Our City Forest - California Native Plants

The native plants and trees in our ecosystems are indispensable. Native plant species are superior in supporting pollinators and local wildlife, such as bees, butterflies, amphibians, reptiles, and mammals, as demonstrated by ecologists, wildlife biologists, and entomologists. On the other hand, invasive plant species have the power to disrupt environments, diminish biodiversity, drive native species to extinction, and clash with them for scarce resources. This invasive species takeover can and is occurring everywhere, including California. For Californians looking to add some greenery to their yards, it  can be especially challenging to tell native plants from invasive ones. Fortunately, the general public can plant and obtain a wide variety of native California trees from Our City Forest in San Jose, CA. They take tremendous pride in the quality of their plants and go to considerable lengths to ensure that they all mature into robust, healthy trees. These are a few from their wide variety available at their nursery as of November 2023:

1. The Acer Macrophyllum (Big Leaf Maple) is a huge deciduous tree. Although it’s typically 50 to 65 feet tall, it can grow to a height of even 100. The diameter of the trunk on the other hand, can grow to over 3 feet. Its native range extends from southernmost Alaska to southern California in western North America, primarily along the Pacific coast. 

2. The Aesculus Californica (California Buckeye) is either seen as a tiny tree or a big shrub. It usually spreads out and has several trunks, with a broad and tall crown. This species, belonging to the Sapindaceae family, is the sole native buckeye in California. Early spring usually sees it leaf out and its creamy-white to pale pink flower spikes begin appearing- butterflies adore the blooms!

3. The Cercis Occidentalis (Western Redbud) is a little deciduous tree that grows in California's highlands and foothills. Early in the season, the glossy heart-shaped leaves on the slender brown branches are light green, but as the season progresses, they turn a darker shade. Bright pink or magenta, beautiful flowers appear in clusters throughout the shrub in the spring and give the plant a vibrant, eye-catching appearance in the landscape.

4. The Myrica Californica (Pacific Wax Myrtle) is a naturally occurring shrub of to the Myrtle family that is mainly found in northern and central California along the coast. It can also be found as far north as British Columbia and as far south as Los Angeles County. It has a lengthy lifespan and grows rather quickly. It develops actively in the spring and summer, reaching a tall shape up to 33 feet in height. Early summer is where you can bear witness to the blooming of its yellow flowers.

5. The Quercus Agrifolia (Coast Live Oak) is a recognizable, magnificent tree that supports the local flora and animals. Its massive canopy and twisted branches make it easy to identify. A diverse range of birds and butterflies are drawn to the acorns of the Coast Live Oak, which blooms in the spring and provides food and habitat for over 270 different kinds of birds and insects. These hardy trees can reach mature heights of 30 to 80 feet. They can also live for decades, frequently exceeding 250 years.

6. The Quercus Douglasii (Blue Oak) is a deciduous tree that can withstand droughts and gives local wildlife food and shelter. It provides food for insects, squirrels, and birds and serves as a host plant for numerous moth and butterfly species. Additionally, the blue-green foliage of this tree is what gave rise to its name. Blue oaks can reach heights of more than 80 feet, and their canopy can enlarge to at least 30 feet in width. 

7. The Quercus Lobata (Valley Oak) is the biggest oak species in North America. They can grow up to 60 feet in 20 years, 20 feet in 5 years, 40 feet in 10 years, and so on; fully grown specimens can live up to 600 years. Its wavy bark, which has a pewter tint, contributes to this species' appealing appearance. October is when acorns fall throughout most of the range. They are consumed by a wide range of mammals and birds, such as the California Ground Squirrel, Acorn Woodpecker, Western Scrub Jay, and Yellow-billed Magpie. Like many oaks, this tree is resistant to wildfires.

These are just a few of the many, many plants available at Our City Forest. To learn more on the different species/plants available at the nursery, you can visit their website ourcityforest.org or visit them in-person at 1000 Spring St, San Jose, CA 95110. Do your part in promoting biodiversity today by considering planting some native trees. Thank you :)

Sources: ourcityforest.org & calscape.org

Identifying Tree Pests and Disease

There are a lot of reasons that could lead to the decline or death of a tree. From insects to disease and fungi to lawn mowers and everything in between, the trees of our urban forest are constantly at threat. Identification and diagnosis of the decline of trees can be crucial in warding off a mass urban forest devastation, those of the like seen with Emerald Ash Borer, Gypsy Moth, and Dutch Elm Disease.  

There are two types of indicators that can lead you to knowing that a tree is under stress. Symptoms are effects that the causal agent has on a tree, whereas signs are what is left behind by the causal agent. An example of a symptom would be wilting of the leaves due to lack of water. An example of a sign is a fruiting body of a fungi of insect burrow holes. 

Some common signs and symptoms include:

• Leaf Spot- Spots of dead tissue on foliage: size, shape, color depends on causal agent

• Leaf Blotch- Dead areas on leaves on foliage: larger than leaf spots.

• Scorch- Browning and death of areas along leaf margins & between veins.

• Canker- Localized dead stem tissue.

• Stunting - Abnormally small plant growth.

• Gummosis - Exudation of sap or gum from wounds.

• Rust- Orange/reddish brown pustules on leaves.

• Gall- Swollen plant tissue.

• Chlorosis- Yellowing of green leaves due to lack of chlorophyll.

• Necrosis- Death of tissue.

• Die Back- Dead portions of the tree. (commonly seen on tips)

• Powdery Mildew- White or greyish fungal growth on the surface of the leaves

• Vascular Discoloration- Darkening of wood vascular elements, often along growth rings.

• Witch's broom- Abnormal development of multiple shoots.

Noticing these things can help save a tree from death or prolonged injury. If you see any of these signs or symptoms on a tree, you can do some research and try to identify the causal agent yourself. You can also reach out to an arborist and see if they would be able to identify the causal agent, and provide a recommendation as to how to pursue the tree. 

Biotic factors such as insects, disease and fungi are considered infectious, whereas abiotic factors such as moisture and temperature extremes, mineral deficiency, pollution, climate change etc are not considered infectious. Fungi and insects make up the largest portions of biotic factors. Insects are classified into three categories when it comes to effecting trees. Chewing insects that use their mouthparts to eat portions of the tree, usually the leafs (i.e Japanese beetles, gypsy moths and tent caterpillars). Sucking insects that use their straw like mouth parts to suck sugars out of portions of the tree, usually stems and leaves (i.e. aphids and scales). Lastly boring insects, who bore into the tree and either eat portions of the inner bark or create nests there; these insects cause the most damage to trees (i.e. Emerald Ash Borer, and bark beetles). 

Some Insects in the Bay area Include:

• Aphids - Small sucking insects that attach to stems and suck out juices and excrete a sticky chemical called frass. More info. 

• California Oakworm - Caterpillars that skeletonize oak trees, predominantly coast live oaks. More info. 

• Lace bugs - black shiny insects much like aphids, remove nutrients from leaves that cause white splotching. More info.  

• Tussock Moth - caterpillars with large appetites can defoliate trees quickly. Affects all species. More info. 

Western Tussock Moth Eggs Source:
(https://www.sacnaturecenter.net/visit-us/nature-blog/news.html?NewsID=60340)

Western Tussock Moth Larvae Source:
(https://www.thedailygarden.us/garden-word-of-the-day/western-tussock-moth)

When it comes to disease, fungi and viruses there are three very important factors to think about, the host, the pathogen, and the environment that make up the disease triangle. The host is identified as the plant that is in question; the pathogen would be the disease, fungi or virus; and the environment would be all the factors that affect both pathogen and host. 

Most trees are susceptible to at least one disease causing fungi, yet most fungi are actually good. Only a small portion of fungi are harmful to trees and other plants. Diseases can be carried by vectors, most commonly insects, this is seen in dutch elm disease where the bark beetle works as a vector. A common bay area disease, fireblight can be spread by bees (this doesn't make bees bad though).

Here are some common bay area diseases:

• Chinese Elm Anthracnose - Dye back on tips, black spots on leaves and cankers form at the base of the tree. More info. 

• Fireblight - very contagious bacteria disease, causes a burned look on stems, leaves and branches. Mostly affects pears and apples. More info.

• Powdery Mildew - White fungi that forms on leaves of plants. More info.

• Shot Hole Fungus - Causes holes and browning of leaves, as well as yellowing of stems. Affects Prunus species - including stone fruit and almond trees. More info.

• Sooty Mold - furry black mold on leaves, and yellowing of leaves. Common on fruit trees and attracts aphids. More info. 

• Sudden Oak Death - Caused by the water mold pathogen Phytophthora signs include cankers, twig by back and black/brown leaf spots. More info. 

• Sycamore Anthracnose - erratic branching, cankers, dieback, and defoliation. Fungal disease that affects most sycamores and maple trees. More info. 

Powdery Mildew Source:
(https://www.thespruce.com/powdery-mildew-1402500)

If you have any questions or concerns about a tree on your property you can reach out to a local arborist and see if they can provide some help. Sometimes solutions are simple, like a spray or soil injection. Other times they are extreme like with Oak Wilt where the tree has to be removed, chipped, chips hauled to a site where there are no oaks present and dumped, 4 ft trench created severing all roots, stump ground down two feet, and soil not wood chips placed on top, and the entire area painted with pruning sealing paint. This fungi is not present in California luckily.

I have compiled a set of extra readings and field guides for those more interested in the topic of insects and disease, specifically in California. Here is a good link to some of the most common harmful insects to trees in the United States for more reading. Also here is an identification key for California insects. Here is a field guide for diseases and insects for California oaks. Here is a more in depth training manual for insects and disease by the US Forest Service in California.

Tree Tapping and Maple Syrup

Ever really think about how maple syrup is made? It is many people’s favorite breakfast accoutrement, but most do not consider the story behind it. Well it comes from OCF’s oldest friend, the tree! Today on the blog we learn all about tree tapping and the process of creating maple syrup.

For starters, what trees can be tapped to make maple syrup? Maple trees of course! The syrup actually comes from the sap contained in these trees. The trees definitely need to be healthy and free of damage or disease to collect their sap, but size is also an important detail to account for when it comes to tapping trees. The tree must be mature if it is to be tapped for its sap. The minimum diameter size required is 1 foot. If the maple tree has a diameter of roughly 12 to 20 inches, it can be tapped only once. If the diameter is between 21 and 27 inches it can be tapped twice. Once the tree’s diameter surpasses 27 inches, it can be tapped three times. 

There are actually four main types of maple trees used for syrup making. They are: sugar, black, red, and silver maples. The sugar maple is, naturally, the best for making maple syrup. This is because it has a high sugar content. Sugar maples are predominately found in Canada and the northeastern United States, but can also be found as far west as Minnesota and as far south as Tennessee. These trees do well in various soils, but dislike very wet or very dry conditions. The black maple is the second most favorable for syrup making, as it has the second highest sugar content in its sap. Its growth range is more limited however, found within Canada in southeastern Quebec as well as the USA amongst central Wisconsin and down south to Tennessee. Coming in third is the red maple, which has a lower sugar content – but still makes great quality syrup. A pro of this tree is that it grows almost anywhere. It can be found growing all the way down in Florida and as far west as Texas. Lastly, silver maples can also make syrup but are these least desirable for this process – simply due to their low sugar content. As they grow early on in spring their sap can evaporate before being tapped. These trees do however have a large growth range similar to red maples. 

Fun Fact: While not one of these four popularly used types, the bigleaf maple, acer macrophyllum - which is found here on the Pacific coast - can also be used to make delicious syrup!

Now that you’ve learned about different types of maples, let’s get down to the details. First off, when is a good time to tap trees for sap? The ideal timeframe is from the end of January through the end of February. It is peak season when temperatures drop below freezing at night, but stay above freezing during the day. Secondly, how exactly does one tap a tree? Believe it or not, a power drill is used to drill a small hole in the tree. The drill bit size must match the size of the spile, which is the spout like instrument put into the tree that acts as a funnel to collect the sap into a bucket. The hole is created at a upward angle to allow sap to flow down via gravity. The hole goes into the xylem layer of the tree. Then the spile is hammered in and the collection bucket is hung. Sap flows out during the day when temperatures are above freezing. On average, 6 – 10 gallons of sap are collected in a syrup season.

How does sap become syrup? Initially, the sap is filtered through both a coarse and fine filter to remove debris. Then, it gets boiled. This is done at a temperature range of 212°F-218°F. This boiling will kill any bacteria present in the sap. As it is boiled, much of the sap evaporates. The sugars are then condensed and the texture begins to thicken. This liquid is then transferred to a stove top to complete its last step in its transformation to what we all know as “syrup”. This finished product is a ratio of about 67% sugar and 33% water. It is then filtered a final time and bottled while still hot. Bottling it while hot allows it to seal better and be stored at room temperate. Syrup that is bottled while cooled must always remain in the fridge or freezer. 

Fun fact: What many people do not realize is that it takes approximately 40 gallons of sap to make 1 gallon of syrup. How crazy is that!