How To Fertilize And Water A Japanese Maple Tree

Japanese maples are considered as the most special focal points in landscapes where they will grow. Few plants equal the beauty and provide the graceful forms, textures and color throughout the seasons as Japanese maples. One Japanese maple can make a landscape. 

As you may know, Japanese maples aren't the lowest cost plants on the market, so you want to make sure to plant and care for them properly. Contrary to popular belief, when planted right and in the right spot, Japanese maples are surprisingly easy to grow and maintain. 

Here's a breakdown of what you need to know regarding feeding and watering Japanese maple trees...

Evaluate Soil Conditions 

Though not absolutely necessary to do, before fertilizing your Japanese maple, the best starting point is a soil test. Soil tests are done to determine soil pH and essential nutrient levels. Your local Extension Service might provide soil testing services or you can test soil yourself with a soil testing kit or soil pH testing probe.  

TIP:  Keep in mind that construction and many other factors often result in soils that differ from one landscape to the next, and even from one area or spot to another in a landscape. In other words, the soil in your front yard may be much different than the soil in your backyard. So, when growing such a magnificent, long-lived tree as Japanese maple, it's always a good idea to test the soil in the area you intend to plant one.

Soil pH is Important!

Soil pH is a measurement of the alkalinity or acidity of soil and is measured on a scale of 1-14, with 7 as the neutral mark. Any measurement below 7 indicates acid soil conditions, and anything above 7 indicates alkaline. 

Japanese maples prefer a moderately acid to neutral soil ranging from 6.0 to 7.0 on the pH scale.  Once you know the soil pH, if necessary, you can adjust the pH to meet the needs of your Japanese maple.

Testing Soil pH
If you're unsure about the pH of your soil, and whether or not it's suitable for growing Japanese maples, it's a good idea to test the soil pH in the planting area. You can quickly test soil pH with a inexpensive soil test kit or pH tester probe. 

To raise the pH (make more alkaline) you can add pelletized limestone to the soil. To lower the pH (make more acid) you can apply Soil Sulfur, Aluminum Sulfate, or Chelated Iron. Adding organic compost to the soil or using compost as mulch can also help to increase acidity and maintain acid soil conditions.

Feeding A Japanese Maple Tree

(Scroll down for watering tips)

Note:  Do not fertilizer a Japanese maple at planting time. Wait until the following spring after planting to begin feeding, and only if necessary.

When to fertilize a Japanese maple?

I fertilize my Japanese maples in spring, after new leaves have begun to emerge, but only if they were looking a little dingy during the previous growing season. If they were healthy looking, I usually skip it. That said, I always apply a 1 to 2" layer of cured, shredded or chipped wood mulch or pine straw around the tree in spring. As the mulch decomposes it will add vital nutrients to the soil that your Japanese maples will appreciate. Mulch will also help to conserve moisture and suppress weed growth throughout the growing season.

Note:  Avoid the use of freshly chipped wood for mulch until it has cured in a pile for at least 6 months, a year is better. Avoid placing or piling mulch directly against the base of your plant as this could cause the bark to rot. 

What type of fertilizer?

When feeding a Japanese maple, you can apply a slow-release shrub and tree fertilizer at half the recommended rate for other types of trees. That said, I usually go with and recommend a mild, organic plant food.  Avoid the use of 10-10-10 and other similar quick-release fertilizers that could burn the roots of your tree. 

As mentioned above, I always spread a 1 to 2 inch layer of cured, shredded wood mulch or pine straw around my Japanese maples every spring. As these organic mulches decompose they will add nutrients to the soil your Japanese maple will appreciate.

How much fertilizer? 

This will depend of course on the size of the tree you are fertilizing and the type of fertilizer. Regarding slow-release shrub and tree fertilizers, you'll find application instructions on the package. I would suggest applying half the recommended dosage for other types of trees. If you choose a mild organic plant food, as I highly recommend, you don't have to worry as much about burning the roots of your tree, even if you over-apply. 

Note:  Avoid the use of raw manures around your Japanese maple tree. 

Where to spread the fertilizer? 

The root system of a Japanese maple tree may extend several feet deep into the soil, but the majority of the feeder roots responsible for absorbing nutrients are in the top 12 inches of soil. Spreading fertilizer on the soil surface is sufficient to reach these feeder roots. Spread fertilizer evenly around each tree, beginning at least 1 foot from its trunk and to a point beyond the drip line (branch perimeter) of the canopy. For every 5 feet in height of your tree spread the fertilizer or compost 1 foot beyond the drip line. 

Note:  If the soil is compacted or subject to excessive water runoff, the fertilizer can be applied in a series of holes 6 to 8 inches deep in the same area with about five holes per 1 inch of trunk diameter.

Watering Japanese Maples

Young, recently planted Japanese maples require a moist but well-drained soil. Good soil drainage is critical and proper watering is especially crucial when young trees are working to establish a root system during the first two years after planting.

VERY IMPORTANT!!  As with so many other types of ornamental plants and trees, a constantly soggy or wet soil due to over irrigation or poor drainage in the planting area can cause the deadly root rot disease. Above-ground symptoms of root rot are browning or blackening of leaves. If this occurs, check soil moisture with your finger or a moisture meter and reduce watering or improve drainage in the area where your tree is growing. Recently planted trees, which have yet to grow new roots, can be lifted and replanted in a raised mound to ensure proper drainage. Wait to replant established trees until winter, when the tree is in dormancy and follow the instructions provided in our article How To Relocate And Transplant A Tree

Here's some watering tips:

Note: When watering with an automated irrigation system it's best to set your timer to water during the early morning hours and not in the evening or at night, which can lead to the onset of fungus and other foliage diseases. During the first few weeks after planting, check soil moisture often and adjust irrigation time if necessary to keep the root ball and surrounding soil moist, not wet or too dry. Also keep in mind that when watering with an automated irrigation system, which doesn't water deeply, that to water deeply enough to soak the root ball and surrounding soil to a sufficient depth you may need to provide supplemental water and deeper soakings by hand with a garden hose. 

Warm Season Watering

At planting time during spring or summer
Water deeply at planting time, making sure the root ball, and the surrounding soil, is moist all the way down to its base. Then, each day thereafter, check the soil moisture and only provide water if the top 2 inches of the soil has dried out. Eventually you'll get a general idea as to how often your tree might need water, but still always check soil moisture before watering.

During the first growing season
After planting a new Japanese maple in the ground, especially during the hotter summer months, the tendency is to think it has to be watered every day in order to grow. However, in average garden soil, you should not have to water your newly planted Japanese maple every day. More often than not, this causes soggy soil conditions that can lead deadly diseases such as root rot. In the absence of sufficient rainfall, water your Japanese maple only as needed to keep the root ball and surrounding soil damp to moist, not wet. Keep in mind that deep soaking less frequently is much better than splashing just a little water around the tree every day. Deep soaking promotes deep root growth and can reduce water loss by evaporation. 

Note:  If the leaves of your Japanese maple are browning around the edges or wilting, this can be the effect of either dry or over-saturated soil or from leach scorch after a long and hot summer. So, before watering, make sure to check soil moisture using the finger test or a moisture meter. If the soil is moist always hold off on watering.

Established Japanese maples won't require as much attention to checking soil moisture and watering. They have good drought tolerance and will rarely require when dormant during the winter months. That said, in the absence of rainfall, and especially during a warm season drought, even established Japanese maples may need supplemental irrigation. During a drought, wilting leaves are usually a sign that your tree could use a good deep soaking. To be on the safe side, always use the finger test or a moisture meter to check soil moisture before watering.

Cool Season Watering

Japanese maples won't require much if any supplemental water during the winter months, when they are dormant without leaves and not actively growing. Provide water only if necessary to keep the soil damp. Be extra careful not to overwater!

At planting time during fall and winter
At planting time you'll want to soak the root ball and surrounding soil in the planting area deeply after planting. Thereafter, check the soil moisture every few days until you've determined about how many days or weeks go by until the soil has dried somewhat and water is needed. With sufficient rainfall during the fall and winter months you may not need to water trees again until after new growth has emerged in spring.

Note:  If you have an automated irrigation system it's best to cut it off during the winter, only running it manually on occasion and only when and if necessary. Provide water during the winter only if there's been a prolonged period of dry weather.

Other Helpful Watering Tips
  • Water Japanese maples in the early morning. Watering in the late evening or at night can cause fungus and diseases to develop.

  • To avoid leaf scald, when watering a Japanese maple, avoid splashing water on the foliage, especially during the hotter parts of the day when the sun is shining. If you have an irrigation system, run it early in the morning, just before or after sunrise. 

  • During winter, if the weather has been dry and forecasters are calling for a deep freeze, deep soak the ground around your tree. Doing so helps to prevent freeze drying of roots.

  • Mulching around your trees can reduce the frequency of watering and suppress weed growth. Avoid placing mulch at a thickness of more than 2 inches. Also avoid piling mulch up around the base of the tree, which can cause bark to rot. Keep mulch a few inches away from the trunk. 

  • Control weeds as these will rob water and nutrients from your tree, not to mention steal the show!

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