Central Valley

Acorn to seedling to -- wait, where are the saplings?

You'd never know that California's native oak trees are at risk by the army of young seedlings sprouting in lawns and gardens this spring.

After a banner acorn crop last fall -- known to tree experts as a "mast year" -- young valley oaks, blue oaks and live oaks are popping up in some parts.

"It's ridiculous; we were just inundated with them this year," said homeowner Steve Barber, who lives in Granite Bay east of Sacramento. "I've probably got six to eight mature oak trees in my back yard and a couple of hundred little babies."

Arborist Ken Menzer said the origins of the ample acorn crop date to 2006.

"That spring was really wet, and because of that, in the fall the trees put out lots of buds for flowers," Menzer said. "Then, in 2007, we had a really dry spring, which is perfect for pollination. So in the fall of 2007 we had lots of acorns that were viable."

Tom Galloway owns Modesto's T&G Tree Service and has been working with valley trees for 30 years.

"I have never seen so many acorns," said Galloway, standing near properties and trees he tends south of the Tuolumne River. With every step, dozens of acorns crunch underfoot.

He hasn't spotted any seedlings, though, in these parts.

Bill Dufresne, Modesto's chief forester, said ground squirrels make it next to impossible for seedlings in riparian habitats. The squirrels harvest all of the acorns for their winter food supply.

Inside Modesto city limits, Dufresne said, the ash is the most common tree. But, "along the rivers and wild areas, the oak is still king."

For how long is anyone's guess.

The oak seedlings' tender, leafy sprouts face daunting odds against survival. Most will never grow up to become the giant gnarled oak trees that provide California's iconic foothill and valley landscapes, as well as valuable habitat for a host of birds and mammals.

Doug McCreary, natural re- sources specialist with the University of California Co- operative Extension, talked about a generation gap in the valley and foothill forests.

"In oaks, we find lots of seedlings, hardly any saplings and lots of mature trees," he said. "It just doesn't follow what you'd normally think."

Victims of mowing, whacking

When the 49ers arrived at the foot of the Altamont for the Gold Rush, there were so many oaks that the saying went abroad, "You could walk all the way to gold fields in the shade."

Much of that terrain once covered with oak woodlands now is covered with suburban houses, with some leftover oaks mixed in.

That means seedlings grow where they aren't wanted -- in lawns, in gardens, maybe right next to the house. These fall victim to the lawn mower and the weed whacker.

Even in protected oak preserves, the overwhelming major- ity never reach the sapling stage.

McCreary said there are several reasons for this, none of which has been isolated as the main cause.

Non-native grasses introduced for grazing cattle during the Gold Rush compete for water.Cattle, deer and sheep eat the young seedlings.

"The limitation does not seem to be the number of acorns, or the number of plants getting to be seedlings a couple of inches tall," McCreary said. "The bottleneck seems to be going from seedlings to saplings, or teenage size."

At the Deer Creek Hills Preserve in eastern Sacramento County, blue oaks, valley oaks and live oaks dot the green hillsides. The big trees likely are 200 to 300 years old, said Aimee Rutledge, executive director of the Sacramento Valley Conservancy, which runs the preserve. Around these mature trees, thousands of seedlings are pushing their way through the green grass.

But a recent study by a graduate student from California State University, Sacramento, found few trees younger than 65 years old, Rutledge said.

Clues at the riverside

Walking around Deer Creek Hills, one is hard-pressed to spot any young trees at all. It's hard to say exactly why.

"Oak trees have a long life span, and it's hard for us, who have a short life span, to relate to how they reproduce," Rutledge said.

There is one spot on the preserve that provides some clues, however.

Along a stretch of Crevis Creek, valley and blue oak saplings of various ages are thriving alongside a huge valley oak that recently collapsed and lies dying on the ground.

Rutledge said these saplings enjoy a combination of sunlight and water from the creek that those under large trees or far away from a stream lack. These conditions may hold the key to their success.

McCreary is part of a group trying to figure out why young oaks don't grow up to be adults. The research is being conducted at five sites around the state, including the Sierra Foothill Research and Extension Center in Yuba County. Young seedlings there are being protected in an effort to see what works best.

As for all those tiny trees sprouting in your lawn, it's too late to save them if you don't want to let them grow in place. Oak trees grow long taproots right away, making them hard to move.

"Right now, I hate to tell you, just mow them over," said Ray Tretheway, executive director of the Sacramento Tree Foundation.

"When an oak seedling sprouts up, and the first two leaves come out, that taproot is already two feet into the ground," he said. "You can't dig them up and transplant them at all."