Pollination of pears
With pears, there are diploids and triploids, exactly as with apples.
But there are also tetraploid pears and these have the ability to pollinate themselves so that a single tetraploid pear tree can be grown successfully. The choice of variety is extremely limited, however, and Improved Fertility is usually the only one to be found in nurseries.
A few pears are incompatible with each other. None in this group will cross-pollinate with any of the others: Fondante d’Autonine, Laxton’s Progress, Louise Bonne of Jersey, Precoce de Trevoux, Seckle and Williams’ Bon Chretien.
Beurre d’Amanlis will fertilize Conference, in spite of being a triploid, but not vice versa. The three varieties Beurre Bedford, Bristol Cross and Marguerite Marillat will not pollinate others.
Aiding natural pollination
Inadequate pollination can be the cause of malformed fruits, often noticeable in early greenhouse tomatoes and straw-berries under cloches or plastic tunnels which have been left unventilated at blossom time. It can also be responsible for the currant trouble known as run-off, when some or all the fruit on a strig fail to develop.
As we have seen, in a few cases it is essential to take matters into your own hands and do the pollinating yourself, but largely you should rely on insects to do the work for you. Provide wind-breaks, if necessary, to make early spring conditions more genial for pollinating insects and never spray the fruit trees, bushes or any other crop with insecticide while the flowers are out.
Wild bees are valuable friends. They will not harm you and are one of the major insects that pollinate fruit and vegetable crops.
You can lure bees to your garden by planting attractive plants such as thyme and spring-flowering shrubs— cotoneaster, broom, pyracantha, flowering currant, rosemary and creeping willow (Salix repens) are all good for this.
Some gardeners place bouquets of flowers in jam jars in their frames to attract bees when melons are in flower. Others entice them by spraying their melon foliage with a honey and water solution.