Ventura County UCCE Farm Advisor Ben Faber shares with us some of his citrus tree knowledge.

Heat affects different types and varieties of citrus differently. Heat determines when fruit ripens and how sweet it will be.  Grapefruit has one of the highest heat requirements of all citrus.  Grown along the coast it will be sour, but in the Central Valley it can be decidedly sweet.  A Pixie mandarin along the coast will be 6-8 weeks later in ripening than the Valley and will hang on the tree much longer.  Acid fruits like lemon and ‘Bearss’ lime have low heat requirements and are well adapted to the coast.  The everblooming characteristics of lemons and limes are accentuated along the coast where there may be continuous cropping with lemon blooms year round.

High temperatures can have a negative effect on citrus.  Coastal citrus may suddenly drop fruit when temperatures swing from the cool 60’s to the 90’s as often happens with Santa Ana conditions.  Sudden warm weather can cause fruit to split, induce flower and leaf drop, and cause sudden burn to both the fruit and tree.  These problems are compounded by dry soil moisture and problems can be reduced if there is adequate moisture present during the heat wave.  In hot environments, some citrus like navels produce less fruit.

Lemons

As with many things in life, chances for long-term success with citrus are increased with knowledge and planning. Even the size of the plant put in the ground has an impact on long-term growth and return on investment. Ventura County UCCE Farm Advisor, Ben Faber shares his knowledge with us.

What size plant should I buy?

The longer the plant has been in the container, the longer it takes for the plant to adjust to the soil after it has been planted.  The smaller the plant, the more rapid the growth once it is put in the ground and survives -- a 5 gallon container- grown lemon will have outgrown the 15 gallon container in 3 years.  This has been shown consistently with all manner of container grown plants……..and they are cheaper.

One vital consideration is the type of variety to plant. Please remember to use only rootstocks that are California-grown certified trees that are known to be free of disease. It is illegal to bring in citrus trees or cuttings into California from other states or countries because they may be infected with disease or insects.

Rootstocks

There are many different rootstocks available to growers.  Choose rootstock based on characteristics that are important to the growing site, such as greater nematode resistance, salt resistance, disease resistance, etc.  The retail nursery typically sells whatever rootstock the wholesale nursery propagates. Wholesale nurseries do not all use the same rootstocks, but use those that they feel grow best for them.  In some cases, a retail nursery may be able to special order a rootstock for a special situation.  You can always ask.

There is one choice that the buyer can make, though – whether the rootstock is dwarfing or not.  The ‘Flying Dragon’ rootstock creates small tree, under 6 feet and it is very slow growing.  It especially lends itself to container culture.

For home growers, another important consideration is where to plant the trees. Irrigation needs are an important piece of this puzzle. Keep the following in mind while looking for a planting location:

Growing citrus in a lawn

Trees don’t belong in lawns.  In California, we irrigate.  Do you irrigate to the needs of the lawn or to the tree?  Frequently, lawns are irrigated by timers, putting a short burst of water on.  Trees like a deep watering.  Shallow watering leads to an accumulation of salts in the tree’s root zone and salt burn results.  If possible, keep a 6-foot turf-free area around the trunk.  And best of all, irrigate the tree separately from the turf and ensure the lawn sprinklers do not wet the trunk, which can lead to crown rot in the tree.

Citrus can be grown in containers. Ben offers the following suggestions for the best results:

Container grown citrus

Citrus grows well in containers, especially if you choose varieties like ‘Meyer’ lemon which is a less aggressive tree or use ‘Flying Dragon’ dwarfing rootstock on one of the other citrus varieties.  There is a long history of orangeries in Europe, where full sized trees were grown outside in containers in the warm weather and then moved into large greenhouses when it got cold. Half barrels and terra cotta pots can be used, but if a large container is used and you want to be able move it, put the container on some wheels first.  Fill the container with a good quality potting mix and plant your tree.  Containers dry out much faster the soil grown trees, so stay on top of the irrigation.  When irrigating, make sure water comes out of the bottom of the pot to avoid salt accumulation in the root zone.  Prune as necessary to keep the canopy in balance with the pot or pot up to the next size.

Additional information can be found on the Ventura County UCCE website.

Healthy citrus

Ventura County University of California Cooperative Extension (UCCE) is here to extend science-based research to people in our community. We do this in a variety of ways, one of which is newsletters.

Landscape Notes is written for people working in the commercial landscape industry. The last issue is all about establishing landscape trees. It is full of fabulous, practical information that will help establish healthy trees.

Clover Lines is a newsletter published for 4-H members and leaders in Ventura County. It contains events, activities, and opportunities for youth aged 5-19.

Topics in Subtropics is a combined effort by University of California Cooperative Extension Farm Advisors from many counties in the state. It emphasizes citrus and avocado, but also discusses the minor subtropicals. The last issue covered:

• Avocado Research in Ventura County
• Laurel Wilt Disease Conference and Tour in Florida and Georgia
• Managing Insecticide Resistance will be Key to the Future of Effective Citrus Pest Management
• Smart Sprayers Make Sense

Farm Water Quality News delivers the latest news on integrating environmental quality with crop production practices. The last issue covered:

• Regulatory Update
• Industry Update
• Technical Tips
• Research Update

UC Cooperative Extension Report is our department newsletter. This newsletter includes upcoming events, highlight summaries of research and outreach activities, interesting facts and more.

Santa Clara River Watershed Times covers topics vital to anyone who lives, works, and recreates in the Santa Clara River watershed, the largest river system in Southern California. An amazing amount of information is extended in this newsletter covering a wide range of issues, opportunities, regulations, and accomplishments in an easy to read format with great photos. Links for more information are scattered throughout.

Our newsletters can be found by clicking this link. Once there, you can read current and back issues. You can also sign up for email notification to let you know when a new issue has been posted.

The tiny Asian citrus psyllid (ACP) has the potential to wipe out the California citrus industry. It is a carrier of the deadly bacterial plant disease, Huanglongbing (HLB), which is also known as citrus greening disease. This disease is fatal to citrus trees.

The insect feeds on citrus leaves and stems. Unfortunately, ACP has already been found at several sites in California. It threatens not only the commercial citrus industry, but also the ability of California residents to grow citrus at their homes.

It can take years for the symptoms of HLB to appear. Inspection and elimination of ACP is our first line of defense. Signs of disease include: asymmetrical yellowing and splotching of leaves; new growth is misshapen and twisted; produces bitter, inedible, misshapen fruit.

To help stop the spread of this insect and disease: inspect trees monthly and whenever watering, spraying, pruning or tending to trees; plant only certified disease-free citrus trees from a reputable nursery; do not bring any plant material into California from other states or countries.

At the end of this post you will find a presentation from the Citrus Research Board, provides additional information and photos. Topics covered include: other plants that can be attacked by the psyllid; maps showing locations of pest and disease; ways that the pest moves around; what happens when ACP is detected; how an infestation affects commercial citrus orchards.

If you find the Asian citrus psyliid, call the CDFA hotline at 800.491.1899 right away.

To learn more about the Asian citrus psyllid and HLB disease, or to download printed materials in English, Spanish and Chinese, please visit www.californiacitrusthreat.com.