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Acorn: Collection and Planting of Acorns
QUESTION:
I will be attempting to plant acorns in the hope that they will germinate and become full oak trees. Several acorns will be set aside for later planting. Do you know how we can be sure which acorns are still "good"?
ANSWER:
Acorns should be collected in the fall from specimen trees, i.e., very healthy, vigorously growing trees. Characteristics worth noting when choosing a seed source include desirability of leaf color and shape, drought tolerance, absence of galls, trunk form, vigor and an upright growth habit.
Ripe acorns can be picked before they fall; often it is wise to do so in order to escape weevils which attack those which fall to the ground. Acorns that are brown in color are physiologically mature; those which are yellowish are not ripe. As a rule of thumb, a mature acorn will snap cleanly from its cup without leaving a tissue residue.
Discard acorns that float in water along with those that show pin-sized weevil exit holes. In other words put the acorns in a bucket of water and discard the ones which float. The floating ones are usually hollow. Live oak seeds frequently contain weevil larvae that prevent germination. Larvae in sound acorns (sinkers) can be killed by immersion in 120 degree F. water for 30 minutes. Higher temperatures will kill the seed. If they all have holes, save yourself trouble and just throw them away.
Ideally, acorns should be planted immediately after collection. Any remaining cups should be removed. Simply place the seed in a container with a well-drained potting soil. Water the containers when the potting mix begins to lose moisture. The seeds should come up in 3 to 4 weeks.
Acorn viability is adversely affected by dry storage. If acorns lose as little as 15 percent of their initial moisture, percent germination may be reduced by one-third; 20% moisture loss may reduce viability by 96%. This is why acorns that have been lying on the ground for 2 days may not germinate. If stored in damp peat moss, acorns will germinate and may remain healthy for a short period of time. After 4 or more weeks storage in wet peat they will begin to rot. Storage in dry sealed containers at 32 to 36 degrees F is the best alternative to immediate planting.
Acorns may be sown in flats in the greenhouse, sown outside in rows or in containers. A well-drained growing medium should be used in flats or containers. Acorns should be planted 1 to 2 inches deep. Organic mulch applied to the seedbed will conserve moisture, protect against soil crusting and cold temperatures and help control weeds.
The bottom line is that you need to plant fresh seed which sink when placed in a bucket of water. Also make sure the sinkers do not have weevil holes. Place the seeds in a well-drained potting soil.
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