Applying the right amount of Japanese maple fertilizer at the right time is a lesson in attentiveness and restraint. Exercise both of these when offering your Japanese maples supplemental nutrition and you’ll be rewarded with consistent, healthy growth. This article discusses how and when to feed Japanese maple trees and what products are the best ones to use.
In general, the Japanese maple (Acer palmatum) is prized for its vibrantly colored leaves and relatively compact habit. Japanese maple trees look lovely when planted amongst other ornamentals, along the edges of lawns, or as centerpieces in container gardens. They are easy to care for and prune (you’ll find pruning tips for Japanese maples here). Ultimately, the way you grow yours and your specific growing conditions should influence your decisions about whether and when to use liquid fertilizers, fertilizer pellets, or nothing at all.
How do you know a Japanese maple needs to be fertilized?
Truly understanding the needs of these beautiful trees starts with a good soil test. To learn all you can about the makeup and fertility of your planting bed, contact your local extension office about soil testing or use a quality DIY soil test kit. Then, let the results help to guide you.
Japanese maple trees prefer soil that’s light, well-draining, and rich in organic matter. And, since Japanese maples are acid-loving plants, the soil they’re in also should be slightly acidic. If your trees are planted in heavy clay or soil with a very basic pH level, they aren’t likely to thrive. What’s more, because pH problems can impede nutrient uptake, adding fertilizer in this instance won’t help. Instead, you’ll need to amend the soil with a mixture of well-rotted compost, worm castings, or other organic materials. Doing so will help to improve drainage and aeration, boost the numbers of beneficial microorganisms, and correct pH levels. Each of these fixes, in turn, naturally help Japanese maples to tap into the nutrients already present in your soil.
Now, let’s say the structure and pH of your soil are adequate but your soil test reveals that it’s low in nitrogen, phosphorus, potassium, or other essential micronutrients. If that’s the case—and as long as your Japanese maple isn’t a newly planted specimen—then you might want to consider applying a slow-release fertilizer designed for low pH feeders.
The best time to apply Japanese maple fertilizer
If you determine that the Japanese maples in your landscape do need extra nutrients, the best time to apply the Japanese maple fertilizer of your choice is in early spring a little before your trees begin to leaf out. By feeding your trees at this time, you help spur and support their early season growth. And, although you could, alternatively, apply fertilizer a little later in the growing season, you’d better examine the fertilizer package label closely first to see how long the application is intended to last. (If, for instance, you were to apply a long-lasting product in late summer or early fall, you could stimulate new growth at a time when your trees, instead, should be preparing for dormancy. With potential cold snaps just around the corner, those recently fertilized trees are now more susceptible to potential damage and stunting.)
The ideal NPK ratio for a Japanese maple fertilizer
You may recall that a fertilizer’s NPK ratio refers to the respective percentages of nitrogen (N), phosphorus (P), and potassium (K) contained by weight. As you choose the best fertilizer for your Japanese maples, you’ll want to look for this ratio, which is usually represented by three numbers separated by hyphens.
Requiring little nitrogen, phosphorus, or potassium, Japanese maples are fairly light feeders. (As such, applying that leftover lawn fertilizer with an NPK of 32-0-4 would be disastrous!) Fortunately, there are a few Japanese maple fertilizer products, such as Fox Farm Happy Frog Japanese Maple Fertilizer, which have been developed to serve the needs of Japanese maples. Listed with the Organic Materials Review Institute (OMRI), the Fox Farm product is an organic fertilizer with a much lower—and more appropriate—NPK ratio of 4-3-4. (Incidentally, that fertilizer is also appropriate for evergreens, hydrangeas, junipers, and dogwoods, among other ornamentals.)
Of course, there are plenty of other suitable fertilizers that don’t necessary scream “Japanese maple” on their labels. One such is Espoma Organic Holly-tone, developed for acid-loving evergreens and azaleas. With that in mind, you might already have an old standby in your garden shed that would work perfectly well. As a general rule, look for a fertilizer with a relatively balanced NPK ratio and a nitrogen content below 15 percent by weight.
Types of fertilizers for Japanese maples
You have some important choices to make when considering which Japanese maple fertilizer will best suit your needs. Should you opt for a fast-acting or slow-release fertilizer? (Check the next sections for details on these.) What about synthetic sources of nutrients versus organic? As you investigate different options, you’ll find some organic products are made up of a unique blend of fertilizers and specialty additives like Mycorrhizal fungi which can improve root efficiency and nutrient uptake for your Japanese maples and improve the long-term health of your soil, too.
Granular organic options
Granular fertilizers are designed to be slow-released over a long period of time. Often, these look like tiny balls or pellets which are worked into your soil’s top layers. When you water your trees or when it rains, the fertilizer grains break down and their nutrients become available to feeder roots within your Japanese maple trees’ shallow root zone. To help further slow nutrient release, some fertilizer pellet products may include polymer-coated synthetics. One such is TreeHelp Premium Fertilizer for Japanese Maple, which has an NPK of 10-20-22 and isn’t an organic product.
Unlike their granular counterparts, liquid fertilizers like this one are much more fast-acting. These may be helpful if you’re trying to get a newly planted tree established or if you wish to foliar feed your tree. As liquid fertilizers are typically sold in concentrate, it’s important to follow the label’s mixing instructions closely, and, when in doubt, err on the side of a weaker nutrient solution. That way, you’ll be less likely to burn your trees with too much fertilizer.
How much fertilizer to use on a Japanese maple
Determining how much fertilizer to apply is as important as choosing the right Japanese maple fertilizer. After all, if you use too much—or if you fail to water regularly—these products can cause fertilizer burn. You can also end up with rushed, leggy growth that’s more susceptible to storm damage.
Generally, older, more well-established Japanese maples can handle more fertilizer than smaller, younger trees can. Follow label instructions to determine how much to apply based on the size and maturity of the tree. And, if your Japanese maple is growing in a pot—and especially if you recently acquired it—you should ask about the tree’s fertilization history before applying extra fertilizer yourself.
How to apply fertilizer to Japanese maple trees
As mentioned, you should follow the instructions on your specific fertilizer packaging; however, here are some of the most common application methods for granulated and liquid fertilizers respectively:
- Typically, dry granules are worked into holes dug into the top four to six inches of soil. Depending on the size of your tree, you might sprinkle one-eighth to one-quarter cup of pellets in each hole and the holes themselves should be spaced every two to three feet apart within and slightly beyond the tree canopy drip line. After application, water the area thoroughly.
- Before applying liquid fertilizer, water the application area well. Dilute the liquid concentrate per the package instructions. (You might even use a slightly weaker solution than is recommended for your initial application.) Water nutrients in from just outside the trunk to the areas within and beyond the tree canopy drip line.
Care after fertilization
After applying your Japanese maple fertilizer, be sure to water well as this helps make nutrients available to your tree’s shallow root system.
Adding a layer of mulch over the entire root area (beneath the tree canopy) will also help to lock in moisture, facilitate water absorption, and nutrient uptake.
The Right Tree-tment
Knowing how and when to apply Japanese maple fertilizer appropriately comes down to paying attention to detail and using a light touch. Japanese maples don’t have a big appetite for nutrients, but if you think your tree’s growth could be a bit more robust—and if soil testing reveals deficiencies—then you might add a small amount of granular, organic fertilizer for long-term feeding or a small amount of liquid feed for a quick boost.
Choose a product that’s no more than 15 percent nitrogen by weight, since Japanese maples are particularly sensitive to excess nitrogen. Finally, it’s best to apply your fertilizer in early spring just before your trees begin to unfurl their new leaves (but after any frost danger has passed.)
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