Persimmons and Parthenocarpy

persimmon tree

I have a persimmon tree purchased 9 years ago. In the past 3 years, the fruit hasn’t grown larger than a grape, changing color but not expanding in size.  The tree receives sun all day long.  Will I ever again see any full-size fruit from this tree? What am I doing wrong?

Mrs. Marty Mayer, Northridge
Persimmon is one of the most sensible fruit trees for Valley gardens.  A persimmon tree is relatively easy to maintain.  Once the tree has established its main branching structure after a few years of growth, pruning is no longer necessary. A persimmon tree’s mature size is a manageable 30 feet.  The tree is also reasonably drought tolerant and should not require more than a single weekly soaking.
The top of your tree may be getting lots of sun but, from your photo of the entire tree, it seems that the base of the trunk is in the shade.  In addition, it appears that your tree is in a low spot, at the foot of a slope, and that the bottom of the trunk, where it meets the soil, is below grade.  Thus, there could be a problem of constantly moist soil.  Soil beneath persimmon trees needs to dry out between waterings.  In fact, as a general rule, you should not water any plant until its soil is dry at a two inch depth.  I also don’t think the brick circle around your tree is a good idea since it could encourage water to collect inside it.
Here’s a good rule of thumb regarding plant health:  unless you see clear signs of disease or insect damage, plant problems are nearly always associated with what is happening below.  Typically, the soil is too wet or, on fewer occasions, too dry.  Also, if the base of a trunk is always moist — a consequence of excessive irrigation, too much shade, circling plants or ground cover that touch the tree, or mulch that covers the trunk base — you are almost sure to have problems, including root and wood rot that can cause death of the tree.
An alternative explanation for your tree’s travails is that it was planted in a root bound condition.  This means that you planted a tree that had been growing in a container too small for it, whose roots were growing in a circular pattern inside the container.  Such trees perform well for the first few years until, eventually, the tree suffers since its increased top growth is not compensated by increased root growth.  It is as though your tree, due to its circling and strangled roots, is still growing in its original nursery container.
One additional persimmon issue bears mentioning:  premature fruit drop. The reason persimmons fall from the tree before they ripen is the result of parthenocarpy, which is a fascinating botanical phenomenon.  Parthenocarpy (a word that combines “parthenos,” meaning virgin, and “karpos” meaning fruit) is the production of fruit without fertilization.  In certain persimmon varieties, parthenocarpically produced fruit is highly susceptible to dropping from the tree before it matures. In general, what we call a fruit is actually a fully developed plant ovary. The ovary is a female flower part that grows in response to pollination and fertilization of the ovum or egg.  Fertilization occurs after pollination – that is, after a male pollen grain from one flower is transferred to the female stigma of another flower – occurs.  A tube grows out from the male pollen grain into the female stigma and then continues to grow down through a filament called a style. At the base of the style, male genetic material from the pollen grain unites with female genetic material that is located there in the ovule (egg).  This mixing of male and female genetic material is known as fertilization, from which a seed is produced.
In most plants, hormone exuded by a developing seed stimulates growth of the ovary into a fruit. But in a few select plants – such as bananas, persimmons, figs, navel oranges, and Satsuma plums – fruits may grow without the benefit of seed formation. In the case of persimmons, although fruit can develop without seeds, larger crops will result and fruit will stay on the tree until ripe when pollination/fertilization and seed development occurs.  The most popular persimmon variety is  ‘Fuyu,’ whose fruit often drops when it develops parthenocarpically. To ensure a crop, plant a pollinator variety such as ‘Gailey’ next to your ‘Fuyu.’
Early fruit drop can be a self-regulating tactic that a fruit tree employs when it does not have enough resources to ripen all of its fruit. By the same token, an unsatisfactory watering regime, whether the tree is getting too little or too much water, may be implicated in early fruit drop. For this reason, mulching is recommended, a practice that lengthens irrigation intervals while keeping soil moisture at a constant level.  Excessive fertilization with nitrogen can also lead to early fruit drop since there will be a tendency toward explosive vegetative or foliar growth at the expense of fruit development.  Finally, lack of bee activity and, therefore, limited pollination and seed formation, will also contribute to premature fruit drop.
The amaranths are a curious and rewarding family of plants.  The name amaranth means everlasting (a = not, maranth = dying), which alludes to the lasting quality of their blooms.  Just the other day, on Van Nuys Boulevard in front of a car lot, I espied a rich planting of cockscomb or woolflower (Celosia argenteus var. plumosa).  The car lot cultivar had red flowers and maroon foliage.  Other garden-worthy amaranths include love-lies-bleeding (Amaranthus caudatus) and globe amaranth (Gomphrena globosa).  Amaranths are considered pseudo-cereals since, while not belonging to the grass family like wheat, oats, corn, or barley, the seeds of certain amaranth species can be used in making flour, as in the notable example of quinoa, whose flowers resemble those of cockscomb.
Tip of the Week:  If you have recently noticed a tree with and brilliant gold foliage, a round canopy, and furrowed bark, it was most likely a ‘Modesto’ ash (Fraxinus velutina ‘Modesto’).  Modestos are valued for their fall color although, over the years, they have proven to be so disease prone that they are seldom planted.  Ginkgo biloba, on the other hand, has gold, fan-shaped autumn foliage and is disease resistant as well.  Ginkgos also have a vertical growth habit so they are appropriate for use in colonnades and as sentry plants near entrances.  Ginkgos, as a bonus, are not bothered by smog and other pollutants and require little, if any, pruning.  Make sure you acquire a male ginkgo since the females produce malodorous fruit.

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