Wait until after all threats of frost have passed in the spring and the plants have at least two sets of leaves on them before you transplant your castor bean plants.
Look for an outdoor planting location that receives at least three hours of sunlight per day. The soil should be loamy, well-drained and not soggy.
Loosen the top 3 inches of soil in the desired planting location using a wide-toothed rake.
Spread a layer of pure nitrogen fertilizer over the top of the planting area using the rate specified on the packaging for your sized area. Mix the fertilizer into the soil well with the wide-toothed rake.
Dig a hole that is large enough to accommodate the roots of the castor bean plant, using a shovel. Remove all of the soil form the initial planting pot without breaking it up, since castor bean plants do not like having their roots disturbed. Place the roots into the hole and fill in the hole with soil.
Water the soil under the newly planted castor bean plant well until it is completely damp.