Q. Many oak trees sprout on my property. Can I transplant them, or is it better to plant acorns in order to grow oaks where I want them?
— Sid B., Los Osos
A. In general, you’ll be more successful if you plant an acorn where you would like a tree rather than trying to transplant oak seedlings. Seedlings quickly develop long tap roots (as you know if you’ve tried to pull them up). It’s difficult to move them without damaging roots.
Acorns from healthy local trees give the best results. We live in a region of microclimates, and oaks adapted to Paso Robles may not thrive in Los Osos. You can try planting non-local varieties, but be aware they may not thrive. If you’re aiming to start an oak woodland, you should certainly use local acorns.
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October into November is a good time to collect acorns for planting; they are ripe when they start turning from green to brown and detach easily from their caps. For best results, pick or shake them from trees rather than collecting them from the ground. Wash acorns in a bucket of water and discard those that float. Dry them and put them in plastic bags in the refrigerator for about a month. After first rains, dig out and replace several feet (if possible) of soil in the planting spot to give tap roots an easy start. Then plant acorns on their sides in damp soil, ½ to 1 inch deep. Seedlings may need some water, but taper off watering as they mature; summer watering can lead to several kinds of fungal disease.
Oaks can also be started in containers. Collect and refrigerate as described and plant acorns in pots. Tall, narrow pots will accommodate long taproots. Seedlings can grow in pots for up to a year before planting out. After planting, keep down competing weeds and use barriers to prevent pests from eating young trees. The University of California offers online tips for growing oak trees here: http://anrcatalog.ucdavis.edu/GrasslandsHardwoodRangelands/21538.aspx.