Question: When and how should I fertilize rhubarb?
Answer: Rhubarb is a heavy feeder. Mix compost, rotted manure, or anything high in organic matter into the soil when planting. But don’t add a chemical fertilizer when planting rhubarb or during the first year of growth, as direct contact with nitrates can kill the roots. In future springs, apply a light sprinkling of a high-nitrogen fertilizer (25-3-3 or 10-6-4) when the ground is thawing or has just thawed, so that the fertilizer will go into the ground and not harm the roots.