Editor's note: Today's author is in Texas Master Gardener training for Home Fruit and Nut Tree Specialist - Southern Texas 2017, which serves as a major source for this article. Since there have been various articles published previously on citrus and recently on persimmon in this column, other various fruit and nut trees are included in today's publication.
When buying a fruit or pecan tree, one of the first questions people ask is, "Do I need one or two trees?" Some fruit trees are self-fertile, while others require a pollinator. We might think that means a second tree of the same variety, but choosing an appropriate pollinator is more complex, with each type of tree having specific requirements.
It's important to select the right trees for our climate, keep our trees healthy and understand pollination issues. These factors are interrelated with one problem causing another, resulting in minimum crop yield - or none at all.
Let's evaluate some fruit and nut-bearing trees and their pollination requirements, starting with simple self-fertile trees and moving on to more complex variations.
Self-fertile
- Peaches (and chilling requirements)
Since peaches are self-fertile, with each flower having male and female parts, only one tree is needed. Pollination of peaches is easily accomplished with minimum motion from wind or bees.
Choose a variety with chilling requirements close to the average hours of chilling for your location. A simplified definition of "chilling requirement" is the number of hours at or below 45 degrees, beginning in November, which would be required for a tree to break dormancy. Average chilling hours have been determined for each county.
If the hours of actual chilling in an area exceed the hours required by a specific variety of tree, the tree is likely to bloom too early and risk chance of freezing. If the hours of actual chilling are less than the hours required, the tree won't properly break dormancy, resulting in poorly formed flowers and few, if any, peaches.
Figs are self-fertile but don't have chilling requirements. Note that a tree's "chilling requirement" and tolerance of temperatures below freezing are two separate issues.
Most varieties of citrus are self-fertile with a few exceptions.
Pomegranates are self-fertile, but cross-pollination by insects increases fruit production. High humidity can interfere with fruit formation.
Olives
Olives are self-fertile, but according to Monte Nesbitt, TAMU Extension Fruit Specialist, one of the many problems with growing olives in our Coastal Bend region is that temperatures by blooming time may create loss of fertility.
Some variations
Pear trees require appropriate chilling and cross-pollination; that is, pollination by a second tree of a different variety blooming at the same period of time. Thanks to bees, some varieties may still produce fruit without that second tree in your backyard. Disease susceptibility further limits the varieties of pears grown in our Crossroads area.
Apples have more pollination challenges than pears, including: appropriate chilling, cross-pollination by a different variety in close proximity, blooming at the same time and substantial bee activity to the extent that commercial growers maintain their bees.
Although I grew up on a farm with lots of pecan trees, including many grafted by my grandfather, I never gave much thought to pollination of pecans necessitating more than one tree. But there are definite requirements because of separate male and female flowers borne on each tree.
A Type I tree (protandrous - with pollen shedding first) should be paired with a Type II tree (protogynous - female flowers receptive first), which need to be pollen shedding and pollen receptive at the same time. Good selections can be made based on pollination charts that set out the timing of shedding and receptivity for various Type I and II cultivars.
If native pecans are within sight of your planting location, you may not need to purchase a second tree for pollination, since it is assumed that about half the native trees are Type I and half are Type II.
Increase chances of successful pecan yields by selecting varieties designated for East Texas and with excellent pecan scab resistance. Weather conditions in this area are conducive to the spread of this fungus, which can decimate your pecan crop.
Climate can determine whether or not avocados need a cross-pollinator. For example, in California, a cross-pollinator is necessary, matching a Type I and Type II tree; however, in South Texas, climate generally creates some overlap in Type I and II conditions allowing avocados to self-pollinate.
Choose tree variety based on factors
Knowing whether to choose one or two trees is not the only factor for maximum fruit and nut production. Choose the appropriate variety of tree for your area based on climate, chilling requirements and disease resistance coupled with a suitable pollinator if applicable.
Do some research to determine the best choices. Keep your trees healthy. Use pesticides judiciously for the protection of bees that are vital for successful pollination and production of fruit.
The Gardeners' Dirt is written by members of the Victoria County Master Gardener Association, an educational outreach of Texas A&M AgriLife Extension - Victoria County. Mail your questions in care of the Advocate, P.O. Box 1518, Victoria, TX 77901; or vcmga@vicad.com.
Victoria County Master Gardener Association
