The bay tree typically used in container growing is the bay laurel, referred to scientifically as Laurus nobilis. Bay laurel trees can be grown as standard, dignified ornamentals, or their flexible stems can be worked in a variety of fashions and heads can be shaped as desired. This tree, whose leaves are used to flavour dishes, has significance in mythology, religion and history. The strong smell of bay leaves protects the tree from many pests, but it can experience occasional problems.
Bay trees, which are native to the Mediterranean shores, can tolerate a degree of dryness. However, bay trees should be watered regularly, especially during summer months if the plant is kept in a pot. Bay trees moved indoors to a sheltered location during winter months require very little watering. Inadequate water during the summer can cause leaves to turn brown. Fertiliser should be used with caution, as too much fertiliser will encourage the plant to quickly outgrow the container and appear imbalanced. Slow-release balanced fertiliser can be applied at the beginning of the growing season in March. A balanced liquid fertiliser can be diluted and applied to pot-grown plants every few weeks.
The bay tree is only hardy throughout the UK. The tree can only tolerate temperatures as low as -6.67 degrees Celsius (20 degrees Fahrenheit). Potted trees are even less tolerant, as their roots become chilled quickly. So, the bay tree must be brought indoors in cold climates in order to survive. The ideal wintertime temperatures for the bay tree are around 10 degrees C (50 degrees Fahrenheit) at night and only about 5 degrees Celsius (10 degrees Fahrenheit) warmer during the daytime. The tree requires no fertiliser during the winter and less water than during the active growing season, but plants should be monitored to ensure that they do not dry out.
Shaping and pruning
Standard bay tree protocol calls for a total height, including the pot, of about 1.8 m (6 feet); the trunk should be about 105 cm (42 inches) long before it begins to branch. The head of the plant should be approximately proportionate to the pot. There are generally two types of pruning for this tree. The first type is top pruning, which can be done incrementally throughout the winter as bay leaves are used for cooking or potpourri. This pruning should remove only a few inches from the top and be completed by late March. Root pruning is also necessary to avoid the need for repotting, and it prevents the tree from becoming root-bound. Before the tree begins its spring growth flush, remove the plant and gently tease about 5 to 7.5 cm (2 or 3 inches) from the bottom and sides of the mass. Cleanly trim exposed roots even with the soil. Then repot the tree, putting new potting compost on the bottom of the pot and in the gap around the edges.
As an aromatic, bay trees have relatively few insect pests. If the bay is attacked by scales, wash it in warm, soapy water or treat it with a horticultural oil. Scales secrete a sugary substance that attract a grey mould. The eastern tiger swallowtail butterfly may also feed on the bay.