When Is Fennel in Season UK?

Fennel is normally in season in the UK between July and November and is a root vegetable related to the carrot. It has a distinctive liquorice flavour that can be used raw in salads or cooked in a variety of ways – grilled fennel is smoky and sweet, and it is a staple in thousands of British soup recipes!

Fortunately, fennel is also an easy vegetable to grow and does best under full summer sunshine and with drained soil to prevent the crop from rotting or becoming overly damp. Although it can sometimes be characterised as a herb, this refers to herb fennel, a slightly different variant than we normally grow in the UK.

You should water fennel once or twice a week over the summer months and can use any general-purpose fertiliser or compost to maintain ideal soil conditions.

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How to Grow Fennel

Fennel can be grown from a seed, which you can plant earlier in the spring or start indoors in pots and transfer outside when the weather is a little warmer. If you plan to harvest your fennel in late summer, you'll need to allow a good few weeks for the plants to mature.

Each seed or seedling should be covered with around a quarter inch of soil and placed approximately ten inches apart – most gardeners will plant fennel seeds in neat rows to avoid stepping on young seedlings and allow plenty of space for the roots.

You can start sowing fennel indoors in May and sow until around late June, depending on the weather. Fennel plants grow best when the roots are left undisturbed, so it is better to start them outdoors if you are planting later in the season.

Another option is to plant fennel seeds in trays using a finer seed compost. You should break up the compost to ensure it has plenty of air and space for the roots and sow one seed per cube.

Cultivating Fennel Seedlings

Seedlings are naturally more delicate than established plants, and there are lots of ways to ensure your vegetables are nicely cultivated and grow into a tasty crop!

• If the seedlings do not get enough sunlight and the temperature is too warm, they become 'leggy' – spindly, long plants. The best option is to move the fennel to a spot where they get maximum sunlight and try to improve ventilation.
• Sowing more than one fennel seed or seedling in the same pot means one will grow and the other won’t – you can watch to see which is stronger and remove the second seeding by pinching the plant and removing it without trying to pull it out which can damage the roots of the remaining plant.

Fennel roots should not be left to dry out because the compost or soil can form a tough upper layer which prevents moisture from reaching the roots properly. If the weather is particularly hot, you might need to water infant seedlings twice a day, but every day or two is normally fine.

Before you replant seedlings outdoors, you should encourage them to harden off, which means you get the plant accustomed to colder temperatures outdoors, still in their seedling trays or pots, before planting them into the soil.

If the weather outside is very different from the original spot, you should leave your fennel for up to ten days to ensure the plants do not fail when you plant them out.

Planting Fennel Seedlings Outdoors

Most fennel plants are ready to transfer outside after four to five weeks, and you should water them well around an hour before you are prepared to plant.

Each seedling will have a small round plug at the base of the root – you need to make a hole in the soil of the same size but avoid tamping the soil down too much because the seedling needs mild conditions to grow – hard-packed soil is too tough for young roots.

You can water the seedlings again once planted but try to avoid soaking them through – the best time for this task is outside of midday sunshine.

Common Fennel Problems

Like every veggie, fennel needs a little care and attention to ensure your crop is healthy, tasty, and large. If the weather is dry, you'll need to water well, but you shouldn't overdo it and risk causing rot.

Slugs and other garden pests also love young fennel, so an organic slug treatment or trap is ideal for keeping bugs from eating your vegetables without damaging the soil or creating a risk for other wildlife or pets.

Some fennel plants experience diseases, normally because the plants are congested and planted too close together. If you leave sufficient growing room between each seedling, you can prevent this from happening.

Another great option is to hoe the soil regularly to ensure maximum light, water, and nutrients reach the roots.

Hoeing is an ongoing task for gardeners but is time well spent. The process removes the topsoil layer and helps to increase organic matter breakdown, which provides those essential nutrients to help young plants grow.

When to Harvest Fennel

The exact time your fennel is ready to harvest and eat depends on the weather and when you planted your seedlings. Still, the easiest method is to look for a bulb around seven cm in diameter – sometimes larger, depending on the variety.

If your fennel bulbs are roughly the size of a tennis ball, they are ready!

Fennel plants usually mature from July to November. Late fennel should be left in the ground if there is an early frost approaching rather than pulling up a bulb that isn't yet ready. Although fennel seedlings are delicate, an established plant is tough and will continue to grow later on into the autumn.

Gardeners recommend cutting the flower head and leaves away when you harvest because leaving the flower attached will extract moisture from the bulb and make it soft (and inedible).

You can dry out and keep the seeds for next year and store them somewhere cool and dry so they won't be exposed to dampness or heat.