Proper fertilization is one of the keys to successfully growing Japanese maples. Although Japanese Maples don't require high amount of fertilizing, maintaining a low level of fertility throughout the season is necessary to keep your trees healthy and happy.
Fertilizing Japanese Maples at the proper time is also important. Fertilizing at the wrong time can cause damage to your tree. Avoid this common mistake at all costs. See TIP 3
Should you use controlled release or liquid type fertilizer?
See my answers below to these common questions about fertilizing Japanese Maple Trees.
Tip 1 Maintaining a constant low level of fertility will keep your trees healthy throughout the year. Applying high levels of nitrogen is not recommended. Avoid using high N lawn fertilizer on Japanese Maples. Japanese maples look best and develop thicker stems when allowed to grow at a slower speed. Applying high amounts of nitrogen will cause excessively fast growth which will weaken the plant. Weak branches can lead to damage if you are located where icing during winter is a problem.
Tip 2 Fertilizing your Japanese maple with the proper type of fertilizer should be done either late winter while the ground is still cold, or after the last freeze in the spring. I recommend using a slow or controlled release type fertilizer. Commercially known as Polyon or Osmocote these are the most common and both work very well on Japanese maples. We use both successfully in our Japanese Maple production.
When using a slow release type fertilizer pellet type it is best to bore a hole about 6 inches deep into the soil about half way between the main trunk and the drip line of the branches. IMPORTANT: Scattering slow release on the top of the soil does not allow the fertilizer to maintain a constant moisture level inside the pellet, resulting in sporadic and possibly untimely releases. Bore several holes around the tree and divide the proper amount of fertilizer recommend by the manufacturer by the number of holes. Drop the fertilizer into the hole and fill the remainder of the hole with soil. Water around the tree and now the tree is fed for an entire year. As the tree grows the amount of fertilizer will need to be increased. Tree fertilizer spikes also work well and are easy to use. Follow recommended rates based on the tree size.
Tip 3 I only recommend using liquid type fertilizer like Miracle Grow on Japanese maples during the first summer, and only to help establish the tree. Once you see good growth you can stop liquid feeding. IMPORTANT; Do not liquid feed in late fall or early spring. Liquid fertilizers encourage Japanese Maples to grow instantly, this is not recommended as early freezes in fall and late freezes in spring will cause damage or kill your tree.