Flowering and pollination plays a critical role in fruit formation. To me there are few things more beautiful than a fruit tree in full bloom in the early spring. That beauty is more than just appearance, it's also important to a bountiful harvest.
There are some things the successful home orchardist needs to know though. Depending on where you live the weather can play a role in successful flowering. Here is Southern Indiana a late frost is always a concern, especially if it follows an early warm spell. Proper pollination is essential to a successful harvest.
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Fruit trees, especially peaches and plums it seems, can begin flowering earlier than they should. A late winter or early spring warm spell can cause your trees to break dormancy too soon. If the warm spell is followed by a hard freeze, it can wipe out, or at least reduce, an entire year's crop before it can even start.
It surprises me over and over how resistant to a light frost or freeze a fruit tree in full bloom can be. Temperatures above 28°f don't seem to do much harm, but the longer it's cold, the more damage can be done.
Commercial Orchards use smudge pots spaced out among the trees at regular intervals. These smudge pots burn kerosene or diesel fuel to generate heat in the orchards, and help to prevent damage for a relatively short period of time, like overnight. Using smudge pots probably isn't a reasonable option for most home orchards. So, what is the small scale home orchardist to do?
Small trees can be covered with a sheet or blanket the night before to prevent frost formation and hold in absorbed heat, but you have to take care that you don't do more damage (knock blossoms off) putting on and taking off the coverings than the frost would have done. Unless you are in for a hard freeze (below about 28°f) use your own judgment. The larger your trees get, the less likely it is that you will be able to cover them.
In many cases with larger and more mature trees, all you can do is let nature take it's course. The good news is the larger a tree is, the more mass it has, and the more heat it can retain from a sunny day before the freeze. This means on a cold calm night, a large tree may give off enough retained heat to keep the air in the crown of the tree warm enough to avoid damage. Only the outermost branches may suffer damage. If there's a breeze though, all bets are off.
Some fruit trees require a companion pollinator tree, since they are not self fruitful. This means that the tree cannot pollinate itself or another tree of the same variety. For example, sweet cherry trees almost always require a second variety of sweet cherry tree for them to be fruitful. There have been a few self fruitful sweet cherry trees developed recently, but most are not. Sour (pie) cherry varieties on the other hand rarely require a companion pollinator.
Most reputable mail order companies will tell you not only if you need a pollinator, but will generally recommend the best variety to chose for that purpose. If buying form a local nursery or big box store, be sure to read the tags on the tree. Pollination requirements will usually be listed on the planting and care instructions.
Most fruit trees do not absolutely require another tree for pollination in order to bear fruit. However, using a companion pollinator will almost certainly increase pollination and allow your trees to produce MORE fruit. I don't recommend ever planting just one fruit tree of any variety. Always plant at least two of any kind of fruit tree if room allows.
When people think of flower pollination they usually think of honey bees, but the most important pollinators of fruit orchards in the U.S. are bumble bees and orchard mason bees. Fruit trees generally bloom when it's still too cool for honey bees to be very active.
Bumble bees and orchard mason bees are active earlier in the year in cooler weather than honey bees. There are also many other species of small native bees that help to pollinate your fruit trees.
A NOTE ON INSECTICIDES:
Never spray insecticides on your fruit trees when they are in bloom. Sevin and other insecticides are EXTREMELY TOXIC to bees - more so even than it is to most pest insects.
Kill off your local bee population and you can forget about having a successful orchard (or a garden, or berries...).
Although I don't consider myself as an intentional "organic" gardener, I do believe that you should limit the use of insecticides to just bare necessity. The main reason for this belief is the severe damage that they do to bee populations, and the devastating impact of losing these valuable pollinators.
With no pollination there can be no fruit formation. Most fruit trees (apples, pears, peaches, plums, cherries, etc) are all close relatives to the rose family, as are blackberries, raspberries and strawberries).
When your fruit trees bloom, you will note that the blossoms are very similar in appearance and form to a wild rose blossom. They all have a remarkably similar appearance - 5 round petals surrounding the stamens & pistil.
Stamens are the male organs of a flower and produce pollen. There can be as many as 30 stamens in a blossom. Stamens are the small filaments that protrude from the center of the blossom. Pollen is produced at the tips of the stamens.
The Pistil is the female organ of the flower. There is only one pistil in a blossom. It is found in the center of the stamens, and is noticeably thicker than the stamens. The pistil is essentially a tube that receives the pollen, and carries it down to it's base where the ovary is located.
The ovary will develop into the fruit. The fruit form at the base of the flower. As the fruit grows, it will split the dried husk of the blossom which will eventually fall off.
Proper pollination is essential to fruit development in your home orchard. Take steps to assure success by protecting trees from late frosts and freezes, and selecting the proper "companion" pollinator for your trees. Encourage native bees to take up residence in or near your orchard and protecting them from pesticides. A little advanced planning and preparation can go a long way.
Home Orchard Topics:
Orchard Mason Bees
The Home Orchard's Best (Unknown) Friend:
Most people know bumble bees, but orchard mason bees are not very well know. These small gentle native bees come out early, gathering pollen and nectar, build their nests, lay their eggs, and die off before the heat of summer. Each spring produces a new generation of bees.
They are one of the most efficient and effective pollinators of your home fruit orchard.
They are quite small, about 1/4 to 1/2 inch long (about half the length of a Honey Bee) and considerably thinner too. There are several things that you can do to promote them in your orchard. Here is a link for more information: