Plant Doctor Archive

Where are the acorns?

About 10 years ago, my husband planted pin oaks around his duck pond in the hope of getting acorns to attract ducks.  Recently he was told that they do not produce acorns until they are about 20 years old. Is it true? Can the acorn production be accelerated by judicious pruning?  Poor husband, who is 78 this year!

The pin oak (Quercus palustris) is a native of North America.  It is commonly grown for its pyramidal habit, green leaves which turn red in Autumn, and fast-growing nature. Trees can reach 35 metres in height and can live to at least 140 years of age. The name appears to come from either the "pin knots" found in the wood, or short pin-like stubs found on the lower trunk. Pin oaks do best in full sun and moist, acidic soil, but will tolerate partial shade and drier soils if given summer watering.  The acidic soil is very important, with neutral or alkaline soils leading to discolouration of the foliage.

It is true that pin oaks usually take 20 years to produce acorns, but some trees have been reported to fruit after 15 years in North America. Many Northern Hemisphere trees grow much faster in New Zealand than in their native range, so I would start getting hopeful in a few years that some of your husband's trees might give him some acorns for his ducks!

Pruning is a good idea to maintain the tree form and let light in, but is unlikely to quicken acorn production.

Advice by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor of Resource Management.

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