How much and how often should you fertilize your Japanese Maple? Adding nutrients to ornamental trees can be a delicate process. Fertilizing too much, too little, or at the wrong time may hurt your plant rather than helping. This guide will help you understand how much fertilizer your Japanese Maple needs, as well as when and how to apply it.
You don’t need to fertilize your Japanese Maple during its first year after planting. After that, you can add a light dose of slow-release fertilizer in the early spring. Avoid high-nitrogen or fast-acting formulas, which can promote unattractive and unhealthy growth.
Japanese Maples aren’t known for being particularly heavy “feeders”, so it may not be necessary to fertilize them every year. But if your tree is struggling to grow, or a soil test reveals a deficiency, it’s a good idea to supplement its diet. We’ll give you some tips on how to do so, and we’ll explain how to tell if you’ve overdone it. Read on for our detailed guide on how to fertilize Japanese Maples.
Why Fertilize Your Japanese Maple?
With indoor plants, fertilizing is always a necessity. The cramped environment of a pot lacks the many nutrient sources found in the great outdoors, like animal manure, decomposing vegetation, dissolving rocks, and rainwater. But that’s not true of the soil in your lawn or garden, so why is it necessary to fertilize your Japanese Maple?
Well, the dirty little secret is that it may not be. Unlike some plants, which are greedy nutrient sponges, Japanese Maples can often get by without much added nutrition.
On the other hand, not every home is blessed with equally fertile soil. Some areas have shortages of particular nutrients due to particularities of the local geology, climate, and ecosystems. And if your land has already been used to grow lots of ornamental plants or food crops in the past, a fair amount of its natural fertility may have been depleted.
Some types of soil amendments may also make it easier for your Japanese Maple to absorb the nutrients it needs. While this may not exactly be considered “fertilizing”, it definitely makes your land’s fertility more accessible to your tree. This can help boost its growth and improve its health.
What Age Should You Fertilize Your Japanese Maple?
Wait at least a year after planting your Japanese Maple before giving it any fertilizer. It will likely already have some nutrients in its soil from the nursery. Until the root system has some time to establish itself in the ground, it won’t be able to do much with extra nutrition.
If you fertilize your tree too young, the best-case scenario is that you’ll be wasting your time. A much less pleasant possibility is that the excess of salts in the fertilizer could damage the roots.
Mature Japanese Maple trees — those which have been growing for 10-15 years — may also not need much fertilizer. By that point, they should have wide, deep root systems with thriving colonies of beneficial fungi and bacteria. A mature tree should be well-equipped to draw nutrition from the ground. At most, it might need to be supplemented with fertilizer every few years.
The sweet spot for fertilizing a Japanese Maple is between 2 and 10 years after planting. That’s when the tree is growing fastest and some extra nutrition is most likely to improve its vigor and health.
When Is The Best Time To Add Nutrition?
Early spring is the ideal time to fertilize your Japanese Maple. This ensures that it’s getting its dietary supplement just as it’s getting ready for a new season of growth. That way, you can be sure your plant won’t be pushing out weak, malnourished branches and leaves. Give your Japanese Maple some fertilizer just as it’s beginning to leaf out for the season.
If you miss the very start of the growing season, it’s not the end of the world. You can typically apply fertilizer safely right up to the end of the spring.
The key thing to avoid is giving your Japanese Maple any added nutrition as the fall is settling in. This is particularly risky with nitrogen-heavy fertilizers. Your tree will often funnel those extra nutrients into heavy leaf production. This can delay its preparation for winter and leave it vulnerable to frost damage and dieback. It could also put a damper on your Japanese Maple’s normal flush of autumn color.
Note that the timing here depends somewhat on the type of fertilizer you’re using. Liquid fertilizers that release all their nutrients in a rapid burst can be used up to the end of summer. However, slower-acting fertilizers are typically better for Japanese Maples — see below for the reasons why.
What’s The Best Fertilizer For Japanese Maples?
How can you pick the right fertilizer to set your Japanese Maple up for success? By remembering the following guidelines:
Easy On The Nitrogen
When choosing a fertilizer to use with your Japanese Maple, pick one with a relatively low nitrogen content. Acer palmatum is a naturally slow grower, and working with its natural rhythm will produce the healthiest development.
Adding large amounts of nitrogen can sometimes prompt the tree to shoot up and out very quickly — at the expense of its overall health. The plant essentially gets “stretched”, producing very thin walls that are more susceptible to cold and disease. Nitrogen-boosted growth may also look cramped and spindly, messing up the graceful look of the tree.
Not sure about the nitrogen content of a given fertilizer? Look for the NPK numbers — usually represented on the packaging as three numbers separated by dots or dashes. They represent the percentage of the three most vital plant macronutrients, nitrogen, phosphorus, and potassium (in that order). That first number, the N value, should generally be 15 or lower, and it definitely shouldn’t be higher than the other numbers.
What if you get compost from your backyard, manure from your neighbor’s farm, or another all-natural source of fertility? Organic fertilizers can vary a lot in terms of their actual nutritional content. But in general, animal products like fish emulsion, blood meal, and manure are too high in nitrogen to make fertilizer for your Japanese Maple. Homemade compost should be safe — it’s a fairly weak nutrition source, but your tree doesn’t need much anyway.
Low Dosage
A light touch is best when fertilizing Japanese Maple trees. You can generally go with a fairly mild, balanced, all-purpose formula. A fertilizer with an NPK number of about 10-10-10, like this one, should be perfect. If you use a stronger formula, cut the dosage down to ½ or ¼ of what the package recommends.
Don’t worry about buying a special “Japanese Maple fertilizer”. The idea that specific plants need specially-formulated fertilizers is mostly a marketing trick. And many of the nutrient blends targeted at Japanese Maple owners are too weak to accomplish much. It’s definitely better to use a fertilizer that’s too weak rather than one that’s too strong, but a 4-3-4 NPK ratio isn’t going to give your tree much extra help.
Slow-Release
Synthetic fertilizers come in two basic types. First are the fast-acting ones, usually available in the form of a liquid or a powder. You mix them in with your water to provide a quick flush of nutrition all at once.
The others are “slow-release” or “controlled-release” fertilizers. These are generally small pellets that dissolve gradually, releasing nutrients into the soil a little bit at a time. As a rule, this is the type we recommend for Japanese Maples. Slow and steady nutrition fits the growth style of these trees perfectly. A large amount of fertilizer all at once may cause the type of unhealthy growth spurt we warned about above.
The one exception is if your Japanese Maple is suffering from an urgent nutrient deficiency and its health is clearly suffering. In that case, it’s a good idea to give it some fast relief with a liquid all-purpose fertilizer. Otherwise, stick with the granular style.
Many slow-acting fertilizers will list their release timeline on the packaging. For a Japanese Maple, you’ll typically want to pick a type that dissolves over 4-6 months. If it takes longer than that, the tree may still be receiving added nutrition in the late fall. This could interfere with its winterization.
How To Fertilize Your Japanese Maple
Once you’ve chosen the fertilizer you want, how should you give it to your tree? In most cases, the process is fairly simple. Granular fertilizers can generally be scattered in a wide band around the base of your Japanese Maple. Start about a foot from the trunk and extend to one and a half times the width of the canopy.
Usually, nutrients will simply trickle down to the feeder roots as you water. However, if your soil has poor drainage or is compacted and prone to runoff, you may need to bury the fertilizer, so it doesn’t wash away.
In that case, you can dig a few holes in an even ring around the tree for the fertilizer pellets. They should be 6-8 inches deep and at least 1 foot from your Japanese Maple’s trunk. Divide the fertilizer evenly between the holes, then fill them in.
If you do this once per year in the spring, your growing Japanese Maple should have plenty of nutrition!
During any growing season in which you fertilize your Japanese Maple, make sure to give it plenty of water. Frequent, thorough watering helps to make sure that the fertilizer flows into the soil at a healthy pace. This helps the nutrition reach the roots and reduces the risk of a damaging buildup of salts. Check the soil every few days, and when it feels dry, give it a good soak. This is especially important as the weather starts to heat up.
Did You Overfertilize?
The biggest risk with applying fertilizer is overdoing it. The salt compounds that nourish your Japanese Maple can hurt it if they get overly concentrated in the soil. Excess fertilizer interferes with the osmotic pressure that enables the roots to take in water (and, ironically, nutrition). This can cause a condition known as fertilizer burn.
This typically manifests as shriveled brown or black leaf tips and edges. In extreme cases, the tree may rapidly lose leaves due to rapid dehydration.
Fertilizer burn is rare with granular fertilizer, but it can happen if you misjudge the dosage. If you think that you’ve given your Japanese Maple too much fertilizer, there’s not much you can do except try to rinse some of the salts out of the soil with an extra-heavy watering. Next year, cut your dosage back substantially or avoid fertilizing at all.
Does Your Japanese Maple Need More Fertilizer?
Underfertilizing is much less dangerous for a Japanese Maple than going overboard. However, it could slow or stunt your tree’s growth. Severe cases of malnutrition can cause misshapen leaves and limbs or discolored foliage.
You can usually tell whether your Japanese Maple could use some added fertilizer by paying attention to its growth. An Acer palmatum that hasn’t yet reached maturity will typically gain one or two feet in height each year. (Though the exact rate can vary a lot depending on the variety of Japanese Maple you’re growing, as well as how much sun and water it gets).
If it’s struggling to reach that growth rate, you might want to add a bit more nutrition the following season. Abnormally small leaves are another possible sign that your Japanese Maple needs fertilizer.
More severe nutrient deficiencies can cause bark lesions, branch dieback, and misshapen or off-color leaves. Don’t jump straight to adding fertilizer when you see these symptoms, though. You should check for issues like dehydration, pests, or sun scorch first.
Nutrient deficiencies can also be due to pH problems. The best soil for Japanese Maples has a pH of around 5.5. If it’s much higher or lower, the roots may not be able to access the chemicals your plant needs to grow.
Sample Your Soil
A soil test can often reveal whether your landscape is short on nutrients that your Japanese Maple needs. It’s usually best to have this done by a professional laboratory. They can test for the full spectrum of nutrients a plant requires, as well as offer tailored recommendations for amending your soil.
You can often find a soil lab by checking with local, state, and agricultural colleges in your area. They’ll often have testing facilities that will analyze your soil — sometimes for free, or for a very negligible cost. Alternatively, you can use a mail-in kit like this one.
Collect soil for your sample from a few different spots around your garden or lawn. If it’s only a smaller area you’re worried about, 5 or 6 samples should be fine. To test an entire lawn, you’ll want 10-15. Avoid spots where there’s reason to think the chemical composition is unusual, such as near plants where you’ve recently applied fertilizer.
In each sampling spot, remove any plants or other debris from the soil surface first, then dig down to around 8 or 12 inches and take roughly ½ an inch of earth from the inside of the hole. Let your samples dry at room temperature and mix them together, breaking up any clods. Then take about a pint of the resulting blend for testing.
How exactly you submit it will depend on what soil lab you’re using. But once you get the results, you’ll know if your soil is lacking in any important plant nutrients and if the pH is appropriate for Japanese Maples.
Fertilizing Japanese Maples in Containers
What if you’re growing your Japanese Maple in a pot instead of a hole in the ground? Actually, most of the advice above applies just as well in this scenario. You should still fertilize lightly, waiting until a year after transplanting, and generally in the early spring.
The main difference is that a Japanese Maple grown in a container will always need fertilizer eventually. While a tree in rich soil may be able to nourish itself without outside assistance, you’re the only source of nutrition for a potted plant. We’d still advise going with a mild, balanced, slow-release formula, applied annually as the tree is forming leaves.
Final Thoughts
The most important rule is not to fertilize your Japanese Maple more than you have to. Acer palmatum can often grow into a healthy and stunning tree with little to no fertilizer at all. Still, a modest amount of added nutrition can give it a little extra vigor. Nourish your Japanese Maple when necessary, but when in doubt, trust your tree to grow at its own pace.