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!
- Author: Anne Schellman
- Author: Ed Perry
- 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.
- How do I know if my oranges are ripe/when should I pick my oranges?
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.
- What is this pest?
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.
- 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.
- When should I prune my orange tree?
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.
- Author: Anne Schellman
- Editor: Roger A Duncan
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
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
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
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
/h3>/h3>/h3>/h3>/h3>/h3>/h3>/h3>/h3>/h3>/h3>/h4>- Author: Anne Schellman
The trees around the Ag Center are Oklahoma Redbud trees (Cercis canadensis ‘Oklahoma'). This tree has a “cousin” that is a CA native, called the Western redbud, (Cercis occidentalis) which you may have noticed is blooming in the foothills.
Redbud trees may be single stemmed or multi-trunked trees. Both grow quickly and have heart-shaped leaves that turn golden in fall. They make an excellent street or patio tree since their roots do not disturb the sidewalk.
Both trees need regular water for the first few years until they are established. Once established, the Oklahoma redbud tree needs moderate to regular water, while the Western redbud tree needs less.
Thinking about planting a redbud tree? Spring is a great time! For tips on how to plant a tree, see our post, Planting and Pruning Ornamental Trees at https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=30091
Here are the resources mentioned during the talk.
Citrus varieties
https://citrusvariety.ucr.edu/citrus-varieties
UC IPM website https://ipm.ucanr.edu/PMG/menu.homegarden.html
Ants
https://ipm.ucanr.edu/PMG/PESTNOTES/pn7411.html
Selected Citrus Varieties for the Home Gardener https://anrcatalog.ucanr.edu/pdf/8472.pdf
Grafting and Budding Citrus and Avocados in the Home Garden
https://anrcatalog.ucanr.edu/pdf/8001.pdf
Forestierre Underground Gardens in Fresno, CA
https://undergroundgardens.com/