In my recent articles about our Western Sycamore trees (Platanus racemosa), I've often lamented the absence of new saplings sprouting from fallen seeds, painting a somewhat bleak picture for the future of these iconic trees that make our park unique.

I am thrilled to report that this past year has proved me wrong! Immediately after the 2023 flood waters receded, the newly excavated creek banks seemed lifeless; however, hidden amongst the gravel and debris were the promises of life yet to come. 

Discovery of Baby Sycamores

On a breezy September morning, I went out for a quick walk along the edge of the creek to observe what was starting to grow, expecting to notice a mixture of the usual invasive species like palms, eucalyptus, and stinkwort. As I combed the shoreline, looking at all the little green sprouts poking up, I found myself pleasantly surprised to see quite a bit more diversity. There were tons of cottonwood and willow saplings, tule, watercress, Spotted lady's thumb (new to me!), and American nightshade, amongst many other species. 

And then, something else caught my eye: a small plant jutting out from the rocks with vaguely familiar leaves. I crouched down to inspect a bit closer.

Once the initial excitement subsided after finding this baby tree growing nonchalantly on the creek's bank, I glanced around at the nearby wildlife with a new perspective. I continued along the edge of the creek with a pep in my step, and within a few feet, I spotted another one. This one was a bit smaller, but it still had that same fuzzy texture, and three fingers pointed at the sky.

Another.

And another!

Since then, we have been going out with a GPS navigator and recording all the baby sycamores we can find. We have seen around 200 growing along the creek so far, with some big swaths of creek yet to be explored. 

Factors Contributing to Growth

I was flooded with intriguing questions once I could fully process this exciting discovery.

Why are they growing this year?

Why didn't they grow last year?

Will these young trees survive and grow into adult trees?

Have sycamores been happily sprouting in the park but not surviving their first years, only to die before being noticed?

How can we ensure that these do survive?!

I only know one thing for sure—I am not an expert! But I do have some ideas.

First of all, let's recall the great flood of 2023! Sycamores have a very specific ecological niche where they can thrive. Lower Sycamore Grove Park can be described as a Sycamore Alluvial Woodland. The key word here is "alluvial," referring to the ephemeral quality of the soil, constantly recharged with silt, clay, and gravel (alluvium) from upstream.

A good example of another alluvial system would be at the beach.

Each time the tide rises and falls, the beach itself changes. The currents carry sand away while new sands are being deposited. Driftwood drifts onshore and spends an afternoon up there until it is again carried away. Instead of constant waves pounding the beach, we have periodic flooding events that rearrange the stream channel, sending logs and gravel downstream and replacing it with organic material from upstream. Unlike the constantly changing beaches, these floods happen on average every ten or so years, which (hopefully!) gives the newly enriched soil time to send up some hardy enough trees to withstand the next flood. 

There is also the convergence of another significant factor that plays a role in this large-scale recruitment of baby sycamores.

The draught was declared to be over, allowing the Department of Water Resources to take advantage of the surplus of flowing water. The South Bay Aqueduct pulls water from the Bethany Reservoir, fed by the Delta, and carries that water via man-made canals over the Altamont Pass, along the northwest edge of Lake Del Valle, and off to Santa Clara, delivering water along the way. Because of this influx of excess water, our Arroyo Del Valle (and the Mocho Creek that flows through Livermore) has been continuously flowing all year, supplied by delta water via the aqueduct. The arroyo would have typically ceased flow by late summer, even after such a significant rainfall. 

The purpose of this unnatural flow is to 'recharge' the aquifers or groundwater for human water consumption, but raised groundwater levels can also be beneficial for any shallow-rooted plant. One of the biggest hurdles to overcome when planting container-grown sycamores into the park is supplying them with ample water for their first few years, at least until they can establish an effective deep root system. I assume that this easy access to water through what would have otherwise been a hot, dry summer greatly impacted the success of these saplings.  

Monitoring and Future Prospects

We are excited to continue to keep an eye on these young trees! As I wrote this article in December 2023, while walking along a stretch of creek to check on the progeny, I saw their tiny three-fingered leaves starting to take on the characteristics of yellow and orange leaves preparing to drop soon.

It's time for the sycamores to patiently wait out the winter months until the warmer weather wakes them up again. If we are lucky, these young trees will be taking this time to continue growing their root systems, and then in June or July, they will open their patient leaf buds, reaching up little fuzzy hands to soak up some delicious California sun again. 

Note from the Author 

We are still collecting cuttings and learning how to plant a new generation of trees in the park. Here are some successes from last winter's cuttings and a new batch from this year!