If you have a herb book published twenty years ago, the chances are that it does not even include coriander. Now it is really one of the "in" herbs, an essential ingredient of so many of the currently popular ethnic dishes. Mexican, Indonesian, Thai and Peruvian cookery are all unthinkable without coriander. All parts of the plant are used for culinary purposes, including the root, but it is the leaves that are most sought after.
Coriander is a quite short-lived annual, and with some protection can be grown for use throughout the year in Ireland. It is relatively easy to grow. Apart from being evidently quite attractive to slugs, there are no serious pest or disease problems.
The first thing of importance is to obtain the right seed for the purposes required. Given that most people want good quantities of leaves, it is one of the ‘great garden mysteries' why most seeds firms supply strains that are quite unsuited for leaf production. The most generally available strains go very quickly to flower and are more suited for seed production. Look for varieties such as ‘Cilantro', ‘Leisure', or ‘Santo'.
Coriander will do best in a deep, well-drained, fertile and humus-rich soil. They should at no time be allowed to become stressed because of lack of moisture, as this will encourage them to immediately flower - and once flower buds appear, the leaves become more serrated and loose much of their flavour. For most areas it should be possible to make a first in-situ sowing around the middle of April. Sow in shallow drills, with seeds 1cm apart, and about 20cm between drills.
To enjoy a continuous supply of fresh leaves, it will be necessary to make successional sowings every two to three weeks during the spring-early summer; from early July, sowings made every four weeks will be adequate. In the autumn the plants will be much slower going to seed, and will last until the first real frost.
An alternative method which will suit some gardeners is to sow coriander in modules or small pots, with about three seeds per cell, and germinated at 15 Celsius. It is important not to allow the cells to dry out. These may then be planted out as soon as the roots have developed sufficiently to hold the soil in the cell together.
Where a glasshouse or tunnel is available, it is possible to plant coriander from September to April inside, which will give a continuous supply of leaves October-May. Sowings during the winter should be made every six weeks or so. It is also quite possible to successfully grow coriander in pots or other containers, inside during the winter and near the kitchen door during the summer.
It is usual to harvest coriander on a cut-and-come-again basis, usually three or four times. Once flower-buds appear, it is best to cut the remaining foliage, and remove the plants.