How to Grow Bulb Fennel

, written by Benedict Vanheems gb flag

Florence fennel bulb growing in the garden

For those in the Northern Hemisphere the longest day of the year falls on either June 20th or 21st. The longest day of the year marks a distinct turning point in the gardener’s calendar, with summer well and truly in command and, hopefully, the first flush of harvests coming and thick and fast if not already snaffled up.

With the likes of early peas and potatoes, broad beans and carrots lifted and plucked, the first free gaps on the plot will be making an appearance round about now. Of course, no vegetable grower worth his salt needs reminding that this is the perfect signal to sow and plant once more, for crops that will be enjoyed in a few months’ time and on into fall. For me, spring is very much a mad rush to get everything up and running before the really good growing weather arrives; starting off veg from midsummer is a more relaxed affair – a far cry from the sprinter’s pace of those earlier sowings.

Fabulous Florence fennel

Perhaps the most indulgent vegetable to start off at this time of year is Florence fennel, otherwise known as finocchio or, more commonly, bulb fennel. The handsome feathery foliage of this crop is matched only by its exquisite aniseed flavour that makes a fine pairing with fish (try baking parcels of mackerel with slices of fennel and lemon for a sublime dinner). But fennel has more strings to its bow than this – pop chunks into a stew to freshen things up, or finely slice a bulb over a garden-gathered salad using a chef’s mandolin. The leaves can be used in place of herb fennel.

Bulb fennel is perhaps a slightly misleading name, as the ‘bulb’ is in fact the swollen stem base of the plant. But this is nitpicking as all you really need to know is that this is a vegetable to luxuriate in – a gourmet kitchen gardener’s treat!

The right site

One of the reasons to sow bulb fennel at midsummer is its love of sunny conditions. Hailing from the Mediterranean, it is at home in a fertile yet free-drained soil that’s lovingly basked by the warming rays of summer. While those in Mediterranean-equivalent zones can of course sow in spring, those at more northerly latitudes must bide their time to be sure of success. By midsummer the soil will have warmed up more than adequately and success will be all but assured.

Despite its sun-kissed origins, however, bulb fennel will not tolerate dry conditions. While a moisture-starved soil isn’t necessarily bad for the plant itself, it’s not great news for us; dry soil encourages plants to run to flower prematurely at the expense of those juicy bulbs. Soil that was manured for a previous crop and that’s topped with a mulch of organic matter will stand a better chance at retaining that all-important soil moisture.

To be sure of adequate moisture it is likely you’ll need to thoroughly water the ground before re-sowing with fennel. Beware the thick canopies of the potato, which exclude all but the heaviest downpours of rain. Having lifted all of your spuds the soil that’s left has a tendency to be dust-dry. Either wait for a good rainstorm to pass before sowing your fennel, or go over the ground several times with the watering can or hose to re-wet. Bulb fennel can also be grown in containers of potting compost.

Fennel in a tub)

Sowing and growing

Sowing is easy and best done direct where the bulb fennel is to grow. Sow the seeds into weed-free soil that’s been raked to a fine texture, setting seeds about 1cm (0.5in) deep. You can either station sow three or four seeds every 25-30cm (10-12in) each way, thinning to leave the strongest seedling at each position, or sow the seeds in rows before thinning in stages. It’s also possible to sow into module trays of compost before planting out, but do this promptly as the plants absolutely hate root disturbance.

Few pests will trouble your seedlings but slugs (as ever!) can be the exception. Nightly patrols to collect the slimy mollusks, the laying of beer traps or a sprinkling of pet-safe slug pellets will help to control the population.

As the stem bases begin to swell plants can be ‘earthed up’ just like potatoes by pushing loose soil up against the bases. This not only produces paler and hence more tender bulbs, it will give plants proper support and keep them from rocking back and forth in the wind.

Don’t let your bulb fennel run to seed or 'bolt'. The number one rule when growing this otherwise easy-care vegetable is that you must – and I mean must – keep the roots quenched (though never waterlogged). Water during any dry spells and apply a mulch of grass clippings or similar around the plants to lock it in.

Modern varieties are proving ever more resistant to bolting. The roll call of bolt-resistant varieties includes ‘Victoria’ with its orderly foliage, late-season ‘Cantino’ and the appropriately-named ‘Perfection’. Look out for them. In the very hottest climates heat alone can induce flowering – shading from other taller crops or temporary netting can alleviate the heat.

If one or two plants do stretch to flower, don’t despair. There’s no hurry to lift them out for the compost bin. The yellow umbels that follow not only look fantastic but are a powerful draw for all manner of beneficial insects. Fennel in full flower is a stunning sight and you could even put the case that your fennel is acting as pollinator/pest predator provider!

Enjoying the bulbs

Bulb fennel can be used at any size, with the smallest and most tender bulbs best for use raw in salads. Warm bulbs taken during the heat of the day can be freshened up by submerging thin slices in a bowl of iced water for up to an hour. They’ll soon regain their rigidity and full flavor. Cut the bulbs an inch above ground level and allow the stump to re-sprout (a trick that also works for cabbages). The bonus take of feathery shoots is both delicious and delicate.

However you use your bulb fennel you’ll be pleased you made the sowing. Just think, within just two months of reading this you could be enjoying the luxury of your own bulbs. It’s a tempting thought.

By Benedict Vanheems.

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Show Comments


".since becoming a lover during a stay in Italy, I´ve been trying to grow these in Iceland with difficulties because of sudden frost in spring.I´ll try this tardy sowing next year.thanks for the tip of summer sowing"
Patricia on Sunday 8 July 2012
"I've grown fennel off and on for years, but never knew what to do with it. Thank you for the excellent information on how to grow and use fennel."
Lon on Sunday 8 July 2012
"its also delicious as a salad.thinly slice fennel in a bowl with orange segments with membrane removed, olive oil, salt and pepper. Or roast - slice in four pieces with the base intact, rub with olive oil and roast with other veges."
chris on Sunday 22 July 2012
"Fennel makes the most wonderful addition to chicken soup. it is especially good if you reserves some of the tops to sprinkle in the bowl with dill when serving."
Fran on Sunday 30 September 2012
"I live in the okanagan B.C. can I grow fennel here?"
Grace on Sunday 10 February 2013
"Hello. Yes, fennel should grow in Okanagan. But I notice it is quite a dry part of BC, so be sure to keep a check on soil moisture levels. Water plants as necessary to keep them growing away strongly. Good luck with it!"
Benedict Vanheems on Sunday 10 February 2013
"I have fennel growing in my herb bed but am not sure if it is a bulb fennel or just the herb. How do I tell please? "
Ellen Wilson on Saturday 8 June 2013
"Hi Ellen. If it is bulb fennel it will fairly quickly start to swell at the base of the plant - the start of the 'bulb' forming. If it's herb fennel then the plant will grow much taller, quicker. Give it a few weeks and you'll easily be able to tell the difference."
Benedict Vanheems on Monday 10 June 2013
"I make fennel slaw with cabbage, carrots, white turnips, fresh dill, rice wine vinegar and a litlle mayo. Ot try fennel, cukes, cabbage.....just use what you have that is crunchy! Fennel seeds or coriander seeds are also good seasonings..."
Ruth Apter on Sunday 7 July 2013
"all my fennel is going to seed at the moment. Probably didn't water enough during the hot and dry few weeks we've just had... I wonder, is there any point in cutting it 1" above ground level, as you suggest, in the hope of a secondary crop rather than just letting it flower?"
Frankie Martin on Monday 29 July 2013
"Hi Frankie. You could give that a go, certainly, but I'd be inclined to let them flower and pull in the beneficial insects."
Benedict Vanheems on Thursday 8 August 2013
"I buy bulbing fennel seed and it almost always wants to bolt....not enough watering??? Also, it's perennial???If I cut those stalks off, will they return the following yr with the possibility of bulbs(if I H20 more.)??"
Rosann on Monday 12 August 2013
"Hi Rosann. I'm afraid I'm not entirely sure if your fennel will bounce back next year. As it grows reasonably quickly I'd be inclined just to start afresh next year by sowing a new crop. Keep the plants well watered as they grow and, fingers crossed, you'll finally get some bulbs."
Benedict Vanheems on Thursday 15 August 2013
"Hi. I planted fennel for the first time in early June and while its looked great bulbs haven't really swelled. They are there but flat! I keep waiting but now some is bolting ( not enough watering recently in my absence ). Will they grow eventually or should I try what's there now and leave the rest for insects? Amanda London "
Amanda on Monday 2 September 2013
"Hi Amanda. I'd leave those that have started to bolt to do so. Hopefully the other plants will continue to swell - keep them well watered if conditions are dry where you are."
Benedict Vanheems on Tuesday 10 September 2013
"Hi. I tried 2 bulb fennel plants this spring and they are still in the ground. I live in the Fraser Valley of BC. Can you give me instructions on when to harvest and can I cut them down and leave over the winter for next year?"
Karen on Sunday 27 October 2013
"is it possible for me to grow this in a long pot on my kitchen window sill? it will definitely get that 6 hours of direct sunlight daily, but I am afraid it wont grow as well if its not outside. any tips?"
Devin on Monday 11 November 2013
"My wife dosn't like onions. So as a person of Italian decent one of my favorite quick meals is, sausage peppers and onions. Well that no longer flies in our house. Now we do fennel, peppers and sausage. the fennel complements the sausage since there is fennel seed in sausage and the texture of the fennel is very much like onions. When I make it I sneak a few onion slices in and she doesn't suspect a thing."
Marty on Friday 22 November 2013
"I live in the Philippines, a tropical country. Can I grow some fennel here as well? Thanks"
Miguel Angelo Oppus on Wednesday 12 March 2014
"Hi Miguel. I can't say I know the answer to this one for sure, but as Florence/bulb fennel prefers warmer weather and plenty of moisture, you may well have success in the Philippines - I'd say give it a try! Let us know how you get on."
Benedict Vanheems on Wednesday 12 March 2014
"I am in Oklahoma and the summers here can get very hot and dry. what do you think can I grow fennel? I have seed Zefe Fino looks like the bulb type. Plz advise."
Michael on Friday 20 June 2014
"Hi Michael. You should be fine growing fennel where you are - just make sure to keep plants well watered so that they are not under any water stress."
Benedict Vanheems on Monday 23 June 2014
"Hi I want to dig up a fennel plant an regrow it in a different area can I? An how do I do it?"
Missy spartin on Thursday 11 September 2014
"Hi Missy spartin. As long as you take great care to lift up as much of the root system undisturbed as possible, you should be fine."
Benedict Vanheems on Thursday 11 September 2014
"Hello Benedict - What a wonderful informative blog. I live in Whanganui New Zealand with a very temperate climate so I'm choosing early summer planting. What do you think? I have so far had no success with the Florence fennel bulb. I have been sent the Caillard's Fenouil Fino Race Zefa bulb seeds from Europe and hope to grow them for seeds and bulbs. I do wonder however, if the prolific roadside fennel (with seeds for cooking) will contaminate the new European bulb seeds if the bees keep up their good work?. At this time of the year we pay close to $US10.00 for one mature bulb from the retailers. Thank you Alyson "
Aly Hamilton on Thursday 4 August 2016
"Hi Alyson. If you are sowing fresh seed then they will go on to produce bulbs. The risk of cross contamination only happens if you were intending to let your plants flower to collect seed for the following year. If not, then you've nothing to worry about - the plants will produce their bulbs and you can lift and enjoy them when they're ready. $10 for a mature bulb sounds extortionate - good idea to grow your own! Hope it goes well - let me know how you get on."
Ben Vanheems on Friday 5 August 2016
"I was introduced to fennel bulbs two years ago and I am now addicted. One tip if you want to extend the growth. When you cut the bulb , cut at ground level leaving the root system in your garden. You will notice side shoots springing up in a few weeks. Up to six per root. , you will never get a real bulb , but wait a few weeks, and you end up with light extended bulbs. I use them sliced up in stews or under neath roasts. Has any one else tried this, two crops from one plant."
Lynette winters on Monday 17 October 2016
"Wow Lynette, that's a brilliant idea! I haven't tried this yet, but will definitely give it a go next time I grow fennel. "
Ben Vanheems on Monday 17 October 2016
"Can Fennel be grown as a perenial in Edmonton,Canada? we have minus 30 celcius winters and a friend has a huge plant , they tell me its a perenial and gave me some seeds they harvest every year, the plant is about 5 ft tall and did not see any bulbs. am going to try them. e=mail me at"
Antonette Lobo on Sunday 7 May 2017
"Can fennel be grown as a perrenial in Edmonton,Canada? our winters are really cold and a friend harvests seeds from his plant each year. Its about 6ft tall."
Antonette Lobo on Sunday 7 May 2017
"I cannot comment on this as we do not have such cold temp. Light frosts 3-6 times over winter"
Lynette on Sunday 7 May 2017
"Hi Antonette. There are two types of fennel: bulb, or Florence fennel, and also herb fennel. Florence fennel is grown as an annual - sown in the spring/early summer and harvested before it gets cold in the fall. Herb fennel is probably the type you have, given that it has grown to 6ft tall. This type is indeed a perennial - the stems grow tall during the growing season then die back to the ground by winter. New shoots follow from the base in spring. It is a hardy plant that should survive temperatures down to about -34 Celsius, so you should be able to grow it in the ground where you are in Edmonton. That said, it may be worth saving a few of the seeds every summer, just in case it is killed by the cold. These can then be sown in spring, so you'd cultivate the plant as an annual. But it should survive where you are."
Ben Vanheems on Monday 8 May 2017
"Thank you very much Ben, will try to grow this type and hope we get some results."
Antonette Lobo on Monday 8 May 2017
"Hi, I haven't read all the posts, but if your fennel does go to flower or for some strange reason you don't need it all or use it. Please leave it out. Swallowtail butterflies need fennel to host their caterpillars on. It's one of the few plants that can host swallowtails and with swallowtails declining rapidly. It would be nice to lend a helping hand. Remember**** without pollinators in the wildlife chain. Our gardens and farms would begin disappearing very the years. Thank you"
Maryann Farrell on Tuesday 15 August 2017
"Thanks for sharing that Maryann. I hadn't realised swallowtails depended on fennel so much. I'd also say it's definitely worth growing herb fennel too - it's very graceful in flower and as well as butterflies the hoverflies love it."
Ben Vanheems on Wednesday 16 August 2017
"Hello, I love eating raw fennel and this year bought some seedlings for the first time. Probably in wrong time, we may get some slight frost during the winter months. Living in S.A. in Adelaide Hills. Is there any point to grow them in the winter in pots in my small glasshouse and replant them in spring to the garden? And I was always wondering can you eat those "wild" fennel along the roads? Thank you for your answer. Ludmila S.A. Adelaide"
ludmila Bohacik on Friday 13 July 2018
"Hi Ludmila. My concern about over-wintering your fennel is that it will almost immediately bolt (flower and run to seed) as soon as the weather warms up again in spring, so you won't get much of a crop. But you could certainly give it a go. I'm not familiar with wild fennel in S.A., but here in the UK I have in the past eaten bits of semi-wild fennel with no ill effects. But you really have to be absolutely certain it is fennel and not some other similar-looking plant."
Ben Vanheems on Monday 16 July 2018
"Hi. Grew bulb fennel for the first time last with great success - beginners luck. Here on the North Norfolk coast the soil doesn’t get above 12C until mid June - about a month later than anywhere to the west, followed by intense heat and dry. Damping off is a problem. I recommend fleece covering to warm the bed and keep it in place over plants with constant misting. Seems to do the trick. Actually am still cutting regrowth for salads in January after several hard frosts without suffering any damage. Amazing. "
Mark on Friday 29 January 2021
"Hi Mark. That is amazing! I had a few fennel left in the ground but they are well and truly clobbered by the cold and, perhaps more of an influence, the extreme wet. I think the soil is a little sandier in your neck of the woods, which probably helps too?"
Ben Vanheems on Sunday 31 January 2021
"Have grown bulb fennel for years here in the Western Cape, South Africa. It grows even in heavy clay soils. We never sow any as it sows itself and comes up everywhere. Replant when young because of the tap root if you want it in a specific bed but the plants that come up on their own are just as good. Cutting down at ground level (approx) is perfect as the plant makes new bulbs, though smaller. HUGE insect draw card and flowers for many many months, so incredibly valuable microhabitat. The seeds are also delicious. I cook it finely sliced with lots of onion, tomatoe, garlic, chorizzo, (chilli), serve with pasta, parmesan and red wine. Steamed sliced fennel freezes well for cooking up when there are no bulbs. One of the easiest, most delicious and all round 'good for the environment' vegetables!"
Erika on Saturday 29 May 2021
"Wow - your fennel grows nice and easily Erika. I often have trouble getting it to germinate properly. I'll be trying your method for cooking it - it's a cracking vegetable!"
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