A common misunderstanding among people who are new to bonsai is that trees with big, thick trunks must have been trained for decades to get that size, and that a seedling with a thin trunk will eventually grow a thick trunk even though it is in a bonsai pot.
Unfortunately, a tree’s trunk and branches will only get thicker slowly if it grows in a small pot with its roots squished together and its top growth regularly cut back.
Large bonsai with thick trunks are almost always grown in the ground before being planted in a pot. Some are purposely grown in the field, while others are collected from mature trees.
During the growing season, when a tree makes new growth, it stores new wood to feed and stock its new shoots and leaves. The tree grows more new wood to support its new growth as it makes more new shoots and leaves. This new wood grows around the outside ring of the trunk and branches in a nearly direct path from the new shoots back through the trunk to the root system, making the trunk wider over time. Thus, the girth of a tree’s trunk grows bigger as the amount of new growth it gets higher in a season.
A tree that is allowed unrestricted growth will always thicken faster than a tree that is pruned.
Planting a tree or shrub in the ground is the best way to make sure it grows freely. Growing it in a large pot is an option, but it’s not the same as growing it in the ground. The main reason for this is that soil in a container doesn’t move as freely as soil in the ground. If you plant trees in containers that are too big, they may not grow as quickly. See Overpotting).
Field-growing methods can be used on any piece of land. If you don’t have access to land, which happens a lot of the time, you can grow trees in your garden and enjoy them as part of regular garden plans, as “temporary” 5–10 year hedges, or as “temporary” garden specimens. With a little work, you can also make raised beds just for field growing. The walls of the raised beds can be made of bricks or wooden planks, and they should be filled with good soil.
You can grow any kind of tree or shrub in the field as long as it can handle the weather where you live. Native species naturally do well in your area’s climate and will therefore respond best. Other species will grow well, but it may take longer for them to get established in the ground before they really start to grow strong.
Field growing is possible with trees of any age or size, as long as they are fully grown enough to compete with grasses and weeds for water and light. If you can’t cover them for the first year, cuttings, seedlings, or saplings should be at least two years old before they are planted outside.
Typically, trees will spend the first year establishing in the ground with some reasonable top growth. The second year will start to show strong growth and bulking up of the trunk. You can expect very strong growth by the third year. Some species, like Trident Maples, Elms, and Hornbeams, will have easily grown to 12 feet by now if they are not pruned.
When it comes to trunk diameter, species that grow quickly like Tridents, Field Maples, Hornbeam, Elm, and Scots Pine can see their trunk diameter go from 1/2 inch as saplings to 2 to 3 inches by the end of their third year in the ground. Peter Chan of Heron’s Bonsai talked about how a Field Maple tree with a 1-inch diameter that he planted 18 years ago had grown to have a 15-inch trunk!
If the tree you want to plant has roots that grow downward or poor surface roots, you might want to ground layer it by wrapping a wire around the trunk’s base. There should already be a good root pattern and strong lateral roots. Cut down the rootball so it is not too deep, and plant the tree on top of a tile, brick, or flat piece of wood. As the tree grows, new roots won’t be able to grow downwards. This means that the tree will have better root spread and nebari, and it will be easier to collect.
Four years ago, this Tilia cordata, or Small Leaved Lime, was put in the ground on top of a tile. Last Spring it was lifted and root pruned for the first time. After a year, the rootball is flat and has strong side root growth, perfect for bonsai, as you can see below.
Linden in 2002 after growing on top of a tile in the ground for 2 years.
The same Linden in 2005 after growing on top of a tile in the ground for 5 years.
The Linden in 2016, when the trunk, branch structure, nebari, and a lot more ramification were fully grown!
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One good thing about field growing is that a lot of trees can be planted out to be used as bonsai in the future and then left alone to grow without a lot of care.
You should improve the soil before planting, but you don’t have to (or shouldn’t) expect it to be as good as the soil used for container growing. To open up clay soils and make them drain better, you can add grit, sand, or compost. To improve water retention and nutrition, you should add compost to thin gritty soils.
It’s important to keep the ground from drying out more than a couple of inches below the surface for the first season after planting or root pruning. This is because the roots won’t have had a chance to spread out in search of water. But don’t keep the soil wet all the time. This will stop the roots from growing in search of water, which will make the tree less resistant to drought.
Trees taller than 3 or 4 feet and with shallow roots should be staked so the wind doesn’t blow them over. Tie the tree to a stake using tree-ties to reduce damage to the bark on the trunk. Try to tie the tree low on the trunk. The base of the tree needs to be kept steady so that the wind doesn’t disturb the roots, but bending the top of the tree over and over in the wind will help the trunk get thicker.
Cut down on the weeds that grow around the trees as much as possible. This is especially important around young trees that may not be fully grown yet and could be competing for water or light. Be wary of weeds that might shade out and cause the eventual dieback of lower branches.
Before planting, weed-killing membranes can be put on the top of the soil. This will stop weeds from growing, but it might be hard to root-prune or collect your trees in the future. Another thing to keep in mind is that low-growing weeds won’t hurt the tree and can make it much faster for the mature bark to show.
Field-growing trees don’t need to be fed often, but they do do better with one application of Growmore (or a similar slow-release fertilizer) in the spring and one in the summer, especially if the soil is thin and full of rocks.
Primarily, the purpose of field growing is to develop a thick trunk base and nebari. If the tree isn’t a conifer, you don’t need to think about where the branches will end up until the trunk has grown. Once the trunk reaches its full height and width, all of its branches will be too thick to use as bonsai and will need to be cut back and started over.
Don’t keep messing with your tree! Any pruning will slow its growth and make the trunk diameter smaller. When you think about how much growth a tree has, keep in mind that its trunk will get thicker and it will put out more growth next season.
Winter pruning should be the only time you need to do it to control or redirect the trunkline, depending on how you want the finished trunk to look. (An article on developing field-grown tree trunklines can be found here).
Rootpruning your field grown trees will slow down their growth rate and negate the purpose of field growing. But it is important to build up the future nebari and root structure. If you don’t, your fat field-grown trunk could be ruined by a bad nebari.
Rootpruning should be carried out in early Spring as with bonsai. Roots should only be pruned to encourage a good nebari. Every second or (preferably) third year, lift the tree and examine the root structure. Any roots close to the trunk that aren’t good for future use can be cut off. This includes roots that cross, roots that grow at an angle from the trunk that isn’t good, a thick root that is too dominant, and roots that are very straight and don’t branch or taper much. Unless you planned ahead and planted the tree on top of a tile, you should also cut off or remove any roots that grow downwards. One year, try to cut off as few roots as possible and no more than two big ones.
Cut around the tree’s base with a spade in early spring the last year or two before you finally lift it to start bonsai training. This will help the roots grow closer to the trunk.
Bonsai is the ancient Asian art of cultivating miniature trees in containers. The practice originated in China over a thousand years ago and was later adopted in Japan where it evolved into a revered art form. At the heart of bonsai is the use of techniques like pruning wiring and potting to artistically shape plants to create elegant living sculptures that mimic nature.
While bonsai trees are grown in pots and trays for most of their lives, many bonsai artists also utilize periods of ground growing. Planting bonsai specimens temporarily in garden beds or fields allows them to grow freely and develop trunks, branches and roots more rapidly. This enables creating bonsai with impressive proportions and details that would be difficult to achieve with container growing alone.
Ground growing can be a valuable technique for bonsai enthusiasts who have the space and patience This guide covers the benefits of field growing bonsai trees, which species work best, timing, care tips and transitioning them back into containers.
Why Grow Bonsai Trees In the Ground?
Growing bonsai in the earth provides several advantages over restricting their roots to life in pots and trays. Benefits of ground planting bonsai trees include:
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Faster trunk thickening and taper – With their roots unconfined, trees send more energy into trunk and base growth The trunks flare outwards more rapidly at the base and taper upwards.
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Coarser trunk texture – The bark also matures faster and takes on a more rugged, aged appearance.
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More extensive branching – Unrestricted by a container, the branching can extend freely and profusely. More options to select branches for the final design.
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Bigger foliage and blooms – With more access to nutrients and moisture from the soil, the leaves, needles and flowers develop larger.
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Quicker recovery from work – Trees bounce back faster from heavy pruning, root work and repotting when ground grown. Growth is more vigorous.
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Improved health – Time rooting freely in the ground restores vitality compared to life in a pot. Stress and circling roots are reduced.
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Cold protection – The surrounding earth insulates the roots from temperature swings better than container culture does.
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Developing stock – Young plant material progresses quickly into pre-bonsai suitable for training.
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Informal upright style – Achieving convincing taper and movement for this style is easier when field growing trees.
The unrestricted space allows bonsai to flourish and progress more rapidly towards their design potential.
Which Species Are Best For Ground Growing?
While most trees suitable for bonsai could benefit from periods growing in the ground, some types react especially well. Some of top choices include:
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Deciduous trees – Maples, elms, oaks, beeches, hornbeams etc thrive with free root space.
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Evergreens – Pines, junipers, cedars, spruces and firs also grow vigorously this way.
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Flowering trees – Cherries, crabapples, azaleas and other flowering specimens progress quickly.
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Tropicals – Bougainvillea, ficus, buttonwood and fukien tea can grow very fast when ground planted.
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Shrubs – Many shrubs like boxwood, jasmine and rosemary grow rapidly to develop as bonsai.
It’s best to avoid specimens like bonsai that dislike root disturbance. But most trees appreciate the chance to stretch out underground.
When Is The Best Time For Ground Growing Bonsai?
Ground growing bonsai trees works best during certain parts of the year:
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Early spring – Plant in early spring to allow the roots to grow freely all season. Avoid frost risk.
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After repotting – Ground planting right after root pruning in spring helps generate new feeder roots.
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Summer – Warm months encourage fast progress above and below ground.
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During trunk training – Maximize caliper thickening by letting trees grow unchecked.
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After major work – The ground fosters quicker recovery from heavy bending, pruning etc.
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Overwintering – Insulates roots better than wintering in containers.
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Developing stock – Planting young trees as pre-bonsai accelerates their growth.
Avoid planting weakened trees in the heat of midsummer. Otherwise any time is fair game for growing bonsai in the ground.
How Long To Leave Bonsai Trees In The Ground?
The ideal duration for a bonsai tree to remain growing in the ground depends largely on the purpose:
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Trunk development – 1 to 6 years allows impressive thickening. Monitor taper regularly.
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Root regeneration – Repot after one full growing season of root recovery.
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General health – 6 months up to 1-2 years restores weakened trees to vigor.
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Overwintering – Leave in the ground for winter then pot up in early spring.
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Pre-bonsai – Young stock often grows in the ground for 3-10 years depending on the goal maturity.
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Flowering – 1-3 years maximizes blooms on flowering tree varieties.
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Evergreens – 2-4 years helps pines and other evergreens gain volume.
It’s best to limit time in the ground to the minimum needed. Evaluate growth periodically to determine when it’s time to pot up bonsai trees.
How To Plant A Bonsai Tree In The Ground
Follow these tips when planting bonsai trees directly in garden beds or growing fields:
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Select a sunny, sheltered spot with good drainage and fertile soil. Amend if needed.
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Carefully remove the tree from its pot without excessive root damage. Comb out circled roots.
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Dig a hole a little wider than the root spread, keeping the depth the same as it was growing in the pot.
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Backfill around roots with a blend of native soil and coarse material like grit. Eliminate air pockets.
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Water thoroughly after planting to remove air and settle the soil. Stake tall trees if necessary.
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Apply organic mulch around the base to retain moisture and suppress weeds.
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Monitor surface roots emerging over time and cover again with soil.
Caring For Bonsai Trees In The Ground
Meeting basic care needs is vital for bonsai trees growing in garden beds:
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Water whenever the top few inches of soil become dry. Increase frequency during hot, dry weather.
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Continue fertilizing as normal, preferably with organic slow release formulas worked into the soil.
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Monitor for pests and disease and take preventative and curative actions promptly when found.
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Perform any needed pruning and shaping to maintain design and vigor. Restrain leggy growth.
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Protect trees from deer, rodents and other wildlife with fencing if they are likely to browse.
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Cover large pruning wounds with cut paste to prevent dieback when eventually potted up.
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Weed regularly to prevent competition especially when establishing newly planted trees.
With attentive care, bonsai thrive in garden bed growing conditions and progress rapidly.
Transitioning Bonsai Trees Back Into Pots
When it’s time to return ground grown bonsai trees to life in containers, proceed gently to minimize transplant stress:
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Do major pruning of branches and roots during the dormant season before buds swell.
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Carefully undercut and lift trees from the ground with minimal damage to small absorbing roots.
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Pot up into an oversized container to accommodate the larger root system.
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Use a free draining bonsai soil mix amended with nutrients to encourage recovery.
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Prune back the foliage by around 1/3 to balance the reduced roots.
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Water frequently at first to eliminate air pockets and settle roots until regrowth signals they have adjusted.
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Protect newly potted trees from intense sun and wind which aggravate moisture loss and transplant shock.
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Be prepared to nurse trees through the transition with careful watering, humidity, etc until stabilized.
With an attentive hand during planting and aftercare, bonsai trees quickly adapt back to pot culture.
The Advantages Of Ground Growing Bonsai Trees
When used judiciously, growing bonsai trees in garden beds and fields can provide a range of benefits:
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Dwarfing mature looking specimens faster than container culture alone allows
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Developing convincing trunk girth, movement and bark complexity
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Generating abundant branches to design an ideal silhouette
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Restoring vigor into stressed or root-bound bonsai trees
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Creating pre-bonsai stock more rapidly from seedlings or young whips
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Protecting roots from winter damage while overwintering plants
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Achieving a flowing informal upright style which appears aged and weather
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FAQ
Can you put a bonsai tree in the ground?
Can I plant a bonsai tree in regular soil?
What happens if you plant a bonsai tree outside?
How long can a bonsai tree stay in a box?
Can you grow bonsai in the ground?
You can grow any species of bonsai in the ground, so long as it is able to survive in your climate it will be fine. It can also be at any age and at any stage of its bonsai journey. Young trees are going to be the best trees to plant in the ground to grow as bonsai and are the most common trees to do this technique on.
Can a bonsai tree grow out of control?
This can help you avoid mistakes that can lead to your tree growing out of control. If you plant a bonsai in the soil, it can easily grow out of control, turning into a full-sized tree. The best way to grow a bonsai in the ground is to start it from a seedling, which has an extremely thin trunk.
What is bonsai gardening?
Bonsai gardening is a unique horticultural practice that combines your passion for nature with the artistic expression of shaping and training trees. It involves the careful cultivation of young saplings or plants in the ground for a few years, before they are uplifted and placed in suitable containers for training.
Will a bonsai grow into a full size tree?
A bonsai will try to grow in to full size tree if you let it. One of the main reasons a bonsai stays so small is due to the limited growing space they have in a small pot. Once you plant a tree in the ground this space restriction is removed and they will quickly start to stretch out and take advantage of the endless room available to them.
How do bonsai trees grow in Japan?
In Japan you will often see bonsai trees grown in the ground in a mound. Instead of building a grow bed structure to place the soil in, they just mound up the soil and place the trees into this mound. It’s the exact same as a grow bed, just without the retaining walls.
How do you grow a bonsai tree in the ground?
Growing bonsai in the ground can be as simple as digging straight into the ground, or you can set up a raised grow bed. You can build these grow beds with planks of wood in same the way that you would see another other raised grow beds in other forms of gardening. Using a grow bed allows you to control the soil that the bonsai tree sits in.