Please join us for the 7th Annual Citrus Field Day, designed for citrus growers and citrus industry representatives. Pending approval, we will be offering 5.0 hours of California Continuing Education Credit for Pest Control Advisers (PCA).
Date: December 15, 2018
Time: 9:00 AM - 12:00 PM
Contact: Jasmin Del Toro: 559-592-2408 ext 1151
Sponsor: Lindcove Research and Extension Center
Location: Lindcove Research and Extension Center
The general public is invited to join us for a family friendly Citrus Tasting Event. You can see and taste more than 100 citrus varieties that are grown at Lindcove Research and Extension Center. Take a bag of fruit home for $10. Choose from Cara Caras, Navels, Mandarins, or assorted citrus from 4 bins located in front of the Conference Center. The Master Gardeners as well as UC Cooperative Extension Advisors will be happy to answer questions from home gardeners and citrus connoisseurs.
Directions: Take Highway198 east to Mehrten Drive (approximately 15 miles) and follow the signs to our Event. The University of Lindcove Research and Extension Center is located at 22963 Carson Avenue Exeter, CA. The Conference Center is located at the end of Carson Avenue. If you have any questions please contact Jasmin Del Toro at 559-592-2408 Ext 1151 or firstname.lastname@example.org
Register for 2018 UC Riverside Citrus Day for the Industry
- Author: Vanessa Ashworth and Philippe Rolshausen
Department of Botany and Plant Sciences, University of California Riverside.
Evidence of avocado selection by human hand as far back as 8,000 BC is preserved in archaeological sites in Puebla State, Mexico. At the time of European contact, written records indicate that there already existed three distinct types of avocado, each from a separate geographic center of origin. Today, we refer to them as botanical races, and they represent the “primeval soup” that gave rise to modern avocado cultivars. Here is what we know about the three botanical races of avocado, respectively called (1) the West Indian (formerly known also as the South American), (2) the Guatemalan, and (3) the Mexican (also known as the “criollo”): Each exhibits a characteristic suite of traits that includes differences in leaf chemistry (a distinctive anise scent is found only in Mexican race avocados), peel texture and color, fruit oil content, and sources of tolerance (diseases and salinity). The races were domesticated in separate geographic regions, the “West Indian” race in lowland coastal Mesoamerica (possibly Yucatán), the Guatemalan race in upland Guatemala, and the Mexican race in highland Mexico. The Guatemalan and Mexican races remained fairly local, so their names reflect their respective centers of domestication, but the “West Indian” race seems to have been spread far and wide by indigenous cultures in Meso- and South America and was, incorrectly, named for a much later destination. The explorations of the 15th and 16th centuries kicked off the worldwide distribution of (mostly West Indian race) avocados, reaching Spain in the early 17th century, Jamaica in the mid-17th century, and Indonesia by the mid-18th century. It wasn't until the mid- to late 19th century that the three races of avocado found their way to the United States, primarily Florida and California, where they underwent many rounds of selection and hybridization. ‘Hass', the cornerstone of the California avocado industry, was patented in 1935 but its ancestry is unknown. It is considered to be a Mexican x Guatemalan hybrid because its leaves lack the anise scent and its fruits combine the thick, rough skin of the Guatemalan race but the high oil content of the Mexican race.
Avocado is a fruit tree that is notable for its sensitivity to cold. There are tropical varieities that are very sensitive to cold most notably many of the varieties that are of a West Indian origin. The subtropical varieites that are grown in California are of Mexican and Guatemalan origin or hybrids of these two subraces. ‘Hass' is a variety that has genetic origins of both of these subraces. Mexican origin typically have more cold tolerance than Guatemalan sources. Mexicans can often sustain cold down to the mid-20 deg F for a few hours when trees are mature. Young trees can sustain short periods under 30 deg but can be severely damaged or killed for prolonged times (more than 2 hours). Temperature and duration are not the only factors for determining damage potential. Humidity, wind and surrounding environments (proximity to open water, enclosed areas with reflective heat, etc.) are also important factors.
We know from experience that some varieites of Mexican origin are more cold tolerant than other varieites, some being able to the very low 20's for prolonged periods are survive. They may not produce fruit the following year because all the fruiting wood may be killed, but they will still come back. Varieties like ‘Bacon, ‘Zutano', ‘Stewart', ‘Susan' and even ‘Fuerte' are notable for their greater cold tolerance than ‘Hass'. They may not have the same eating and shipping qualities as ‘Hass' so they will not be commercialized on the scale that ‘Hass' has. But some people like these lower oil content fruit.
It recently came to my attention that there are some low chill avocado varieties that were selected in Texas where winter temperatures are usually killing for most of the avocado varieites we have have. Texas has a much smaller acreage of avocados than California and even Hawaii. So small (under 500 acres) that yields are not recorded for this crop. Most of the trees are backyard trees that have much more protected environments than a normal orchard setting. No really systematic data has been collected on their cold tolerance, but word-of-mouth has identified several varieties that might be cold tolerant. These are ‘Holland', 'Wilma', ‘Joey, ‘Fantastic', ‘Lila' and ‘Poncho'. They may not be the best tasting (that is in the opinion of the taster, as always), the best shipping (thin skinned and damage easily), or hang on the tree for a long period of time, but may make for a good backyard tree in colder environments. There has been no systematic study to determine if and which of these varieties might be more cold tolerant that those that we already are growing in California. Desperate gardeners might find them worth growing in marginal environments.
The avocado as an evergreen subtropical will never likely be a commercial tree in Canada (greenhouses?) but there may be more cold tolerance in the species than we normally associate with the crop. For a description of some of the characteristics of the Texas industry see the bulletin: http://aggie-horticulture.tamu.edu/fruit-nut/files/2015/04/avocados_2015.pdf .