“These trees which he plants, and under whose shade he shall never sit, he loves them for themselves, and for the sake of his children and his children's children, who are to sit beneath the shadow of their spreading boughs.”

Author: Hyacinthe Loyson

I love to wander among trees, to see and hear the leaves swaying in the breeze, observe birds darting about the branches, squirrels running up and down the trunk, and insects flitting about. I have spent many contented hours sitting under a tree reading a good book. Trees mark the seasons of our lives, blooming in the spring before producing green leaves, producing fruits or nuts in the summer, changing colors in the fall, standing bare and stark during the winter months. I particularly love the Valley Oak tree (Quercus lobata) with its distinctive lobed leaves, the acorns it yields, the fascinating oak galls produced by tiny wasps, and their historical importance to the original people of California as a staple food source.

Arbor Day

Along with 50 countries around the world, the USA celebrates trees on Arbor Day. The day is celebrated during the spring tree planting season. In the USA, the date is typically the last Friday of April, which this year was Friday, April 26. The date varies around the world depending on geography, weather, and if in the Northern or Southern Hemisphere.

But why do we commemorate trees and how did Arbor Day get started?

Benefits of Trees

From the beginning, trees have provided us with the oxygen we breathe, along with food, shelter, medicine, and tools. To list a few of their other benefits:

• Trees help combat climate change – Trees absorb carbon dioxide (CO2), which is contributing to global warming. They remove the CO2 from the air and store the carbon. In one year, an acre of trees can absorb the same amount of CO2 produced when the average car is driven 26,000 miles.
• Trees clean the air – Trees absorb odors and pollutant gases such as nitrogen oxides, ammonia, sulfur dioxide and ozone and filter particulates out of the air by trapping them on their leaves and bark.
• Trees provide habitat for wildlife – Sycamores and oaks are among numerous trees that provide homes for many species of birds, mammals, insects, amphibians, and reptiles.
• Trees cool cities – Trees deflect the sunlight, cooling the air up to 10°F by shading our homes, buildings, and roads.
• Trees prevent soil erosion – Trees reduce water runoff by allowing the rainwater to flow down the trunk, onto the earth below. Their roots also slow runoff and hold the soil in place.
• Trees provide wood and paper – Trees help us build our homes and the paper we write on.
• Trees beautify urban spaces – Trees can mask unsightly concrete walls, parking lots, and unsightly views. They help muffle the sounds of the city and create eye-soothing canopies of green. They absorb dust and reduce glare.
• Trees provide personal and spiritual values – During our busy lives, trees can give us a piece of nature and moments of tranquility.

Arbor Day History

“Arbor” literally translates to “tree” from the Latin word arbor. The origins date back to the early 1870s to Nebraska City. Julius Sterling Morton and his wife, Caroline, planted a wide variety of trees on 160 acres of what was then a flat stretch of prairie. Through his job as editor of the state's first newspaper he spread his knowledge of trees, extolled their importance to the state of Nebraska by reforesting the empty plains. Morton proposed to the Nebraska Board of Agriculture that a day be designated to encourage people to plant trees. The first Arbor Day was held on April 10, 1872. The day was a huge success with approximately 1 million trees being planted.

The tradition quickly spread and within 20 years the day was celebrated in every state but Delaware. On April 15, 1907, President Theodore Roosevelt, a conservation supporter, issued an “Arbor Day Proclamation to the School Children of the United States.” In 1970, Arbor Day became nationally recognized due to efforts by President Richard Nixon.

People can celebrate Arbor Day by planting a tree (which can be dedicated to a loved one) and spending time caring for the trees we have. Morton's words resonate strongly today as climate change becomes a serious threat: “Other holidays repose on the past: Arbor Day proposes for the future.”

How Can We Help?

Some of the ways we can help preserve trees are:

• To reduce the demand for paper, check out books from your local Stanislaus County Library instead of purchasing new ones.
• Help protect existing forests – Encourage reduced cutting down of healthy forests by supporting sustainable reforestation.
• Afforestation – Support the planting of new forest plantations, which can enhance existing forest cover and help reduce global warming with carbon sequestration.
• Continue to water your tree, even during a drought. If you shut off lawn water, don't forget to deep water your tree! You can use a hose or soaker hose to water under the drip line.
• And, of course, plant a tree! You can volunteer for local organizations when they have tree planting days or plant a tree in your garden.

An excellent resource on care and selection of trees is Stanislaus County's Master Gardener “Trees in Your Home Garden,” https://ucanr.edu/sites/CEStanislausCo/files/341553.pdf

Additional resources include on how to plant a tree: https://ucanr.edu/sites/UrbanHort/files/80160.pdf, and on pruning trees: https://ucanr.edu/sites/UrbanHort/files/80116.pdf

Favorite Tree?

Do you have a favorite tree? Write in our comment section what your favorite tree is and why?!

Denise Godbout-Avant has been a UC Cooperative Extension Master Gardener in Stanislaus County since 2020.

This article was originally published on April 25, 2022.

Our last newsletter may have prompted you to have more questions about citrus. The good news is, the topic for January Classes at Stanislaus County Libraries is (you guessed it) Growing Citrus Trees! We hope to see you at one of these free classes.

You can also see a list of our classes on our calendar by visiting our website at https://ucanr.edu/sites/stancountymg/Calendar/

p.s. February's topic is Spring Vegetable Gardening, stay tuned for more information!

Our UC Master Gardener Help Line often receives calls about citrus. Here are five commonly asked questions about how to care for this juicy, delicious fruit tree.

1. Why are the leaves on my orange tree turning yellow?

It's common for citrus tree leaves to turn yellow in winter*. Fertilize to provide the tree with nutrients now, then watch as leaves green up in spring. Avoid fertilizing in fall, which encourages new growth favored by pest and can leave the tree susceptible to frost injury.

 

2. How do I know if my oranges are ripe/when should I pick my oranges?

Oranges are ripe when (drumroll please) the fruit tastes ripe! If you pick an orange and it tastes sour, wait, then repeat the following week until the fruit tastes sweet. Oranges picked unripe will not ripen, no matter how long you leave them on the counter.

You don't have to pick all your oranges once they ripen. In fact, the best place to store oranges is on the tree, where they stay fresh! Pick as needed, unless temperatures below 28 F are predicted, then you'll want to harvest.

 

3. What is this pest?

When clients bring samples of citrus branches in to our office, we often see pests like cottony cushion scale, soft scale, or whiteflies. In addition, ants, along with a dusty looking fungus called sooty mold, may be present.

Scales and whiteflies suck plant juices and weaken the plant. Ants do two things:

• Protect pests from predators like ladybugs, parasitic wasps (very tiny wasps) and lacewings.
• “Harvest” honeydew (a sticky sugary substance excreted by these pests) for food, in a symbiotic relationship that does not include the gardener.

You can find easy-to-read, UC IPM Quick Tips publications in our office or online about each of these pests. Or, you can call or email your local UC Cooperative Extension Master Gardener Program. For Stanislaus County residents, click on this link to submit your question along with photos if you have them:http://ucanr.edu/ask/ucmgstanislaus

 

4. Why are my oranges splitting?

The reason this happens is not well understood, although it's often related to changes in weather conditions. However, allowing the soil to dry out too much between irrigations is believed to result in increased splitting. Make sure your tree has a constant supply of moisture by watering monthly during the dry season.

 

5. When should I prune my orange tree?

To be honest, nobody has asked this question. However, Ed and I think they should! The answer is the opposite of what most gardeners think. THE BEST TIME TO PRUNE CITRUS IS IN SPRING!

When pruning deciduous trees like peach, plum or cherry, after leaf drop, don't be tempted to prune citrus! Citrus trees are evergreen and require little if any pruning except to control size. If you'd like to keep a new citrus tree under 5 feet tall, you can carefully prune it in spring to manage the height. This way, you won't need a ladder to pick fruit again!

Avoid pruning in fall or winter, which encourages new growth favored by pests and can leave the tree susceptible to frost injury.

 

*if your tree leaves turn yellow and it's not winter, this may be a different problem.

 

The colors of autumn are especially beautiful this year. Tree leaves are turning brilliant shades of yellow, orange, and even purple.

Want fall color in your landscape next year?

Read about the trees you've noticed around town that are currently “popping” with color. And, if you plant a tree now (or in early spring), you can have fall color in your landscape next year! Here are some excellent tree species to choose from that thrive in our area (USDA Zone 9b):

Chinese Pistache – Pistachia chinensis

The Chinese pistache is Ed Perry's favorite tree. Ed was the Environmental Horticulture Advisor for over 35 years at UC Cooperative Extension in Stanislaus County. He chose this tree not only for its fall color, but because it produces good shade and has “well-behaved” roots. Opt for the male cultivar ‘Keith Davey.' Female cultivars have colorful berries which although pretty, are considered messy and not suitable for over a patio.  

Height: 30-50'
Light needs: Plant in full sun.
Water needs: Moderate. Does well in lawns.
Note: You can't go wrong with this tree! Also, it is not closely related to the nut bearing pistachio tree.

Maple Trees – Acer rubrum

Cultivars like ‘October Glory' or those with the name ‘Autumn' in their title promise fall colors. Suitable to plant near sidewalks, these trees also have well-behaved roots that aren't disruptive to infrastructure. Just remember, this tree needs to be watered regularly in summer, otherwise the edges of the leaves will turn brown.

Light needs: Plant in full sun or partial shade.
Height: 40-50'
Water needs: Regular water. Does well in lawns, but water separately from the lawn.
Note: Sprinkler water will not be enough for this tree.

Bradford Flowering Pear – Prunus calleryana ‘Bradford'

This flowering pear has cheerful white blooms in spring and produce fall color during cool winters. Their roots are well-behaved so they can be planted near sidewalk. Please note, many cultivars of flowering pear have problems such as mistletoe and fireblight. Make sure you choose a Bradford pear. After bloom, this tree does drop small fruits that are messy.

Height: 40-50'
Light needs: Plant in full sun.
Water needs: Moderate. Does well in lawns.
Note: although bred to be fruitless, the Bradford pear cross pollinates with other pears which is why it produces inedible “fruit.”

Japanese Maple Trees – Acer palmatum

If you have a partially shady spot and want a small tree, Japanese maples make a great choice. Tree leaf and bark color varies among the hundreds of cultivars available. ‘Burgandy' has purple leaves, ‘Sango Kaku' has coral-colored bark, and ‘Aoyagi' has bright green bark.

Light needs: Plant in partial shade, some species (‘Emperor One') are adapted to full sun.
Height: 6-20', varies. Do some research before choosing your tree.
Water needs: Regular water.
Note: This tree can give year-round interest!

Ginkgo – Ginkgo biloba

This ancient tree existed long before dinosaurs roamed the earth. In fact, fossils of gingko leaves have been discovered from the Jurassic period! Ginkgo trees leaves turn a beautiful golden color in fall. Choose a male cultivar such as ‘Saratoga' or ‘Autumn Gold.' Female cultivars produce fruit that some people consider unpleasant.

Light needs: Plant in full sun.
Height: 30-50.'
Water needs: Moderate water; can tolerate drought but won't look healthy.
Note: Excellent street or patio tree, also does well in a lawn.

Liquidambar – Liquidambar styraciflua

You'll need a large space for this towering tree that reaches up to 60' tall. If the roots are given enough space to grow, it makes a fantastic street tree that provides excellent shade. Disclaimer: although the leaves are colorful and beautiful, the tree produces copious amounts of seed “balls” that ruin the experience of jumping into a pile of raked leaves. Choose ‘Rotundiloba' which grows more slowly and rarely produces the spiny “balls.”

Light needs: Plant in full sun.
Height: 50-60.'
Water needs: Regular water.
Note: Surface roots can crack sidewalks and come up in lawns.

Tree Notes – Choosing a Tree

When choosing a tree, look for one with leaves growing along the entire stem. Avoid trees that resemble a mature tree (with a long stem and a heavy top). The leaves are necessary to help the tree develop a strong trunk.

Tree Notes – Planting

Planting a tree correctly is essential to having a healthy tree. Follow these steps:

Step 1: Remove the tree stake.
Step 2: Dig a hole twice as wide but the same depth as the container.
Step 3: After removing the “root ball” (area of soil and roots) from the container, set it in the hole.
Step 4: Make sure the top of the root ball is lined up with the surrounding soil or a little higher.
Step 5: Fill in around the root ball with removed soil, do not cover over the root ball with soil. Make sure the root ball is still showing and is level with the ground.
Step 6: Create a basin around the base of the tree and water well.

Tree Notes – Staking

If you remove the stake from your new tree and it falls over, return the tree. Healthy trees should not fall over and do not need to be staked. In fact, a tree that can't stand upright that grows into a mature tree is likely to become a landscape hazard** in the future.

Allowing your new tree to sway with the wind helps it develop a strong trunk and root system. The only time it is recommended to stake trees is in areas with heavy wind. In this case, two stakes should be used, and then removed after one year. Learn more about tree staking in the Planting Landscape Trees publication below.

Tree Notes – Water

All newly planted trees need regular water for the first 2-5 years after planting. Regular water means keeping the soil moist but not too wet or allowing it to dry out. Once their roots are established, trees need deep water once or twice per month during the dry season (May-October), depending on temperature, tree species, soil type, and other factors.

Resources

Stanislaus County Tree Guide

Looking for more tree recommendations? Visit our publications page and scroll to the bottom of the page to click on our “Trees in Your Home Garden” publication at https://cestanislaus.ucanr.edu/Gardening_Publications/

Planting Landscape Trees

https://anrcatalog.ucanr.edu/pdf/8046.pdf

 

*University research has shown that adding amendments such as compost and fertilizer to planting holes does not help trees; in fact, it can cause problem. Read more at https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=46215

**worried you may have a hazardous tree in your landscape? Download this free guide for tips on how to inspect it. https://anrcatalog.ucanr.edu/pdf/8365.pdf