The Oak tree is one of the most majestic of bonsai, with its thick, defined trunk and grand foliage. What’s more, they aren’t hard to find and are awesomely adaptable!
Regardless of whether you’re getting ready for your very first oak bonsai or hoping to score some tips, you’ve come to the right place.
First things first. Oak trees are of the Quercus genera. They are famous as long-lived, hardy and resilient trees. That said, there are a wide variety of oak species and a good number are suitable bonsai candidates. The most common of which are White oaks. The Quercus rober (English oak), Quercus lobata (Valley oak) and the Quercus muhlenburgii (Chinquapin oak) are prime examples of white oaks. They are deciduous and have large, lobed leaves and rough barks. These species are some of the most successful choices for oak bonsai.
Start your bonsai right with fresh, quality acorns. Gather them just as some have already started falling on the ground. Make sure that the seeds do not have holes. Holes are an indication that worms are already making a meal of your acorn, and we can’t have that. Healthy acorns make healthy bonsai.
Bury half the seed on high-quality coarse soil made up of part pumice, part compost and part organic substance to insure proper drainage and foster healthy root maturation. Place ‘em in the nursery and don’t forget to water every day.
Prune and repot seedling when it’s 6” tall or more. Don’t be stingy when it comes to cutting the taproot. Less is more. Leave only the very top with a rich root development; this will promote better root growth and branching. No worries about the little tree, oaks can withstand tougher stress than having most of its tap root trimmed away. Yes, sir.
Repot in the same high-quality soil with the acorn up. Avoid sunlight for about 2 weeks to give the seedling proper recovery time. In addition, delay fertilizing for about 4 weeks. The acorn seed will be able to supply the nutrients necessary for healthy growth.
The optimum time for collection is between the months of January and April. Your choice of wild oak should be those that are approximately 6” to 2’ tall. The stress of root-clipping will exacerbate water loss through transpiration. This can be reduced by snipping most of the leafage off except for a few at the branch tips, in order to force the plant to bud out from its trunk.
Oaks don’t really have fancy soil requirements. As long as there is sufficient moisture retention and proper drainage, a basic bonsai soil mix of part peat and part grit is perfectly adequate. Oaks will flourish in a wide scope of soil pH levels too—3.5 and 7.2.
Regularly water the tree at least once a day, preferably in the mornings. Oaks are tolerant of excess water in the soil that should, in fact, stay moist; make sure it doesn’t freeze in winter, though. Proper water flow is essential to encourage healthy rooting.
Sunlight is a healthy oak bonsai’s friend. They can tolerate the sun better and for longer than most other bonsai. They require a healthy dose of direct morning light but also need to be protected from the harsh mid-day sun. In the afternoon, they can be kept in the shade or under filtered sunlight. Oaks can withstand extended shade too.
Since flowers are not sought in oak tree bonsai, there’s no reason to hold off on supplemental nitrogen to encourage heavy trunk development; especially if they are grown in areas where sunlight is weak. It’s best to give the plant a balanced solution for top- and root-development. Some bonsai oaks will produce adorable bonsai-sized acorn fruits.
Some fertilizer break down and form a crust in the soil surface that can inhibit water absorption. Avoid this by scraping the crust and adding fresh soil.
Oaks are inclined to develop long shoots in the beginning of spring—after emerging from dormancy. Shear the new buds and cut nearly all foliage but leave about 30% unpruned. Snip in favor of the new growth on top to maintain a balanced appearance and promote thinner top- and thicker bottom-growth.
Oaks are well suited to the formal upright style. Shaping or wiring should be performed before the branches are hardened, that’s why it’s most often conducted after pruning. Proceed with perfect care to avoid damages like wounds on the bark or breaking of branches. Although you can try your hand on a few basic steps, these sensitive procedures are generally best left to professionals.
Repotting can be done every two years or so during the tree’s dormancy state, usually in winter or spring. Major root trimmings and subsequent repottings should be arranged in spring as well, especially with deciduous white oaks like the English oak.
Oaks have a healthy appetite for sunlight. When deprived of the sun for too long, they tend to foliate abnormally large or suffer from dieback. Increased exposure to sunlight will alleviate this problem.
Unhealthy oaks are also susceptible to fungal infestations. Prevent the spread of fungus by spraying with a hydrogen peroxide and water solution. A quart of water with about a tablespoon of hydrogen peroxide will do the trick.
If leaves start turning brown, check air circulation or the soil’s water absorption. Lastly, watch out for insects and caterpillars that can gobble leaves up and leave the oak leafless before you know it.