Q. I have an Oroblanco mini grapefruit along with other citrus growing in my backyard. All of them have flowered and set fruit except for this grapefruit. My friend has one of these too and hers has given her fruit. What do I do to get this finiky grapefruit to produce fruit?
A. If your backyard does not get too cold then it should produce well for you. Citrus biggest problem here is winter cold damage, freezing back and late spring frosts that eliminate flowers and fruit.
Grapefruit is one of the citrus that has the best potential for Las Vegas but Oroblanco is a grapefruit and pomello cross. It may be a bit more sensitive to winter cold and late freezes than traditional grapefruit like Marsh or Ruby Red.
Oroblanco is harvested in the fall when temperatures are dropping around October. It is this time it has its best color and flavor.
It flowers in the spring. The tree should be loaded with flowers if there have been no freezing temperatures. About 2% of all the flowers will result in fruit. The rest of the flowers and young fruit are aborted by the tree.
The flowers give way to fruit as long as freezing temperatures don’t kill the flowers or young fruit during spring months. Flowers and young fruit are extremely sensitive to any freezing temperatures while the tree itself is much more tolerant. The flowers or flower buds will be killed but you may see no damage to the tree.
The other possibility is spring pruning. Citrus in general are seldom pruned unless it is needed. Excessive pruning in the spring can remove spring flowers before they come out. Pruning can also result in no flowers and no fruit. It is best to prune these trees just after harvest in October.
Irregular watering can cause the tree to drop flowers and fruit. Use a surface wood chip mulch to help keep the soil moisture from fluctuating too much and fruit/flower drop.