There are numerous maple species for the garden or for keeping in tubs, which are mainly cultivated for their beautiful, red-colored foliage. The two best-known representatives are probably the red fan maple (Acer palmatum), which comes in many different varieties, and the red maple (Acer rubrum), which comes from North America. While the Japanese maple usually delights with red foliage all summer long, the red maple only shows its blaze of color in autumn. However, both can start to turn green for different reasons.
Green leaves on the red maple can be quite normal
Greening is normal for many Japanese maples
First of all: With many varieties of the red Japanese maple, it is completely normal for the tree to only show red leaves when they bud and in autumn. In summer, the leaves are naturally green. These varieties include i.a. such popular variants as 'Kotohime' or 'Deshojo'. Only a few red Japanese maples show an intense red color throughout the growing season. The rather little greening Japanese maples include u. 'Atropurpureum', 'Fireglow', 'Bloodgood' as well as various Dissectum varieties (which include the popular 'Garnet').
There are many possible causes for greening
On the other hand, greening can of course also have various causes, which are mostly to be found in an unsuitable location, in too much or too little sunlight and / or wrong fertilization. These lead to premature greening in the Japanese red maple and to the lack of autumn color in the Canadian red maple.
Unsuitable location
A lack of or insufficient sunlight is usually responsible for at least a weakly pronounced or even non-existent autumn color. Basically, the following rule applies to maples: the more the sun shines in the sky, the more intensely the color of the leaves turns. However, this is by no means a general rule, because many maple species prefer a semi-shady location and react to direct sunlight with a greening.
Incorrect soil pH
Another reason why the foliage turns green is the wrong pH value. Maples prefer a slightly acidic to neutral substrate and turn green as soon as it becomes alkaline. In such a case, it helps to improve the soil with acidic rhododendron soil.
Strong nitrogen fertilizer
Last but not least, too intensive fertilization - especially with nitrogen - leads to fading of the foliage. Maples, no matter what kind and variety, should only be supplied very moderately and preferably with organic fertilizers.
tips
Unfortunately, greening can also occur naturally in older specimens - younger, red-leaved maples are often more intense in color and sometimes lose it over the years.