Step by Step guide to successful repotting
This checklist is not meant to be a How To treatise, but rather a reminder of the steps needed for a successful bonsai repot. Each tree is different and may require many differing techniques to prune, clean, and anchor the tree into the pot, which we cannot cover here.
1 Determine the reason for repotting;
Change of pot, change of planting angle, or position.
Health, which can include loss of percolation - water does not adequately permeate the soil, staying too dry, or soggy, organic soil that stays too wet. These factors will help guide you in the process of repotting.
2 Determine the health of the tree. Is it growing vigorously? Are there signs of stress in the leaves or needles? Are the new buds healthy? Do I have adequate foliage mass to drive recovery of the roots? How much can the roots be pruned?
3 Go light on watering before repotting, but never let the soil get dry.
4 Gather supplies and tools. Select a soil mix and have it ready. Have a drainage layer and screened moss top dressing at hand.
5 Work on a level surface in an area that can get dirty, very dirty. Be able to clear the surface after each step so that you can accurately see what you are doing.
6 Cut the tie-in and drainage hole wires and make sure that they easily clear the drainage holes by bending any tabs to the interior of the hole.
7 Use a root sickle with a scraping motion to remove the outer edge of soil at least 3/4 of the way around the pot. Clear out about 1/2 inch around the perimeter between the pot and root ball. Make sure to go all the way to the bottom of the pot so that there are no obstructions to removing the rootball. Old roots can grab tightly.
8 Remove the tree by pushing up diagonally on a non-delicate area. Use a jin or the bottom base of a branch. Never touch the trunk if possible, especially on a conifer with flaky bark. Some deciduous trees stain easily from the soil on your hands.
9 If the tree is not an established bonsai, such as nursery stock or collected material, begin by clearing soil and small roots to find a stable nebari. Identify your biggest obstacle to getting the tree into a bonsai pot, whether it be to reduce the length of large roots on collected trees or the depth of a nursery container. This will be your first priority if you do not have an established root ball.
10 After establishing the level of the nebari, place the tree on it’s side with the weight of the tree resting on the strongest part of the root ball. The bottom of the root ball should be perpendicular to the work surface with the foliage mass hanging free and clear beyond the edge. Provide adequate support for the tree (a helper is great for larger trees) so that it is stable while you work.
11 Trim the root ball flat. If you are right handed, work with the trunk on the left and root ball in front of you. This gives your scissors a better angle at the root ball. Use a rake to comb out the roots and trim with sharp root scissors. Clean up all stubs with scissors and root cutters. Make sure to clean up underneath the base of the trunk on deciduous trees. You may need to flip the tree 180 degrees
to work the opposite side of the rootball. The bottom should now be flat and the tree resting at the desired planting angle, and the thickness desired to fit into the pot. The goal is to force the roots to grow sideways, thus developing the nebari and thickening the trunk.
12 Now place the tree back into the normal position and start combing out the roots on top of the root ball in a radial direction. Correct crossing roots by trimming or moving and trim anything that sticks up. The angle of the roots should slope down gently and away from the trunk. Only remove that which is necessary and never bare root a conifer.
13 Trim the sides to at least 1/2 inch from the edge of the pot. Cut the coarser roots even closer to the trunk. End by cleaning out the old soil 1/4 inch farther into the root pad than the trim line to allow the new soil to integrate into the roots and existing soil mass.
14 Test the tree in the selected pot for size, placement, and clearance, and of course aesthetics.
15 When you are satisfied, prepare the pot by adding drainage hole covers and tie down wires as needed. Clean it inside and out with a soft brush - no abrasives.
16 Add a drainage layer of coarser soil into the pot. Add a thin layer of regular soil over this, just filling the pores for the aeration layer. Make a mound of soil in the middle, high enough so that the tree can be settled back down into the pot.
17 Lock the turntable. Place the tree in the pot. Working from the front, settle the tree by placing hands on both sides of the root pad and firmly rotating slightly left and right until reaching the final position. Double check the level of the roots, position side to side and front to back, and the inclination of the trunk from front and the side. The tree should be centered from front to back to allow the roots and trunk to grow evenly. The baseline should be level with the top of the pot.
18 Once the tree is set, proceed to tighten the tie wires if it has a well established root pad. If the tree is loose and less developed, work more soil around the roots until a firm base is established. Then proceed to finish the tie in. If the tree leans to one side, tighten the side away from the lean last to provide more support.
19 Fill in the rest of the pot with soil, mounding it generously. Use chopsticks to work the soil between roots. If there are no roots in area, using chopsticks will do no good. Be sure to probe for voids and fill those first. Be firm but do not pack the soil too tight.
20 Use a brush to remove excess soil and taper the level. Hold the brush flat against the soil. The soil level should slope to the edge of the pot stopping about 1/4 below the rim to allow water to catch.
21 Use a trowel to tamp down the soil. This will help keep it from washing away while watering.
22 Place sifted mixture of half New Zealand sphagnum moss (Orchid moss) and fresh green moss on the surface for moisture retention and soil stability.
23 Water thoroughly until the water runs out clear from the bottom. We want to wash away any dust remaining in the soil.
24 Place in regular sun if the tree is healthy. Protect the tree from freezing and frosts. A fertilizing schedule may begin about one month later
03.04.19 ©2019 Scott Elser