Oak leaves as mulch for fruit trees
Is it ok to put oak leaves as a mulch under fruit trees? Thanks, Margot Vance-Borland
Benton County Oregon
The main concern people often have with using oak leaves is that they will acidify the soil. From a previous response to this question: "It is often assumed that … acidic mulches will lower soil pH. However, in all but the sandiest soils, soil pH is strongly buffered (resists change), so soil pH changes very little after applying most mulches. Some changes in soil pH may occur in the top 2 inches of soil, especially if mulch is applied repeatedly. In general, though, mulches do not change pH enough to be a major concern for woody plants. Although oak leaves have an acid pH (4.5 to 4.7) when they are fresh, the breakdown products are neutral to slightly alkaline."
So oak leaves should be fine. When mulching under any tree, make sure not to pile the mulch against the trunk, as this can encourage damp and disease. Allow 6" mulch-free around the trunk flare. Also, oak leaves are fairly slow to break down and can pack down during the winter; if you shred them before placing them, they will break down faster and stay looser.