Overwintering potted plants is always a challenge for gardeners. You need to know a lot of tricks to succeed.
QUICK ANSWER: A potted Japanese maple can survive the winter outdoors in zones 7-9 without any problems. In this case, you do not need to do anything about it. When planted in a container, this tree can survive to 5°F(-15°C).
But if you want your maple to be more comfortable through the winter, stick to the following recommendations.
Tips for successful winterizing of a potted Japanese maple in zones 7-9
- Avoid fertilizing potted Japanese Maple later than June. This is especially true of slow-release fertilizers. Late feeding can prevent the tree from going into winter dormancy.
- Move the pot with the tree to a place without frost drafts. This can be behind the house or near a large evergreen tree.
- Water the maple tree well in late fall before frost begins. Give it a good soaking, but make sure the excess water gets out through the drainage holes.
- Mulch the surface of the soil in the pot with organic material. For example, it can be pine bark or wood chips. However, do not bury the trunk in the mulch.
In the 5 and 6 USDA hardiness zones, potted Japanese maples need sheltering and other actions to protect them from cold temperatures. You will learn more about this in the following chapters.
Japanese maple in container zone 5
Zone 5 is the northernmost area where you can grow Japanese Maple in a pot. Temperatures can drop to -10°F (-23°C) in this zone, which the maple roots cannot withstand. So you need to be sure to protect it.
The first and the best thing you can do is to move the potted maple to an unheated room. A cold garage meets this requirement well. It can also be some other building that is not heated in winter.
Move the potted Japanese Maple to the garage when the outside temperature drops to 28°F (-2°C). By this time, the maple will be dormant and will not even feel the change in the environment.
Japanese maple in container zone 6
Winter is milder in zone 6, but the roots of the potted maple will still be uncomfortable outside. You don’t have to bring it indoors, but you do need to protect it.
The first thing to do is to move the tree to a more wind-protected location. This could be between two buildings or between two large trees. Some low places with no wind drafts are also good choices.
The second thing to do is to protect the roots. The best way is to bury the pot in the ground for the winter. The heat from the ground will prevent damage to the roots.
Do not bury the pot too deep. The edge of the pot should be at ground level. Also, do not put soil on the trunk of the maple.
Another way to protect the roots is to put the pot on a flat surface and bury it in organic material, something like a volcano mulching. You can, for example, use compost for this purpose. Like in the first case, you don’t need to cover the tree trunk, just the pot.
Can you bring a Japanese maple indoors for winter?
You can not bring a potted Japanese Maple indoors when discussing a heated room. Too high a temperature will prevent the tree from entering a dormant state and severely deplete it.
In addition, there is not enough humidity in the house. This can lead to leaf damage or even the death of the tree.
And lastly, while remaining active, the maple needs enough direct sunlight. It is unlikely to achieve such sun exposure in the house.
The only suitable place for overwintering indoors is an unheated room. A garage or some other building with no heating is best. Do not take the maple there until the temperature has dropped below 28°F (-2°C).
Should I cover my potted Japanese maple in winter?
You don’t have to cover a potted Japanese Maple for the winter. Putting a blanket over the top of the maple won’t do much good because the top part of the tree is quite frost-resistant.
A blanket will only put extra weight on the branches. During heavy snowfall, the branches will break.
All you have to do is move the maple into the garage for the winter if you live in area 5. Or protect the root system if you live in zone 6.
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If I live in Zone 3 which the temperature can sometimes drop to -30C to -32C (last for a few days) and what should I do with my Japanese maples planted in the ground and in the pot?
1) Can I put my potted maples in an insulated but not heated garage? Or better in a shed?
2) Can I use bubble wrap to wrap my young maples tree (planted in the ground) and covered with a plastic garage bag with heavy mulch? Do I need to water it in winter?
Please advise through email and much appreciate for your help!
Hey Dennis, in response to your questions:
1. It’s best to use an unheated garage.
2. Avoid wrapping the maples with plastic. Opt for breathable materials like jute burlap or a frost blanket designed for trees.
3. Refrain from watering during the winter, unless it’s an unusually warm and dry season.
We put slow-release fertilizer on my baby potted Japanese Maple now (October). Now I realize that was a mistake. Will it probably die this winter? We’re in zone 7. Is there anything we can do to save it? I wanted to transplant it to ground in Spring. Also, what is the minimum size my tree should be before transplanting it to ground?
Hi P. Clevenger. As far as I know the shell of the slow release pellets will only dissolve in warm weather, but not in cold weather. They will most likely remain dormant until next spring.
Keep the maple in a cool place all winter. For example, a garage that doesn’t freeze but isn’t heated. Next spring, plant it in the ground. It is best to plant maples that are at least 8 inches tall in the open ground.
For a potted dwarf Japanese Maple tree in a pot, is there a level shown on a soil tester I can go by to make sure it is wet enough
Hi Nancy,
Yes, a moisture meter (soil tester) can be a great tool for monitoring the moisture level in the soil of your potted dwarf Japanese Maple. These meters usually display levels on a scale of 1 to 10 (or sometimes 0 to 10), where:
1–3 = Dry
4–7 = Moist
8–10 = Wet
Can i put down inselation and cover them with a white plastic berrel im in maine ty
Hi Bill,
I don’t recommend covering the maple with plastic. It’s best to wrap it in a breathable frost protection material.