Stanley plum trees are one variety of European plum trees (Prunus domestica). European plum trees are the favored plum both for eating fresh and for canning. Stanley plum trees are self-fruitful trees that produce fruit that is dark-skinned and very sweet. They can grow about 15 to 20 feet tall and are hardy in USDA hardiness zones 5 to 9. Plant Stanley plum trees in full sun, and try to provide them a soil pH between 4.5 and 6.5.
Fill 5-gallon plastic buckets, or any like containers, with water. Place each of the bare-root Stanley plum trees into the water and let them soak over night. (Soaking the roots of bare root trees helps plump them up in case they've been dried out.)
Dig planting holes for the Stanley plum trees that are twice the width and depth of the entire root system. If planting more than one Stanley plum tree, like in a row, dig each of the holes so they are 20-25 feet apart from each other.
Mix a 5-gallon bucket full of compost into the soil that was removed from the planting hole. Then add 1 cup of all-purpose, balanced, granular fertilizer such as 10-10-10 or similar.
Create a mound of soil in the center of each hole that is approximately half the height of the planting hole.
Remove the bare root Stanley plum trees from the containers they have been soaking in and spread out the roots of the bare root Stanley plum tree over the mound of soil. Look for where the bud union or graft union is, typically approximately 1 inch above the soil line.
Scoop in the soil, compost and fertilizer mixture into the planting hole once you are sure the Stanley plum tree is sitting at the correct height in the hole. Compress the soil in and around the trunk of the Stanley plum tree to eliminate any air pockets. Then, create a 3- to 4-inch-high circular berm of soil that is approximately 24 to 36 inches in diameter around each of the Stanley plum trees. The berm of soil helps when watering to let water accumulate, so it can soak down to the root system.
Water each of the Stanley plum trees thoroughly. Then, spread a 2- to 3-inch-high layer of mulch around the stem of each Stanley plum tree. You can use pine bark, grass clippings, leaves or other similar material. Once you see new growth appearing on the Stanley plum trees, keep them watered with the equivalent of about 1 to 2 inches of water weekly.