Chapter 21 Starting From Scratch: Growing On Seedlings and Saplings

Most of us field collect material or buy training stock from bonsai nurseries or garden centers that is relatively close to the working size of the final tree. Yet if you have space, do a little advance planning, and are willing to wait a couple years, buying and growing out your own nursery stock can be a fun and much less expensive alternative.

I first became curious about how bulk nursery stock is produced when I was grafting apple trees. I learned that most rootstock used in the US is grown by bulk producers in Washington and Oregon. I subsequently learned there are other bulk suppliers who grow huge numbers of a few types of trees and shrubs (say, only boxwoods, or only azaleas.) Sizes of starter trees called liners range from six inches long and a third of the diameter of a pencil to two feet long and as much as 3/4-inch caliper. Liners usually are 1 to 4 years old when they are sold.

A newly emerged pine seedling. Seedlings this size are sold in production flats of 24-72 “Year 0 seedlings” that are overwintered in their sprouting tray, then transferred in spring to individual root training pots to continue development. Link to image source.

A production liner nursery near London. Seedlings have been transplanted into cone-pots and are at various stages of growth. Newly transplanted seedlings are in the lower right and center, while older seedlings with more foliage are in the pots to the left side and rear. Trees are watered and fertilized simultaneously (ferti-gation) by the tower sprinklers. These trees are being trained in cone-pots to maximize tap root development, so likely are being grown for use in reforestation. Link to image source.

By optimizing the growing conditions, liner nurseries produce tree seedlings with much greater growth each year.

1. 2. 3.

Images 1 and 2 show 3-4 year old “wild” tree seedlings growing in open ground. Comparably sized commercial liners typically would be 1-2 years old. For comparison, Image 3 is a 2-0 (i.e., 2 year old) commercially grown Ponderosa pine liner. Link to image 1 source;image 2 source;image 3 source, original by Thomas D. ‘Tom’ Landis, USDA Forest Service, Bugwood.org.

Liners can be planted in open ground or potted up in containers to produce finished nursery stock for sale. Properly managed, liners for some fast-growing species like maples can reach 6 feet or taller in 5 years. Not all species will grow that large so quickly, but even slow-growing species can be pushed to grow faster than they would if simply left to grow on their own.

Fir liners that have been planted out in open ground to begin developing their roots and branches. The two on the left are probably 2-0 liners, while the one on the right is a 3-1 or 4-0 age class. After 1 year in the ground, the two smaller liners can be root pruned in fall then lifted and transplanted in spring to a location with more growing space. Link to image source.

One of the advantages of liners for growing pre-bonsai stock is that their root development can be actively managed to meet our specific needs. Intensive root management is already common practice for most commercially species. For example a strong taproot is beneficial for full size trees, so these trees often are grown out in tall, narrow tree pots. Conversely, liners being grown up for pre-bonsai need to be grown in wide shallow containers that encourage lateral roots instead.

A 3-0 or 4-0 pecan liner in a narrow cone-pot. These containers are designed specifically to encourage formation of long straight taproots and main leaders. Link to image source.

Field-grown 1-4 year old bare-root liners are available for $2-8 each, and are available in bulk for lower prices. So if you are adventurous and willing to wait you can get up to a dozen trees for the same cost as one larger tree or shrub. You can train several, and if they do not work out in the end, they still provided you with more experience growing and styling for just the cost of time and soil.

21.1 When To Order Trees?

November through February are the months to place orders for bare-root liners and saplings for delivery in spring. It is a good idea to place orders early; all available stocks of popular cultivars can sell out by the end of December. Bare-root liners are lifted and shipped at the proper time of year for the recipient’s region of the country; for us orders usually arrive mid-March to early April. Some stock can be purchased in small pots so can be shipped safely until mid-May. After mid-May the spring shipping season is over. Potted stock may be available again in September, but bare-root liners will not be available again until the following spring.

When buying seedlings and liners, the rule of thumb is to never try to grow out trees at the edge of their hardiness range. For examples, bald cypress are hardy for USDA Zones 4 to 11. Yet the best areas for growing out seedlings are Zones 5-10. Larger established cypress trees will do fine, but younger liners will expend too much energy just surviving to grow well.

21.2 Getting Started

I reviewed how professional growers build stock and found that with a few modifications of their basic instructions, we can produce high-quality pre-bonsai trees easily. Georgia’s Cooperative Extension (GCE) has published a very good guide to growing deciduous shade trees with trunk calipers of 2 inches or more for the nursery trade. I have combined several excerpts with my comments and observations. The full guide is available here..

Most production trees do not spend much uninterrupted time in the ground. They are lifted, root pruned, and replanted every year or two. This helps ensure nursery trees have compact, branching fibrous root systems, just like we want for bonsai.

The majority of seedling trees are grown in Oregon or Tennessee. Young trees in their first year of growth (either from seed or cutting in the field, a seed bed, or a container) are referred to as 1-0 seedlings or liners; the “-0” indicates they have never been transplanted. A 2-1 designation means the seedlings were grown for one year in the planting bed and then transplanted/root pruned in the nursery, and grown for another 2 years prior to harvesting.

The next stage is referred to as creating a whip. A 1 to 3 year old liner is root pruned and planted in spring and is grown out for one season. The first year’s growth is cut back nearly to the ground during the winter after the first growing season, and a new strong leader chosen from the spring shoots that emerge. The tree at this point is referred to as a one-year whip, indicating to the buyer that the tree they are purchasing has one year of growth after being cut back. The name refers to the tree’s shape; it has a single straight leader with minimal branching.

The goal in most nurseries is to produce whips that will develop into long, straight main trunks. Our first bonsai-specific modification of standard nursery practice is to cut the liner back only part way, and leave 6-12 inches of the original trunk. This begins building trunk taper.

21.2.1 Liner or Whip?

There is a lot of overlap in the sizes of liners and whips. Liners tend to be smaller and shorter; most are less than 18 inches long, and have only the main tap and a few side branch roots. A 1-year whip will be anywhere from 1 to 2 feet long, while a 2-year whip can be 3 to 5 feet long. Whips usually have larger, well-branched root masses.

21.3 Growing Out

Next whips are transplanted in spring into loose, fertile loam and grown out for 1-5 years. Prior to planting, our heavy clay soil needs to be amended with 4 inches of bark soil conditioner tilled into the soil to a depth of 8 inches. This method creates a natural layer of clay hardpan that keeps tree roots shallow. If you choose to use a raised bed, limit the depth to 6 inches. Line the bottom with landscape fabric, then fill it with a mix of two parts bagged black topsoil and one part soil conditioner.

From here on nursery and bonsai stock are treated very differently, so I am going to change experts. The rest of this story is excerpted from another excellent article that describes the process of developing field stock for bonsai. The full article is available here..

During the growing season, each tree lays down new wood to feed and supply its new shoots and leaves. The more new shoots and foliage the tree produces, the more new wood is developed to support this new growth. New wood grows around the outer ring of the trunk and branches, gradually increasing the trunk’s diameter. Therefore, the greater the amount of new growth a tree achieves in a season, the faster the trunk diameter grows.

A tree that is allowed unrestricted growth in open ground will always thicken faster than a tree that is pruned. Similarly a tree in open ground grows faster than a tree in a large container.

Typically, trees will spend the first year establishing roots in the ground with some reasonable top growth. The second year will start to show strong growth and bulking up of the trunk. By the third year you should expect to see extremely vigorous growth; species like maple, elm, or hornbeam can reach heights of 12 ft if left unpruned. Trunk diameter may go from 1/2” as saplings to 2” to 3” at the end of their third year.

21.4 Root Pruning Field Grown Trees

Root pruning your field grown trees will slow down their growth rate some, but also improve root structure. Trees should be root pruned at the start of their third and fifth springs in the ground. This helps keep the root mass close to the trunk.

Pruning should be done in late winter or early spring just before buds break. Take a flat bladed garden shovel and push it into the soil perpendicularly just outside of the drip line of the foliage. Next move out 2-3 inches from the first line of cuts and turn the shovel 45 degrees to the soil. Cut inward and downward under the tree so it can be lifted free. Turn the tree 1/4 to 1/2 turn, and place it back into the original hole. Water thoroughly to settle the soil back into the spaces made by the cuts.

If the soil falls away as the tree is lifted, take the opportunity to inspect the root mass. Prune off any roots close to the trunk that are unsuitable for future use: crossing roots, roots growing at poor angles from the trunk, a thick over-dominant root or very straight roots with little branching or taper. Remove or at least shorten any downward growing roots. Try to remove as little root as possible and no more than a couple of major roots in one year.

21.5 Developing Nebari, and General Care

When you first plant liners pay attention to how you space the roots. This is your best opportunity to ensure that your future fat trunk has an equally impressive nebari. If the tree you are planting has downward growing roots or poor surface roots, consider ground layering it by tying a wire around the base of the trunk. If there is already a good root pattern and strong lateral roots, prune the root ball so it is reasonably shallow then plant the tree on top of a tile, brick or flat piece of wood. As the tree grows, new roots will be unable to grow downwards and the resulting lateral root growth will ensure the tree is easier to collect and has well-spread roots.

For their first season after planting out or after root pruning, care must be taken that the ground is not allowed to dry out more than a couple of inches below the soil surface as the root system will not have had a chance to extend in search of moisture. However, do not keep the soil continually wet as this will actively discourage the roots to grow in search of moisture, making the tree less drought resistant.

Trees over 3 or 4 ft that have a shallow root system should be staked to guard against being upturned by the wind. Tie the tree to a stake using tree-ties to reduce damage to the bark on the trunk. Try to tie the tree low down on the trunk; though it is necessary to steady the base of the tree to stop the roots being disturbed by the wind, repeated flexing of the upper part of the tree in the wind will help thicken the trunk.

Keep weeds that grow around the trees to a minimum especially around young trees that may not be established enough to compete for light or water. Be wary of weeds that might shade out and cause the eventual die-back of lower branches.

Regularly feeding field growing trees is unnecessary, but they do benefit from two applications of a slow-release fertiliser in spring and summer.

21.6 Shoot Pruning Field Grown Trees

The initial goal of field growing should be to develop a thick trunk base and nebari. Until the trunk has developed, there is no need to consider the final branch positions (unless the tree is coniferous). Avoid continually interfering with your tree! Pruning will result in less growth and less increase in trunk diameter. Bear in mind that the more growth the tree carries, the thicker the trunk will become and the more growth it will put out during the forthcoming season. The only pruning that should be necessary is during winter in order to control or redirect the trunk line depending on how you envisage the finished trunk to look.

21.7 Sources

If you are interested in trying your hand at growing your own, check out Musser Forests. Bulk tree seeds are available from Schumacher Seeds.

To find other bulk seedling suppliers search online for the name of the species in which you are interested, plus the terms “liner” or “seedling.” Not all vendors sell to the public; make sure to check before placing an order. Be aware too that most only sell a few species; you will have to spend time hunting if you want to find a source for a particular species or cultivar.