You have to transplant grass trees carefully if they are to survive. Grass trees grow very slowly: even under the best conditions, a grass tree will take 50 to 100 years to grow 3 feet. The problem is exacerbated by the fact that half of a grass trees' roots are pruned when it is dug up for sale. If purchased from a reputable dealer and planted in a well-drained, sunny, site, the transplanting should succeed.
Dig a hole that is twice the circumference of your grass tree's root ball or the container that it is currently growing in.
Fill a large bucket with half of the excavated soil. Add an equal amount of garden soil and 5 tablespoons of slow-release fertilizer (or the amount specified by its manufacturer) and mix well.
Plant the soil so that the grass tree's root crown (the point where its roots meet its trunk) is 1 inch higher than the surrounding earth. Do not cover the plant's roots with more than 1 inch of soil. Fill in half of the soil, water it and then finish filling the hole. Pat the soil down with your hands to firm it when you're done.
Water the planting area with a slow-running hose until the soil is moist but not soaking. Keep the soil moist to the depth of its root ball by watering it whenever the top few inches of the soil dry out. Check the soil frequently--insert a wooden dowel into the soil to check its moisture level. You may have to water roughly once weekly.