An Iconic State Fruit
The first citrus trees were planted in southern California’s bountiful mission gardens not long after the state was first settled in the late 18th century. Tracy Kahn from the University of California, Riverside highlights the history of citrus in California and the start of the Citrus Variety Collection in Riverside. Throughout the 1800s citrus trees became more prolific in The Golden State and orange groves popped up in what is now bustling downtown Los Angeles. Fast forward 150 years and California is now the nation’s leading supplier of fresh oranges, lemons and mandarins. It is estimated that more than half of all California residences have a citrus tree on the property.
Citrus is part of California’s cuisine, landscape and economy. Commercially grown citrus contributes $7 billion in economic value and employs more than 22,000 individuals in California. The incurable and fatal plant disease Huanglongbing threatens to erase this tradition from our state’s history and put thousands out of work. We must act now to protect California citrus.
How to Grow Healthy Citrus
Citrus trees are a beloved plant choice for home gardens in California and it’s no surprise why. Citrus trees have shiny, green leaves, delightfully fragrant white blossoms, and colorful fruit you can juice, preserve or eat fresh.
If you’re considering putting a citrus tree on your property first be sure to get your plant from a reputable, licensed nursery in your area – and recognize you need to manage pests and diseases on your tree throughout its lifetime. To graft citrus onto an existing tree variety, get registered budwood that comes with source documentation. These best practices will make sure you don’t accidentally get a tree infected with Huanglongbing.
To grow healthy California citrus, follow these tips:
- During the first year, apply water at the tree’s trunk. As the tree grows, water a larger area around the tree. Newly planted trees should be watered every three to seven days, and older trees can be watered every week or two.
- Apply fertilizer, including nitrogen, phosphorus and potassium, to soil throughout the year. Zinc or iron deficiencies can result in yellowing leaves, so monitor and apply a foliar spray of zinc or iron if needed.
- Most citrus varieties do not require significant pruning. Lemons are the exception to the rule. Heavy pruning should not take place in winter as it will make trees susceptible to frost damage.
- Inspect for the Asian citrus psyllid and Huanglongbing, and other pests and diseases, monthly or whenever watering, spraying or pruning trees. Pest and disease management is crucial to protect not just your own tree, but also your neighbors’ trees and the state’s citrus.
- Control for ants on your citrus tree. Ants protect harmful pests like the Asian citrus psyllid. Place ant bait around citrus trees, and follow the product’s label instructions.
- When harvesting fruit, clip the fruit off at the stem with sharp clippers. Remove leaves and stems, and wash fruit thoroughly to ensure no Asian citrus psyllids or Huanglongbing-infected plant material is spread. Obey quarantines in your area.
Huanglongbing affects all citrus plants, including orange, lemon, lime, mandarin, pomello, kumquat, grapefruit and tangerine trees. It also affects some relatives of citrus, like orange jasmine and curry leaves. If you have any of these plants in your yard, inspect them when trees have new leaf flush, or when tending trees. If you think you’ve found in the Asian citrus psyllid or Huanglongbing, call the statewide hotline at 800-491-1899.
Florida: A Fading Citrus Star
California may lead in fresh citrus fruit production, but Florida reigns king of citrus juice. Orange juice has been a staple on breakfast tables for generations. Unfortunately, Huanglongbing, also known as citrus greening disease, has spread throughout Florida. Citrus trees are dying at alarming rates. Thousands of jobs have been lost and the economy is suffering. Florida growers are doing everything they can to save their citrus trees, but researchers have not yet found a long-term solution to the disease.
This graph shows the decline in Florida citrus production due to diseases like Huanglongbing and citrus canker, hurricanes and other factors. Data was gathered from USDA, National Agricultural Statistics Service, and is accurate as of March 2016.