Where’s my fruit?
We think flowers are just there to look pretty, but for the plant, they are how they reproduce themselves. If you've got flowers but no fruit on your fruit trees, chances are you're missing a vital piece of the puzzle: pollination.
Most flowers contain male and female parts, which are usually surrounded by petals. The male parts – called stamens – produce pollen. Pollen is usually seen as yellow grains held on anthers.
The female part of the flower is called the pistil and includes the stigma, which accepts pollen. The stigma sits at the top of an elongated structure called a style, which takes pollen to the flower’s ovary. When the pollen reaches the ovary, fertilisation takes place so that each flower can form seeds and fruit.
Generally bees and other insects transfer pollen from a flower’s anther to its stigma, but sometimes pollen is spread by wind, small animals and birds, or even by vibration (known as buzz pollination).
Gardeners are mainly concerned about the world of pollination when they want to grow a productive garden and produce fruit. Without pollination, fruiting plants simply won’t bear any fruit.
The ingredients for pollination (and fruiting) are pollen, a receptive stigma and a pollinating insect (usually a bee), which carries pollen to the stigma. While it sounds straightforward, complications can occur as some flowers are not pollinated by their own pollen.
They need pollen from another flower, often from another plant and even from a different variety. This is known as cross-pollination, and is why bees (and other insects), which fly from flower to flower, are so important. They carry pollen so the cross-pollination occurs. Without cross-pollination, crops may be poor or non-existent, so a really important question to ask when buying any fruiting plant is: “Does it need cross-pollination?”
Most deciduous fruit trees, but especially apples, some pears, some apricots, most sweet cherries, some peaches and many plums, need cross-pollination for good fruiting. This means planting two varieties that flower at the same time, or buying a tree that has been grafted with two varieties - the main fruiting variety and its preferred pollinator. Always carefully identify the pollinator branch on a multi-grafted plant so it isn’t accidentally pruned off!
With the pollinator trees in place, all that’s needed is flowers and bees. Flowers will come when the tree becomes mature. This may take seven to 10 years with trees raised from seed, but today most fruit trees are grafted, which means fruit is produced within one to three years from planting.
For tips on how to encourage pollinating insects to visit your garden, see our tips on attracting native bees. Information on suitable pollinators for each fruit variety is usually included on the plant label. You can also ask one of Flower Power's friendly horticulturalists, available at all 10 Flower Power stores.
The most commonly grown evergreen backyard fruit trees, citrus (including oranges, lemons and mandarins), don’t need cross-pollination - however, cross-pollination is important for many other evergreen fruit trees including avocado, mango and olive. Having a pollinator variety, either grafted or planted nearby, dramatically improves pollination and increases fruit production for these trees.
This is also the case with fruiting plants that are normally self-fertile (which means they don’t need cross-pollination). Blueberries, for example, have better crops if there’s another blueberry that flowers at the same time planted nearby.
Even more complicated
While most flowers contain both male and female parts in each blossom, there are some plants that have separate male and female flowers on separate plants. This means that both male and female plants are necessary for the female to form fruit.
It isn’t necessary to have equal numbers of male and female plants – usually one male plant is enough to pollinate up to eight or nine females. Examples of productive plants with separate male and female blooms are pepperbush (Tasmannia lanceolata), a native bush with peppercorn-like fruit, and kiwifruit. As kiwifruit are sprawling vines, look for female plants grafted with a male branch to reduce the space needed to grow these delicious fruits in the backyard.