Three species and numerous cultivars of blueberry plants (Vaccinium spp.) grow across U.S. Department of Agriculture plant hardiness zones 3 through 9, although individual cultivars or species offer narrower potential growing ranges. The highbush blueberry (Vaccinium corymbosum) grows in the midwest, northeast, and parts of Canada, and performs best in USDA zones 4 through 7, the lowbush blueberry (Vaccinium angustifolium) is cultivated primarily in the northwest, Maine and Canada, or USDA zones 3 to 6, and the more heat-tolerant rabbiteye blueberry (Vaccinium ashei) grows in the southern United States, thriving in USDA zones 7 through 9.
Mulches around blueberry plants contribute to plant growth by suppressing weeds, conserving soil moisture, regulating soil temperature and creating an informal but protective border around the bush. Oak leaves can serve well as a blueberry mulch. Shredded oak leaves break down relatively slowly, reducing upkeep needs. While shredded oak leaves are good, composted oak leaves are an even better mulch, although it will take several months to turn shredded oak leaves into compost.
Rake the oak leaves into strips piled a few inches high on the lawn if they are not already shredded. Remove any branches, twigs or other debris, and run them over with a lawn mower one or more times, until the oak leaves are as shredded as you want them to be. You can use an alternative method, such as a leaf vacuum-mulcher to shred the oak leaves, if you wish.
Remove any weeds or grass from the area around the base of the blueberries.
Spread the shredded oak leaves around the blueberry plants, covering an area that extends at least to the shrub's drip line, the imaginary line on the ground that reflects the edge of the blueberry's canopy or branch spread. Create a loose, fluffy layer about 3 inches thick.
Pull the shredded leaves back from the base of each blueberry plant to establish a mulch-free zone extending at least 6 to 12 inches out from the blueberry stem. Mulch left directly in contact with the plant can trap moisture against the bark, causing disease problems, and can harbor pests.
Fluff up the shredded oak leaves by hand occasionally, or use a garden rake or fork. This will help to keep the shredded oak leaves from becoming matted and forming a layer that will block the movement of water and air into the blueberry's root zone.
Add more shredded leaves or other organic mulch to the mulched area as needed to replace the oak leaves as they break down. Aim at maintaining a loose mulch layer that is about 3 inches thick. When you add new shredded leaves or other materials, lightly blend the new material with the old shredded leaves to avoid creating distinct layers of different materials within the mulch.