Reading Avocado Trees During the Winter

Winter is not a quiet time for California avocado trees, as was once thought. In fact, a great deal happens within the avocado tree over winter that determines how well the trees flower and set fruit in spring. Over winter the avocado trees can develop flower buds, continue to size fruit, the fruit accumulate dry matter, roots can grow and some types of sugars can accumulate. Winter weather can also strongly influence the way the avocado trees develop flowers and are set up for fruit set in spring.

For an avocado grower, following flower bud development through winter can be part of a proactive avocado cultural management process.  It allows the grower to anticipate problems and opportunities. Careful observation of the growth and development occurring on avocado trees, even during seasons when the trees appear to be doing little, can be used to indicate what cultural management activities are needed for the best yields.

Avocado flower development in winter

• In winter, quite a bit of flower development within the flower buds occurs. However, once winter is here, there is not much a California avocado grower can do to influence how many flowers there will be in spring. The hard work needs to have gone into the trees before winter sets in.
• If the winter has warm spells, some flowering and fruit set can even occur. This should tell the grower that despite the cooler weather, the trees are primed for flowering and fruit set should weather and avocado grove conditions be favorable.
• Winter development of the flower buds on shoots is influenced by when the shoots grew in spring, summer or fall and internal tree factors. The latest research indicates that a heavy crop on the trees, means less flowering in the spring because the flower buds don’t break in spring.

Monitoring flower buds on avocado trees during the winter

• By the end of November flower buds should be visible on the avocado trees. Take note of the  change in shape and size of the buds through to flower bud break. The buds to look for are located where the leaf stalk is attached to the shoot and start at the tip of the shoot and go back down towards the main branches.
• Vegetative buds are small and triangular in shape while flower buds are round and plump.
• Most of the flower buds are clustered at the tips of shoots and in the joints of the first five to six leaves on a shoot.
• The majority of flower buds are found on the warmest and sunniest parts of the tree.
• If the trees are tall it will not be easy to see where most of the flower buds are, as flower development is likely to be concentrated at the tops of the trees.
• Small trees, well exposed to light all around, are more likely to develop flower buds all over the tree and it is easier to see how many flower buds there are.

Basing avocado grove cultural management decisions on flower bud development

Having a good idea how many flower buds are developing and the progress of flower bud growth are useful pieces of information for growers in their decision making. By determining if flowering will be stronger than expected a grower can alter harvest timing decisions.

If the flowering is heavy:

• the fruit will compete with the flowering and new fruit set
• bees may need to be placed in the avocado groves earlier and in greater numbers
• trees can fail to grow enough new fruiting wood resulting in a poor return crop
• trees may need to be pruned in order to better balance flowering to shoot growth for the following year.