Perhaps you expected that this article was going to be as exciting as Adam and Eve in the garden of Eden. Well, maybe not as exciting, but surely as important! It will address the fine points of how we’ll get from blossom to fruit crop. Numerous factors can make the process go awry. Your understanding of the pollination process can help achieve a bountiful harvest. Two important points to remember that apply to all edible fruit plants:
- Bees and other pollinating insects rarely carry pollen to plants at a great distance. Hence it is highly beneficial to plant tree fruit varieties within 100 feet or less of each other. Nuts and berry bushes do best when within 50 feet of a pollen source.
- Bee flight is severely curtailed below 65°F. This can result in limited to no pollination and a reduced fruit crop.
Does Your Fruit Tree Need a Partner?
The production of flower buds alone is not enough to insure production of a successful fruit crop. It is really only the first step. Once the bloom is visible, the critical processes of pollination and fertilization are starting to take place. Pollination is the transfer of pollen from the male parts of a flower blossom to the female parts. To complicate matters, a number of different fruit varieties have pollen that is not compatible with itself, the variety that is providing the pollen. This is the case with apple, pear, most sweet cherry, Japanese plum, non-astringent oriental persimmon, blueberry, and kiwifruit.
For example, most apple varieties need to be pollinated with pollen from a different apple variety. This condition is known as being self-unfruitful. A Red Delicious apple will not successfully produce much fruit if pollinated by another Red Delicious. However, if that same Red Delicious blossom receives pollen from a McIntosh bloom, it will most likely develop a nice crop of fruit (other normal conditions cooperating.) This process of sharing pollen between varieties is known as cross-pollination.
Sweet cherry, will challenge you a bit more. Not only is it self-unfruitful; there is also some cross-incompatibility between certain related sweet cherry varieties. That is, not all varieties of sweet cherries will pollinate all other varieties. So you must choose from varieties of sufficient genetic variation — one from group A and one from group B, as it be. Most nurseries offer cross-pollination charts in their catalogs indicating appropriate choices. If you are extremely short on garden space, two varieties of sweet cherry, Lapins and Stella, are self-fertile and do not require cross-pollination by another variety.
Time to Tango — or Bloom
In addition to taking cross-pollination needs into account, it is equally important to pay attention to when the various varieties bloom. The time that the receiving bloom of one variety is open needs to coincide closely with the time that the pollinating variety is also blooming. Otherwise, proper pollen transfer and fertilization will not take place. Fertilization occurs when the male and female genetic material are united to form an embryo which can then develop into the fruit.
Bloom is typically thought of as early, mid-season, or late blooming. (Note: this does not necessarily correlate with the maturity season of the fruit.) It is best to choose two or more varieties from within the same group, but it is possible to choose one variety from the early group and one from the middle blooming group as their bloom time will often overlap somewhat. If you choose one variety from the early group and one from the late however, their bloom times will likely be too far apart to pollinate each other well.
Some fruit do not require cross-pollination and are termed self-fruitful — notably apricot, European plum, tart cherry, peach & nectarine, fig, quince, astringent persimmon, blackberry, currant, gooseberry, raspberry, strawberry, and perfect flowered muscadine.
To Each His Own
Beyond the general considerations of pollination some fruit have a few individual quirks.
- Apple — There is a small percentage of apple varieties that, due to peculiarities of nature, have a triploid number of chromosomes. As a result, their pollen is sterile. Although they can be successfully pollinated by other varieties, they cannot themselves serve as reliable pollen sources for other varieties. If you do want the fruit from one of the varieties listed below, be sure that your fruit planting is made up of at least three apple varieties, including those with viable pollen.
Triploid varieties include Arkansas Black, Baldwin, Belle de Boskoop, Bramley Seedling, Gravenstein, Jonagold, Mutsu, R.I. Greening, Sir Prize, Spigold, Stayman Winesap, Summer Rambo, and Winesap.
- Kiwifruit — Unlike most other cultivated fruit, kiwifruit have some plants that bear male flowers and other plants that bear female flowers. Although flowers on either type of plant will have both male and female reproductive parts, only one reproductive structure is functional in each case. Normally the female flower is slightly larger in size than the male flower, making it possible to visually distinguish between the two. It is best to have a male flowering kiwifruit vine within twenty feet, and definitely no further than thirty five feet, away from any given female vine. As a rule of thumb, a ratio of planting one male per six female vines is recommended. Of course if you only want one female, you will still need a male plant too.
- Muscadine grape — While bunch grapes are self-fertile, this is not the case with all muscadines. Many of the newer varieties are self-fertile; but many of the old varieties are pistillate, or female. Consequently, they need to be planted together with a pollinating variety. For the best pollination, plant at least two self-fertile varieties within fifty feet of any pistillate variety. Among the popular pistillate varieties are Black Beauty, Fry, Sweet Jenny, Sugargate, Summit, and Supreme.
- Peach — A few varieties of Hale parentage break the norm. Early Hale, Halehaven, and J.H. Hale are self-unfruitful; neither pollinating each other nor able to be pollinated by Elberta.
Regardless of the individual quirks, there are hundreds of fruit varieties, making it possible to find a partner for just about anything you might want to grow.
©2013. Adapted from the Backyard Berry Book: A hands-on guide to growing berries, brambles, and vine fruit in the home garden and the Backyard Orchardist: A complete guide to growing fruit trees in the home garden by Stella Otto.