One avocado tree can produce a lot of fruit

Can you tell me once and for all, do I need to plant two avocado trees so they can pollinate each other and produce more fruit?

Some people have told me I need to plant two types of trees. If so, what are the types? Others have said it doesn’t matter.

Avocado varieties are categorized as A and B flower types. All avocado flowers have both male and female components (stamens and pistil), but an unusual and unique facet of avocado flowering is that they open as a male flower at one time of the day and open again as female at another time.

Here is the scenario: A-type flowers open female in the morning, close, then reopen as male in the afternoon. B-type flowers are male in the morning and female in the afternoon.

This works out very well in a garden with both A- and B-type trees. In the morning, the female A-type flower will be pollinated by the B-type males. And in the afternoon, just the opposite will occur.

If there were only one type of avocado tree present in the garden, it is possible that little fruit would be produced. This statement would be true if it were not for the presence of bees efficiently distributing pollen.

In addition, there is usually, although not always, the opposite type tree somewhere in the neighborhood. The bottom line for backyard growers is that in most cases one tree will provide ample fruit.

For commercial growers, much research has been conducted, and it is widely accepted that fruit production can be helped with the presence of a tree of the opposite type flower. CTAHR has an excellent publication available online and at the Komohana Ag Center, “What Makes a Good Avocado Cultivar Good?”

Table 2, in this publication shows various avocado cultivars grown in Hawaii and their flower type. For example, the Sharwil variety which has a bearing season of winter-spring, is a B flower type. Greengold (winter-spring) and

Ohata (summer) are both A flower types. For new readers, CTAHR stands for College of Tropical Agriculture and Human Resources found online at http://www.ctahr.hawaii.edu/site/info.aspx.

Nick, I have had a problem with white fly in my greenhouse in the past so I have not planted anything in it for a couple of years. Now I want to use it again, but I was told that the eggs of the white fly are in the soil and the soil will have to be replaced. Is this true? If so, is there anything short of replacement can I do? Over the years, I’ve tried so many things, nothing worked. Do you have any suggestions? Much mahalo!

You do not have to replace the soil! Whitefly eggs will not survive in the soil for one to two years. They usually hatch in six to seven days and are not laid in the soil but on the plant.

Whiteflies do have the potential to re-infest the greenhouse by simply flying in again. In fact they can gain access to the greenhouse crops through various means: 1. from new plants or cuttings which are brought into the greenhouse, 2. from infested plants outside and near the greenhouse; 3. they may already be there infesting weeds growing in the greenhouse; and 4. people moving in and out of the greenhouse can also carry adult whiteflies on their clothing.

It would be a good idea to hang some yellow sticky cards around the greenhouse and periodically inspect them. The cards will attract the whitefly, and they will become stuck. The cards are a monitoring tool for early detection and thus early treatment.

Certain measures can be taken to delay whitefly infestation such as weed control and minimizing greenhouse access. Yet it might also be wise to assume that the greenhouse will eventually become infested and prepare to implement control measures at the proper time.

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at askthegardenguy@earthlink.net. You also can visit his website at www.gardenguyhawaii.com.