Coast Live Oak Bonsai

Coast live oak is a moderate water mobility tree, meaning it needs to dry out between waterings—contrary to most broadleaf trees. Due to the thicker, rigid leaf and reduced transpiration, oxygen must be allowed back into the system before being thoroughly hydrated again.

Because coast live oak grows in the Mediterranean climate in California, it loves heat and can grow in incredibly hot, dry conditions. 

When kept in a deeper container that has a reservoir of water, full sun exposure will create tight inner nodes, small leaves, and a strong tree that is very responsive to bonsai operations.

Coast live oak bonsai is capable of tolerating heat in excess of 100 °F as long as it lives in a deeper container that can facilitate the root system. 

Coast live oak does not tolerate freezing temperatures when in a bonsai container. The smaller the container, the more susceptible it is, but the general rule is to not let your coast live oak bonsai freeze.

In a native region, you may experience a light frost, but never significant freezing. You should still protect your tree from temperatures when possible.

When fertilizing coast live oak bonsai, avoid high nitrogen fertilizers. Opt instead for a solid fertilizer once per month or a liquid fertilizer once per week during the growing season.

The best time for structural pruning and branching of coast live oak bonsai is in the spring, prior to growth. You can come back to pruning in midsummer after the tree has had time to produce a strong flush of growth and has built up a lot of energy.

Coast live oak can produce a second flush of growth toward the end of July to mid-August, but you want to avoid any heavy reduction of foliar mass or branching as you get closer to fall.

Without the foliar mass or the leaf to create the resources it needs, the tree cannot grow strong for the following year.

Refinement pruning and partial defoliation require you to prune back the elongated shoots to two active present buds and reduce the remaining leaf surface by two-thirds. This will stimulate ramification.

Coast live oak bonsai can have a variety of soil circumstances when repotting, depending on how much control you have over your watering.

You may use a solid akadama soil or a 3-1-1 akadama, pumice, and lava mix as long as you can customize your watering schedule. 

But if you’re using an automatic irrigation system, a 1-1-1 akadama, pumice, and lava mix is the driest mix you would want to use. For an increased capacity to produce finer ramification, you can use a 2-1-1 mix to provide the tree with more resources.

When repotting coast live oak, you never want to bare root or heavily reduce the sheen at any one time. The focus should remain on ensuring the health of the soil and the sheen. Sheen base trees thrive in deeper containers.

Three ways to propagate your coast live oak bonsai are through: 

 ● Air layering

 ● Cuttings; and

 ● Acorns

However, acorns tend to produce many genetic variations and can mutate considerably, making it impossible to predict the outcome.

Coast live oak bonsai suffer from a variety of pathogens, however, the main concern with this tree is sudden oak death—phytophthora ramorum—a root-borne pathogen that can be very challenging.

Cynipid gall wasps are a common but not overly damaging pest known to live on coastal live oak trees. The main damage caused by the wasps is leaf scorching.

The wasps die naturally from parasites, fungi, competing insects, and predators that live within the galls.

Spider mites can also be found on the bottom side of the leaf and can usually be removed with a good blast of water.