It would appear that the pomegranate is among the healthiest health foods on earth.
Hundreds of peer-reviewed articles in scientific journals attest to the multi-faceted benefits of pomegranate consumption, from lowering cholesterol and improving heart function to the prevention and mitigation of cancer, diabetes, and Alzheimer's disease. Pomegranates are the last deciduous tree fruit to be harvested during the year and they are reaching their peak ripeness now. You need to harvest them before they split - yet how will you know when the moment is right to pick them?
Regarding pomegranates, there are a number of ways to measure readiness for harvest. Tap on the fruit several times and a metallic sound indicates they should be picked. Alternatively, do a scratch test; when unripe, a pomegranate skin is tight and resists scratching but when ripe the skin softens and, with a little pressure, the peel can be scratched. Put the fruit in your hand; it should feel heavier than its size would indicate, a condition that exists when ripeness arrives and the arils (seeds) -- from 200 to 1,400 in a single fruit -- are full of juice. (Note: pomegranate comes from two French words, pomme, meaning apple, and grenate, meaning seedy.) Finally, look at the crown-shaped calyx; when the points of the crown turn slightly inward, the fruit is ripe. Pomegranates ripen from mid-summer into late fall but keep in mind they are non-climacteric, meaning they do not ripen further once they are picked. (Climacteric fruit include apples, pears, avocados, bananas, and tomatoes).
When it comes to picking, use pruning shears to do the job. If you just pull the fruit off, you are likely to tear it and decrease its shelf life. Cut the stem as close to the fruit as possible to prevent stems of fruit stored together from piercing each other. Properly detached from the tree, pomegranates' storage life parallels that of apples. They can be refrigerated for up to three months without diminishing fruit quality. If you do not have room in the fridge to store all your fruit, you can juice it as a concentrate for future use, either for drinking or as a recipe ingredient.
Where pomegranate pruning is concerned, there is really no reason for it except to remove old wood or stems that have stopped producing fruit. Generally, stems are productive for about five years. Although you can grow pomegranates as a hedge, hedging will eliminate that fruit borne on terminal growth. Pomegranates sucker prolifically and so it is easiest to let it grow into its natural bushy form, but with diligence you can train it into a single trunk specimen as well.
Avoid aggressive pruning since it will remove fruiting spurs (squat stems that grow less than 1 inch per year), occurring on two- to three-year-old stems. It is better to prune selectively, removing whole shoots or stems that are either weak or cross over more productive ones. Each deciduous fruit tree has its own pruning regime, depending on whether the fruit is borne on shoots or spurs; on pomegranate trees, the fruit it produced on both. You really need to study a tree for a number of years and see where its fruit are produced to learn how best to prune it. Nowadays, we are fortunate to have online videos to speed up this learning process.
As noted in this column on many occasions, maintenance around the tree of several inches of mulch in the form of wood chips and shredded leaves from a tree trimmer's truck should obviate the need for fertilization. However, if you do not layer mulch around your pomegranate tree, then one pound of actual nitrogen per every three feet of tree growth, applied in January prior to winter rains, is recommended. In the manner of fruit trees in general, it is best to keep a pomegranate bush/tree at a height of no more than eight feet for ease of harvest.
As for water requirement, there are reports of harvesting abundant pomegranate crops in Southern California without any tree maintenance other than occasional irrigation. One local backyard gardener reports harvesting more than 100 fruit from such a barely watered tree. The pomegranate is one of five fruit-bearing species (along with grape, fig, olive, and date) mentioned in the Bible as indigenous to the land of Israel. Thus its ability to survive drought is embedded in its DNA, as years of drought in the Middle East are as common as they are in California.
Yet although there is anecdotal success of large pomegranate crops with minimum care of the trees that bear them, it is best to ensure a regular crop by soaking established trees two to three times a month during the summer. This can be done either by installing a drip system or moving a slowly trickling hose around the canopy perimeter or drip line of the tree.
The most frequently mentioned problem with growing pomegranates is flower drop. The problem starts with the fact that the preponderance of flowers on a pomegranate tree are males with the hermaphroditic, fruit-producing flowers in the minority. The preponderance of male pomegranate flowers -- up to 70% of the flowers on a tree -- means you are going to see lots of flower drop since only flowers which turn into fruits (the hermaphrodites) stay on the plant. However, in order for a flower to produce a fruit; so where conditions for pollination are not optimal, unpollinated hermaphrodite flowers are going to drop as well.
The problem here is that the stigma (female part) on the pomegranate flower is only receptive to the male pollen for two to three days. If bee activity - pollen is carried on some of the three million hairs on a bee's body to waiting stigmas -- is curtailed due to environmental conditions, pollination and fruit development will be reduced. It is thought that adverse environmental conditions can also affect the number of hermaphrodite flowers and thus the number of fruits that develop in a given year. A summer of intense heat, for example, could reduce the number of hermaphrodite flowers that form on a tree the following spring and therefore the potential number of fruits. Even when flowers are abundant, pollination will depend on the trees' being well-hydrated and not water-stressed. That is why keeping the soil moisture level steady is important. Fluctuating soil moisture will not only affect pollination but the phenomenon of fruit splitting - whether in pomegranates, citrus, or tomatoes. In this context, it is especially important to keep pomegranate trees well-watered when their fruits are ripening because, unlike tomatoes and citrus, pomegranates have a natural tendency to split.
Pollinate your pomegranate tree by hand to enhance fruit production. Take a small artist's paintbrush and dab it on the yellow pollen grains that appear soon after pomegranate flowers open. Then transfer the pollen to stigmas of hermaphrodite flowers. On a hermaphrodite flower on a pomegranate tree, dozens of pollen-bearing anthers surround a single stigma that protrudes above the anthers.
Hand pollination is especially important where dwarf pomegranates are concerned. Some dwarf pomegranate trees -- which grow no more than a few feet tall -- appear to be completely dependent on our help when it comes to giving fruit and will only do so where hand pollination is employed. The small fruits, while edible, are not sweet and their principal attribute is ornamental since they stay on the tree for many months. Dwarf pomegranate flowers and fruits are about one-fourth to one-third the size of those on a typical pomegranate tree. Dwarf pomegranate (Punica granatum 'Nana') is sometimes pruned mercilessly into a hedge, a circumstance that quickly destroys its charm. If you decide to grow a dwarf pomegranate, just let it grow. Its flowers and fruit, which have a much-diminished opportunity to develop when it is heavily pruned, will be on full display when the plant is simply left alone.
California native of the week: California cranesbill (Geranium californium) is a semi-deciduous perennial growing a foot tall and wide. It does well in rock gardens as long as soil is kept somewhat moist. It is extremely winter hardy, flourishing in the eastern Sierras at an elevation of 8,000 feet. Starry five-petaled flowers are pink and bloom from late spring to mid-summer. I have located this plant in a Northern California native plant nursery but have not found it locally. If anyone knows of a local source for California cranesbill, please advise.