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Friday - November 08, 2013

From: San Francisco, CA
Region: California
Topic: Propagation, Trees
Title: Propagating Quercus agrifolia (Coast Live Oak)
Answered by: Anne Van Nest

QUESTION:

I am a gardener for the city of San Francisco. I am just curious about the best way to prepare an acorn from Quercus agrifolia for planting. I have heard many ideas about using sandpaper and microwaving it in a cup of water or even placing the acorn in a fireplace and making a fire but I would really like to know if there is a more foolproof way to start it.

ANSWER:

Quercus agrifolia is the Coast Live Oak, a large, broad evergreen oak native to the foothills and coast of California. Propagating this tree does not need to be an extensive process. It seems that collecting the acorns just after they are mature is key. Below are two ways that the tree can be propagated successfully.

The USDA in their Plant Guide prepared by Dieter Wilken and Julie Burgher of the Santa Barbara Botanic Garden in Santa Barbara California have information about propagating Quercus agrifolia from seed just by direct planting them in soil. Here’s some of what they write: Oak seeds do not store well and consequently seeds should be planted soon after maturity. Nuts are considered ripe when they separate freely from the acorn cap and fall from the tree. Care should be taken to collect local fruits, because they may be adapted to local environmental conditions. Viable nuts are green to brown and have unblemished walls. Nuts with discoloration or sticky exudates, and small holes caused by insect larvae, should be discarded.
Propagation of coast live oak is highly successful by direct seeding at the beginning of winter. Once a site is chosen, prepare holes that are 10 inches in diameter and 4 to 5 inches deep. One gram of a slow-release fertilizer should be placed in the bottom and covered by a small amount of soil. Place 6 to 10 acorns in each hole at a depth of 1 to 2 inches. Temporary enclosures should be used to minimize herbivory by rodents or birds. A simple enclosure can be constructed from a 1 quart plastic dairy container with the bottom removed and a metal screen attached. Near the end of the first season, seedlings should be thinned to 2 or 3 per hole and to 1 seedling by the second season. Supplemental watering may be necessary if a drought of 6 weeks or more occurs during the spring.
Container Planting: Seeds may be planted in one-gallon containers, using well-drained potting soil that includes slow-release fertilizer. Tapered plastic planting tubes, with a volume of 10 cubic inches, also may be used. Seeds should be planted 1 to 2 inches deep and the soil kept moist. Seedlings should be transplanted as soon as the first true leaves mature. Planting holes should be at least twice as wide and deep as the container. Seedlings may require watering every 2 to 3 weeks during the first season. Care should be taken to weed and mulch around young plants until they are 6 to 10 inches tall. Natural live oak regeneration from seeds tends to occur sporadically during winters with above average precipitation that falls evenly throughout the season. Seedlings are especially sensitive to trampling and too herbivory by rodents, deer, and cattle. Common insects include moth larvae and tent caterpillars. Mature trees are especially susceptible to oak crown and root rot fungi (e.g., Inonotus, Ganoderma, and Laetiporus) which decay wood in trunks and roots. Activities that disturb or compact soil around trees, including construction and livestock grazing need to be avoided or carefully managed within the near the zone of leaf canopy. Summer irrigation near oaks should also be avoided, especially in urban landscapes, because it promotes oak root and crown rot. When desirable, mature trees consumed by fires may be allowed to recover from stump sprouts if replanting on large tracts is uneconomical.

And the NativePlant Network has a protocol for propagation of Quercus agrifolia that they have put on their website using stratification. They write: Acorns are collected between September 1st and December 15th. Mature acorns are brown. Collect acorns as soon as base of acorn around the cup turns brown. Float fresh acorns overnight in fresh water. Remove floaters. Acorns are refrigerated and kept moist. Soak clean acorns overnight in fresh water. Drain and rinse in a 5% bleach solution for 1 minute. Rinse. Place seeds in a plastic freezer bag with an equal amount of dry perlite. Keep in refrigerator at 15C. Check for germination after 1 month. Sow germinants with 1/4 inch or longer radicles. Check weekly until all have sprouted. Plant acorns 0.5 times the diameter of seed to depth and are laid on media sideways. Do not cover with media. Germinating acorns are sown in 2"x10" containers (Deepot 40) containing standard potting mix of peat moss, fir bark, perlite, and sand. Keep media around acorns evenly moist. Do not let media dry out. Place containers in protective cages to protect from birds and rodents. The plumule and leaves do not emerge for 1 to 2 months. Fertilize with Nutricote NPK (13-13-13) 3 months after sowing.  If additional fertilization is needed, use a liquid fertilizer (Plantex NPK) 1:100 ratio through Dosmatic injector for 1 month or more.

 

 

From the Image Gallery


California live oak
Quercus agrifolia

California live oak
Quercus agrifolia

California live oak
Quercus agrifolia

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