Gather acorns to grow oak trees

California’s American Indians were more than hunter gatherers. They used fire to burn away the dry chaff so acorns could fall on barren ground to make collecting easier. This also reduced the population of acorn weevil pupa underground that threatened this staple food.

Gathering is more than just scooping up the nuts because some may contain the acorn weevil’s progeny. This bug lays its eggs in a developing acorn while still on the tree. After the acorn falls, the eggs hatch into larvae that consume the contents of the acorn, then bore a hole to exit into the soil where they pupate. Gathering required inspection of every nut to spot this tiny hole. Just like the bad apple that spoils the barrel, one infected acorn can be the source of additional larvae to damage the winter food supply.

It is these perfect nuts that are the best way to grow native oak trees in your yard or for starting groves on larger rural properties. Those that fall from locally native oak species will be best adapted to your microclimate, and they will prove more resistant to regional pests and disease, too.

Growing oak trees from acorns is not only free, it is a great way to teach the kids how these important trees survive drought. Gather your acorns on an autumn family outing, as with an Easter egg hunt. Instruct the kids to seek only the largest, most perfect acorns. In the process you’ll see the acorn of each species is slightly different in size and shape.

Back home, simply place your nuts in a plastic bag and refrigerate for a month to simulate winter. Then remove them and place in an empty flowerpot outside, where they will be exposed to rainfall and sun. Check your acorns every week for longitudinal cracks that tell you the seed inside is beginning to grow and ready to plant. Unviable acorns will not crack, so you’ll know which ones to separate from the healthy seed.

Many of the seedlings begins life in a unique way. They germinate with an aggressive tap root that exits through the cracked shell and grows immediately downward at a rapid pace. This is particularly true of oaks in the arid states with a long dry season in summer and fall. That tap root can be 2 feet deep by the time midsummer arrives. It supports a single slender 6-inch stem that produces a few small leaves that first year. The ratio of root growth to minimal stem height tells us tap root formation is critical to survival.

This is why growing native oaks in pots doesn’t work well. When the tap roots root hits the bottom, it’s forced to bend and distorts. These never achieve their natural depth, thus reducing the natural drought resistance of the tree throughout its lifespan. But when grown from acorns sown directly into natural ground, the tap root is free to go deep and access moisture over the long dry season.

Plant your cracked acorns just an inch or so below the soil surface so they won’t be picked up by blue jays and other wildlife. Use a stick or marker to identify where the acorns are buried. All too often the little stem is lost in the lush spring grasses, then trampled, mowed or grazed to death. Protect them if necessary with a tube of hardware cloth or fine plastic netting if rabbits and deer are present.

In drought years, some oaks will produce a bumper crop of acorns to ensure survival of the species if the parent tree dies. Therefore this year might be the best time to gather and plant your own oak woodland. The rains will return, and when they do your acorns will be ready to root deep and thrive, surviving drought just as their ancestors did with the same deep tap roots that’s key to survival in the west.