Genetics and the part they play in compatability is a major factor in producing a good crop of berries. The following should be considered, particularly if you have tried to improve the cultivation and environmental factors.

Lack of a pollination partner: Many trees and shrubs are naturally dioecious (male and female flowers produced on separate plants), so you need to make sure you grow both male and female plants to pollinate each other. In the nursery or garden centre, plants of different sexes are often stated on the labels, for example:

Ilex aquifolium ‘Madame Briot’ female
Ilex aquifolium ‘Silver Queen’ male
Skimmia japonica ‘Rubella’ male
Skimmia japonica ‘Veitchii’ female

Some female cultivars of Ilex (holly) may produce a few berries even when isolated but, for regular and full berrying, a male cultivar is required nearby. Unfortunately some plant names can be misleading; the holly‘Golden King’ is actually female and 'Silver Queen' is male! Check in the RHS Plant Finder to be sure.

Self-incompatibility: Euonymus europaeus and its named clones have variable self-incompatibility (are partially or fully self-sterile) and, therefore, one plant on its own may often not produce berries. To be sure of obtaining berries, it is necessary to plant two plants reasonably close together so that there can be cross pollination. However, it is also necessary to plant separate clones (the genetically identical off-spring of a single parent, produced by vegetative propagation).

Sterility: Some plants such as Rosa moyesii and Rosa moyesii ‘Geranium’ (which is more compact and larger-fruited) are often sterile when raised from seed so will not produce their usual crop of hips. These plants should always be propagated by budding or grafting onto a rootstock.

Seed-raised plants: If trees or shrubs have been grown from seed rather than bought from a nursery, their fruiting potential may vary considerably from named cultivars, which are propagated vegetatively from selected plants with a known capacity for good berry production. Where seed-raised plants give a poor performance, they are best disposed of, and stock obtained that has been propagated in a nursery by budding, grafting or from cuttings that will have the good flowering and fruiting qualities of their selected parent plant. Remember also that seed-raised trees and shrubs have a juvenile period that may last several years, during which they grow often vigorously but only settle down to their productive (i.e. flowering and berrying) phase later. Plants propagated by cuttings or grafting tend to flower more quickly.

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