Fennel is the name given to two closely related plants, Florence fennel, a vegetable, and herb fennel, a perennial used in salads and cooking, especially with fish. While both the vegetable and the herb can be successfully grown in a polytunnel, the herb is particularly beneficial as its flowers are attractive to a number of beneficial insects while its scent can repel some common polytunnel pests. Fennel should be sown apart from other crops, as it can have a detrimental effect on the growth of other plants. Growing it in a container, therefore, could be a good solution. It will grow well with dill, which could be sown alongside it.
Fennel should be sown in early spring indoors in modules for later transplantation, or in mid spring directly where it is to grow. It does not like to have its roots disturbed so it is best to sow in its final growing position or to use planting modules that can be placed complete into the soil, where they will protect the roots from disruption and biodegrade in place.
Bear in mind when sowing your fennel that is can grow to several feet in height in perfect conditions, so do not sow where it will block too much light for other crops. On the other hand, it can be useful as summer shade for summer salads in your polytunnel or elsewhere in your garden, or to create a partial partition or shade.
Water fennel consistently while it is establishing. Once established, your drought-tolerant herb will require little water. Make sure that the growing location is well-drained and free-draining, as the plants will not thrive with their roots sitting in waterlogged conditions. Fennel is an easy maintenance plant that will not need much attention while growing as long as it is given suitable conditions in which to grow.
The only job each year with herb fennel is to remove the dead stems at the end of each growing season, after which new stems will regrow the following spring.
Fronds of fennel can be harvested as required between spring and autumn. Not just the leaves but also the seeds can be harvested. The seeds can be used fresh during the summer months. They can also be dried for later use. Fennel, with its delicate anise flavour, is perfect with fish dishes and can be used in a wide range of different recipes.