How thirsty are Japanese Maples? Ensuring your tree gets the right amount of water is one of the most important ways you can help it thrive and grow. And striking the right balance between overwatering and underwatering depends greatly on local conditions. Regional variations in temperature and rainfall can make a big difference, as can the drainage of your soil. Our guide will tell you when, how, and how much to water your Japanese Maple to ensure it’s in optimal health.
Japanese Maples need more water when they’re first getting established. They’ll also be much thirstier in the summer heat than during the cold and wet of winter. You should test the soil periodically and water your Japanese Maple thoroughly when the top few inches feel dry.
As you get more practice watering your tree, you’ll learn to tell when conditions are dry enough that it needs a drink. This post will explain how to spot problems like overwatering, underwatering, overly dry or marshy soil, and poor water quality. Try not to worry too much, though — hydrating Japanese Maples properly isn’t as hard as you might think. All it takes is a little basic know-how.
Do Japanese Maples Need a Lot of Water?
The answer to this question is complex because a Japanese Maple tree’s watering needs change throughout its life. As the tree matures, its roots become more established and spread further out, increasing its ability to seek out moisture. A mature Acer Palmatum in an area with decent rainfall may hardly ever need you to water it. When it’s young, though, the root ball is much more confined, and your Japanese Maple requires more irrigation.
A newly planted Japanese Maple needs around 10 gallons of water per week. Note that this is just a rule of thumb that comes with some important caveats:
- Not all of that moisture has to come from the hose. There’s no need to water your Japanese Maple immediately after heavy rainfall.
- Seasonal temperature variations also make a big difference. You can cut back on watering in the fall, and your tree may not need any irrigation at all in the winter.
- You have to consider the soil quality as well. Dry, coarse, sandy soil will dry out much faster than heavy clay.
- If you’re applying synthetic fertilizer to your Japanese Maple, you may need to water it more deeply and frequently than usual. The tree will likely grow faster and use more water, and watering thoroughly helps avoid a harmful fertilizer buildup.
Once your tree has been planted in the same spot for two or three years, its roots should be well-established. At that point, you can ease up on watering it a bit. Instead, monitor its health and environment and give it a drink when conditions are particularly dry.
Water the Soil, Not the Tree
It’s often best to think in terms of how moist the ground is rather than how much water you’re adding. Japanese Maples are happiest when the soil around their roots is moist but not wet. If it stays too damp for too long, there’s a major risk of root rot (see below for more on this).
While your tree is still young, test the soil with your finger or a moisture probe every two days in the spring and summer. When it feels damp, give it a soak. Lots of gardeners employ the “screwdriver test” — pushing the tip of a Philips-head screwdriver into the soil. If it’s damp enough, you should be able to sink it 6-8 inches deep. When you can’t do that, it’s likely time to water.
In the fall, you can check the soil every three to five days instead of every other day. And in the winter, it’s usually fine to stop watering entirely unless the weather gets very dry.
Once your Japanese Maple is well-established, you’ll likely need to water it only during the hottest, driest weeks of summer. Watch for wilting leaves and check for dry soil, but leave the tree alone if these signs are absent. The same rules described above apply here: water only when the top 2 inches of soil feel dry.
How To Water Your Japanese Maple
Periodic deep drenches are better for your tree than small, frequent sips. Watering deeply gives a Japanese Maple incentive to grow deep roots. And giving the soil some time to dry out between waterings reduces the danger of devastating fungal infections.
A good general guideline is to give your maple tree 2-3 gallons of water in one sitting. Apply this in a long, slow, steady soak. Ideally, you want the water to permeate roughly 6-8 inches below the ground. Then let the soil dry out for at least a day or two before watering again.
For most of your Japanese Maple’s life, you should water it only out to the drip line (the spot where water drips off the outermost branches). The majority of a mature tree’s roots fall within this zone, so irrigating further out may be a waste of water. But for the first couple of years after planting, you can and should extend your watering zone a few feet past the drip line. This will help encourage the roots to spread out and create a nice wide base.
Avoid watering within a foot of your Japanese Maple’s trunk. Wet bark may get infected. It’s also best not to splash the leaves if you can avoid it. Damp leaves can also get fungal infections, and on hot days, beads of moisture can focus the sun’s rays and increase the risk of scorching.
The best time to water your Japanese Maple is in the early morning. This reduces the chances that any water droplets on the leaves will get burned because they’ll likely evaporate before the sun is high. It also means your tree can start absorbing the water right away as the day heats up, instead of sitting in wet soil all night.
Tools For Watering a Japanese Maple
The simplest way to hydrate your Japanese Maple is with a garden hose on the “soaker” setting. This allows the water to slowly permeate the ground instead of splashing off the surface and quickly evaporating.
A drip irrigation line requires a little more setup but involves less day-to-day effort once it’s in place. Lay it out in a slowly widening spiral, moving out from the base of your Japanese Maple. Don’t place it right against the trunk, and don’t leave it on constantly. You’ll still want to space out your watering sessions to give the soil a few days to dry out in between them.
One other DIY option that comes highly recommended: the bucket method. Buy yourself a bucket that can hold a few gallons of water and drill a small hole in it. Fill it with water and set it near your Japanese Maple. Then let the water slowly dribble out. You might want to move the bucket every so often to spread the water around to different sections of the root system.
Lawn sprinklers are usually not the best method. They tend to splash the foliage, which can raise the odds of a sunburn or a fungal infection.
What’s the Best Kind of Water to Give Your Japanese Maple?
In the vast majority of cases, it’s fine to water your Japanese Maple with whatever comes out of your tap. The small quantities of additives like fluoride and chlorine in municipal water won’t make a difference to your tree. However, if you live in an area that has particularly hard water, you might want to look into alternatives.
If you don’t know the term, “hard” water has a high concentration of minerals such as calcium and magnesium. In small quantities, these won’t hurt a Japanese Maple and can actually provide a bit of added nutrition. But if there are a lot of these minerals, they can build up in the soil and dehydrate the roots.
The best indicator that this is happening is that the leaves are drooping and turning brown or black at the tips even though you’re giving your tree plenty of water. (Though this can also be due to overwatering or problems with your Japanese Maple’s fertilizer dosage.) A whitish crust building up on the soil and/or the leaves can also hint at an excess of minerals.
Unfortunately, commercial “water softeners” don’t help — in fact, they tend to make the situation much worse. These products contain large amounts of salts, which make hard water taste better but are terrible for Japanese Maples.
Gardeners living in hard-water areas have a few options:
Collect Rainwater
Rain is arguably the best water for Japanese Maples — it’s low on minerals, contains a tiny bit of organic nutrition, and generally has a slightly acidic pH. Storing it up in a rain barrel lets you give your Japanese Maple some relief during dry spells. It may be hard to store enough rain to completely replace the need for irrigation, but it can help.
Use A Filter
Some types of water filters can remove minerals from your water on the way to your tree. This deionizing filter is fairly affordable and easy to attach to a hose. It’s designed to let you wash your car without leaving water spots, but it also works for your garden. However, it has a limited lifespan and may work best with a low flow rate and pressure.
It’s also possible to attach a reverse osmosis filter system to your hose. This is a more permanent setup, but it comes with some drawbacks of its own. An RO filter will produce quite a bit of wastewater that’s quite high in minerals and other contaminants. This is somewhat inefficient and requires you to figure out a place to dump it. If you’re interested in trying it, here’s a helpful tutorial.
Buy Filtered Water
Another way to avoid giving your Japanese Maples hard water is to simply buy pre-filtered water in bulk. You can then apply it using a watering can or simply pour it slowly and steadily from the jug. Keep in mind that not all types of filtration remove the minerals from water, and some companies actually add them back in for taste. Look for distilled or RO water that’s not mineral-enriched.
How To Know If You’ve Overwatered Your Japanese Maple
For an established Acer Palmatum growing outdoors, overwatering is generally a bigger threat than droughts. Your tree’s roots need oxygen, which they can’t absorb when the earth around them is constantly saturated. Sludgy soil is also a bonanza for pathogenic fungi and bacteria. A Japanese Maple with “wet feet” may develop root rot as these microbes multiply.
The surest way to tell if your tree is overwatered is to keep a close watch on the soil. Think of it like a dessert: between waterings, the ground should feel moist like a cake, not wet like a pudding or dry like a cookie. But if it stays saturated for more than a day or so after watering, you have one of two problems:
- You’re watering too often, and the soil isn’t getting a chance to dry out.
- Your soil has poor drainage.
Aside from swampy soil, signs of an overwatered Japanese Maple can include:
- Limp, yellowing leaves, possibly with brown tips
- Dull color
- Slow or nonexistent growth
- Leaves dropping/thinning foliage
Note that some of these problems can also be caused by underwatering, hard water, or too much fertilizer. Diagnosing it may require thinking critically about your care habits. Is there something you’ve given your tree too much or too little of?
It may also be a good idea to dig up a small patch of soil around some of the roots and see if they show signs of rot. Infected roots may be dark brown, black, or gray instead of a healthy light brown. They often have a slimy surface and feel mealy or squishy when you poke them. It might also be possible to spot large clumps of fungal growth among the roots.
Treating Root Rot In An Overwatered Japanese Maple
There’s a limit to how much you can do about root rot in Japanese Maple that’s well-established in the ground. Uprooting a mature tree to clean the roots is likely to hurt more than help. Your best bet is to simply let the soil dry out and hope that your Japanese Maple is vigorous enough to fight off the infection. Consider removing any mulch around the tree to allow for more rapid evaporation.
If your Japanese Maple is in a container, you can take it out and prune away the rotten roots. Disinfect your pruning shears with rubbing alcohol between snips to avoid contaminating healthy tissue. Discard all the old soil, sanitize the pot, and replant your Japanese Maple in brand-new potting mix.
You may be able to do something similar with an in-ground Japanese Maple if you only planted it recently. It may be a good idea to treat the soil with a fungicide, but even after doing this, you should consider finding a new site for your tree. Root rot often means the spot you’ve picked isn’t draining well.
If the soil in your garden is too dense and water-retentive all over, you can reduce the risk of overwatering by replanting your Japanese Maple in an elevated mound. See this article for instructions.
How To Tell If Your Japanese Maple Is Thirsty
Though overwatering is a bigger threat, you don’t want to dehydrate your Japanese Maple either. How do you know if this is happening?
The symptoms are very similar to the signs of overwatering described above. However, underwatered leaves are likely to feel crispy and dry rather than limp and soft. Environmental conditions may provide an even better clue — in dry, scorching summer weather, underwatering is common and overwatering is rare.
You can also check the soil. The screwdriver test described above is helpful here too. Dry, hard-packed earth tends to stop you from getting the point in very far. Combined with discolored, drooping leaves, this is a pretty good hint that your Japanese Maple needs water.
How to Fix an Under-Watered Japanese Maple
The solution here is pretty straightforward: water your Japanese Maple. A nice thorough soak should get your tree looking happy again. The dead leaves won’t come back to life, and the damaged ones won’t heal, but the wilting should stop. Next year, the dead stuff will be replaced by fresh, healthy growth.
This can get a bit trickier if the ground has died out enough to become hydrophobic (water-repelling). This can happen with soils containing a lot of sand. It may also be due to an abundance of poorly composted organic matter. When water hits hydrophobic soil, it tends to bead up and roll away instead of getting absorbed.
There are a few ways to get water into hydrophobic soil:
- Use a wetting agent. Mix a hydrophobic substance into your watering can, such as a few drops of gentle liquid soap. This helps the water droplets break up and trickle into the earth.
- Drip watering. A slow, steady trickle of water can gradually overwhelm the soil’s resistance. A drip irrigation system is a good choice here. The “bucket method” described above or a long drench from a hose with a
soaker nozzle may also do the trick. - Mulch. Laying down a layer of organic mulch can help lock water in place instead of letting it run off or evaporate. This gives it time to soak into the soil.
- Amend the soil. This is more of a long-term fix, but it can help avoid this problem in the future. Adding some clay or well-composted organic material to the soil can make it less likely to get hydrophobic in the future. Remember to pair this with thorough irrigation. If you fertilize your Japanese Maple with compost, make sure to water it well during the subsequent growing season.
Watering Japanese Maples In Containers
Some gardeners like to grow Japanese Maples in pots rather than planting them in the ground. This can make a substantial difference in your tree’s watering needs.
For one thing, you may have to water your Japanese Maple more often, since there’s less soil to store moisture. You should still follow the advice above about checking the soil and watering only when it feels dry but be prepared for your plant to need more frequent soaks.
Paradoxically, your Japanese Maple is also more vulnerable to overwatering in a pot. Moisture can build up to unsafe levels more easily without an entire lawn or garden to soak it up. You should make sure that your Japanese Maple’s pot has at least one big drainage hole in the bottom. Consider placing it right on the ground instead of on top of a drip tray. And make sure to use a coarse but fluffy potting mix with excellent drainage.
Remember that when you grow your Japanese Maple in a container, it will never get “established” the way it would in your garden. The tree can’t stretch its roots out and hydrate itself using groundwater. So check the soil for dryness as often as you would with a newly planted Japanese Maple.
Final Thoughts
Lengthy articles like this one can make proper watering seem very complicated. But remember that you may not need to water your Japanese Maple much at all once it’s firmly rooted in your landscape. For those first couple of years after planting, pay close attention to the soil and stick with the advice above. This should help you keep your Japanese Maple hydrated, happy, and healthy.