Factors
The ideal planting location for rhubarb depends on the local climate and sunlight. In northern climates, where summer temperatures are cool, full sun exposure (at least six hours daily) is preferred to maximize growth.
In warmer regions, the plant’s needs shift, and light afternoon shade becomes beneficial. Shade during the hottest part of the day prevents stress, which can lead to premature seed stalk formation, known as bolting. Rhubarb thrives best when the average summer temperature stays below 75°F, making excessive heat a limiting factor.
The plant requires a defined period of cold winter dormancy for strong spring growth. Optimal production requires the crown to have an extended chilling period, typically six to eight weeks below 40°F. This explains why rhubarb cannot be grown successfully in tropical or subtropical areas that lack a hard winter freeze.
Essential Soil Preparation and Drainage
The longevity of rhubarb necessitates deep and thorough preparation of the planting medium. The plant requires deep, rich, and well-draining soil, ideally a sandy loam. Poor drainage is the greatest threat, as soggy conditions quickly lead to crown rot and destroy the perennial root system.
The soil’s pH should be slightly acidic to neutral, optimally between 6.0 and 6.8. Since the roots will be undisturbed for years, the entire planting area should be loosened to a depth of at least 12 inches. This deep preparation improves root development and ensures long-term health.
Pre-planting soil enrichment requires incorporating significant amounts of organic matter, such as well-rotted compost or aged manure. This material should be mixed into the entire planting area, not just the individual hole, to improve texture and fertility. Organic matter enhances both water-holding capacity in lighter soils and drainage in heavier clay soils.
Long-Term Placement and Spacing Needs
Given the perennial nature and large mature size of rhubarb, placement requires careful consideration. A mature plant can spread three to four feet in diameter, needing ample room to grow without overcrowding. Crowding results in smaller, less productive stalks and reduces airflow, increasing the risk of disease.
Planting should occur away from the main annual vegetable garden where the soil is frequently tilled. This separation prevents accidental damage to the crown, ensuring it remains undisturbed for its lifespan. Also, avoid planting near large trees or established shrubs whose extensive root systems will compete for water and nutrients.
If the planting site has heavy soil or questionable drainage, creating a slight mound or raised bed is a practical solution. Planting the crown slightly higher than the surrounding soil line encourages water to drain away from the central growing point.