Plant smaller fruit trees. Dwarf and semi-dwarf options are better for planting near septic lines. Standard-size fruit trees can grow roots large enough to affect the functioning of your septic system.
Figure out the best spot to plant the fruit trees. Try to plant them between the septic lines, if you can. There's usually about 3 to 6 feet of space between lines where you can plant the trees. This minimizes the risk of root damage.
Dig out as large a space as possible to plant the fruit tree. This encourage the tree's roots to grow in the area you dug out, rather than into the septic lines. Mix organic materials, such as compost or peat moss, with the soil to improve the quality. Dig down at last 18 inches.
Put a small amount of the dirt and organic material you mixed together into the bottom of the hole you dug out. Then, set your fruit tree inside the hole.
Manually spread the roots of the fruit tree in the direction you want them to spread. When planting near septic lines, you want them to grow in the opposite direction of the lines.
Fill in the hole with the remainder of your dirt and organic material mixture. Make a small mound around the base of the tree so the dirt has room to settle. Step around the dirt to gently pat it down.