FLOWERING AND FRUITING IN OLIVES IN SUBTROPICAL CLIMATE WHERE OLIVES NORMALLY GROW VEGETATIVE

Authors: Malik, Nasir; Bradford, Joe

Submitted to: International Journal of Fruit Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2004
Publication Date: 7/19/2006
Citation: Malik, N.S., Bradford, J.M. 2006. Flowering and fruiting in olives in subtropical climate where olives normally grow vegetative. International Journal of Fruit Science. 5(4):47-56.

Interpretive Summary: Historically, flowering and fruiting in olives does not occur in southern Texas. However, we have achieved normal flowering and fruiting in 'Arbequina' olives in Weslaco, Texas, by simple treatments such as periodic sprinkling of water on the plants or by simply shading the trees under dry or wet tents during winter months. This is an important achievement because it provides hope and understanding that such cultivars of olives could be adapted to climatic conditions of coastal areas of several Gulf states where daytime temperatures during winter do not exceed 20ºC. The idea of such treatments was developed from our previous findings where it was established that lack of flowering in southern Texas was not due to insufficient chilling (chilling is defined as an average temperature of 7.2ºC or below during the night). Rather, lack of flowering is due to daytime temperatures that are too high (above 20ºC). Thus, we hypothesized that a few degrees of cooling during the day, by shading or evaporative cooling, should allow flower and fruit development in olives growing in Weslaco, Texas, and the results described in this report confirmed our hypothesis. Potential benefits of these results are that thousands of acres of currently uncultivated land in coastal areas could be developed for olive cultivation.

Technical Abstract: It is generally presumed that lack of flowering and fruiting in olives in subtropical climates of southern Texas (e.g., Weslaco, Texas, area; N 26.16° Latitude, 97.96° Longitude) is due to fewer chilling days ('7.2ºC) during winter than most olive growing areas of the world. However, using controlled environmental chambers, we have recently shown that flowering and fruiting in the 'Arbequina' cultivar of olives can be achieved without any chilling days ('7.2 ºC). This raised the question of why olive trees don't flower in southern Texas that do experience some chilling days. We hypothesize that absence of flowering in olives growing in southern Texas, and in a similar climate elsewhere, is due not to lack of enough chilling days ('7.2ºC during night), but most likely due to high temperatures during the day ('23ºC) that inhibit flowering. To test our hypothesis, we provided cooling to olive trees growing under the Weslaco, Texas, climate by simple shading or by evaporative cooling. These treatments resulted in good flowering and fruiting in 'Arbequina' olives in Weslaco, Texas, after a typical winter period, although normally olive trees in this subtropical climate remain vegetative even after winter months.