HOW TO GROW
By David Marks
Let’s be honest, growing cauliflower successfully in the UK is slightly more difficult compared to most other vegetables. However, it’s not made any easier by the seed merchants selling so many seed varieties each aimed to mature at slightly different times of the year. More choice can create more confusion.This article simplifies the complications by concentrating on early summer and mid-autumn varieties which are the most common ones.
Temperature is a vital factor in growing cauliflower and to accurately give you seed sowing and planting out times we suggest you use our date-adjustment feature which can be foundhere. It asks you to select your home town and based on that it adjusts all the dates (sowing, planting, care, harvest etc) in this site to be as accurate as possible for your area of the UK.
TYPES OF CAULIFLOWER
There are a large number of different types of cauliflowers ranging from those that mature in early summer right through to winter maturing ones. Some varieties claim to be good for all purposes. The two most common, which we describe in this article are:
- Early Summer varieties which are sown indoors / under cover very early in the year, planted out in mid spring and mature in early summer. Normally this type of cauliflower takes about five months from sowing to the harvest stage.
- Maincrop varieties which are sown in late spring and mature in mid-autumn. These varieties are better at withstanding summer temperatures compared to other types and many are Australian varieties.
Our list of suggested varieties at the end of this article gives extensive details of each type.
Before reading this article further why not take two minutes to adjust all the dates in this website (including those below) to be more accurate for your home town (both UK and Ireland). The dates will default to the UK average if no dates are set. The settings will last for six months or more.
QUICK CALENDAR FOR GROWING CAULIFLOWER,
EARLY SUMMER CAULIFLOWER
Sow seeds indoors / under cover – February week 1
Prepare ground for planting out - February week 3 or in autumn
Harden off - March week 3
Plant outside - March week 4
Feed weekly from now on - April week 3
Begin to harvest - June week 2
MID AUTUMN CAULIFLOWER
Prepare ground - February week 3 or in autumn
Sow seed in pots - May week 3
Plant outside - June week 3
Feed weekly from now on - June week 4
Begin to harvest - October week 3
Both early summer and autumn cauliflower grow best in the following conditions:
- Do not grow them in soil which has grown cabbage, cauliflower, broccoli, kale, Brussels
sprouts, spinach or other members of the brassica family of vegetable in the past two years. See
our page on crop rotation for full details.
- The soil needs to be firm not loose. The calendar above suggests preparing the ground a few weeks before planting / sowing although the previous autumn would be even better.
- The soil acidity / alkalinity needs to be correct for cauliflowers. It needs to be neutral (a ph level of 6.5 to 7) for best results - read here for more detailed information on testing your soil and correcting it if necessary.
EARLY SUMMER CAULIFLOWERS
These types have a short growing period and need a nutrient rich soil, more so than almost all other vegetables. Ideal additions to the soil a week or two before planting outside include well-rotted organic matter or blood, fish and bone. Don't bother adding nitrogen rich fertilisers before planting, their effect is short-lasting and they are best added later on.
Cauliflowers don't appreciate the full sun in mid-summer but early summer cauliflowers will be harvested before the height of summer. So plant them in a full sun position to help them complete their full growth cycle as quickly as possible.
Mid-autumn cauliflowers have a relatively long period to produce their crop so although they still appreciate a rich soil, this is not so vital as for early summer varieties.
They will also be growing through the hottest summer months so, to avoid the worst of the heat, plant them in a position where they will be shaded from some of the mid-day sun.
To get a head start early summer cauliflower are sown indoors as seed early in the year and then transplanted outside when they are large enough. Autumn cauliflower on the other hand are best sown as seeds in mid to late spring.
EARLY SUMMER CAULIFLOWERS
Start to sow seed of early summer cauliflowers during the first week of January. Fill 8cm / 3in plastic pots with multipurpose compost and place two seeds onto the surface of the compost in each pot. Sprinkle a thin layer of finely sieved multi-purpose compost over the top and place the pots in a tray of shallow water for 15 minutes or so until the compost is damp through.
Cauliflower seed germinates best at a surprisingly high temperature of 80°F / 27°C but a more attainable temperature of 70°F / 21°C. Place the pots in a position as near to that temperature as possible, either in dark or light. The seedlings will take about four days to appear above the compost surface and it is essential at this point to place them in a position with lots of light but not direct sunlight.
The seedlings will grow best from now on if the temperature is roughly in the range 14°C /57°F to 18°C / 65°F, a good place is on a cool windowsill for early summer cauliflower.
MID AUTUMN CAULIFLOWERS
Start to sow seed of mid-autumn cauliflowers during
May week 3 . Follow the same steps as described above for early summer cauliflower. When
the seedlings germinate the pots can be paced outside in a position
protected from strong winds.
The treatment for summer and autumn cauliflower seedlings is the same, they need to grow on in good light and at the correct temperature (14°C /57°F to 18°C / 65°F). The multipurpose compost in the pot will contain all the nutrients they need for the next few weeks so only watering is required. Keep the compost moist but not water-logged.
For both types of cauliflower transplant the seedlings to the open ground when they have formed three or four true leaves, any sooner and the plants will struggle at first to grow well. If the plants are left much longer before transplanting they will also fail to establish well. As a guide, early summer cauliflower should be planted out in March week 4 and mid autumn cauliflower in June week 3
After summer cauliflower are transplanted outside it is quite likely that they will encounter a frost. All cauliflowers are semi-frost hardy and can withstand several degrees of frost but summer cauliflowers do need to behardened off prior to planting outside. Start to do this a week before planting out by gradually acclimatising them to conditions outside.
HOW TO TRANSPLANT CAULIFLOWER SEEDLINGS
First you need to get the soil conditions correct as previously described here. Immediately before transplanting firm down the soil by walking on it. Next, if it is at all dry ensure it is well watered. Use a trowel to dig a small hole about the size of the rootball and place it in the hole to exactly the same depth as it was in the pot. Firm the soil down around the rootball and then water it in again to ensure the roots and the surrounding soil are in good contact with each other.
Each plant should be at the distance recommended on the seed packet. If you don’t have the packet a distance between each plant of 45cm / 18in for early summer cauliflower and 75cm / 30in for mid autumn cauliflower is a good rule of thumb.
To provide a nitrogen rich environment, sprinkle Growmore or a similar fertiliser around the area.
To get the best formed heads of cauliflower, water and feeding are the key points much more so compared to almost all other vegetables. Cauliflowers will simply stop growing without a good supply of water and nutrients and they wont start to grow again whatever you do. So water whenever the soil begins to dry out and scatter some Growmore around them once a week.
When the cauliflower heads start to form, a few weeks before harvest, stop feeding with a nitrogen rich fertiliser and swap to a potash feed such as is given to tomatoes.
Mulching around the plants will improve water retention greatly and also provide some nutrients, just make sure that the mulch does not touch the plants.
Harvesting is something of an art, the aim being to harvest cauliflowers is just before the heads start to spread, discolour and turn slightly sour. A problem you will also encounter is that the plants mature all at the same time if left to their own devices, resulting in a deluge of cauliflower heads all at the same time. Here is our list of basic principles for harvesting cauliflowers:
- Begin to harvest when the heads are about 12cm / 4 to 5in wide. At this stage the heads would in all probability grow larger but they taste perfect and you will start the harvest early and extend the harvest period.
- Continue to harvest as required from then on. When the heads reach 15cm / 6in wide tie in some of the outer leaves over the head and hold them there with string or a rubber band. This has two effects, the first being that the leaf ribs will snap as you tie them in causing the plant to stop growing. The second is that it will keep the heads whiter for longer.
- Cut the head from the plant just below some of the leaves.
- Cauliflowers are reputed to freeze well but in our experience the texture is significantly damaged when frozen and the texture turns slightly loose and less crisp. Frozen cauliflowers are however excellent for soups.
We have two more pages about cauliflower which are listed below:
- Best performing cauliflower varieties. We stick to the common early summer and mid autumn varieties to avoid confusion.
- Pest and diseases of cauliflowers in the UK. Your number one resource for all that can go wrong with cauliflowers, how to prevent pests and diseases and available treatments.
If you have any questions or comments about growing cauliflower, pests and diseases or anything else leave them using the form below. Our experts will answer them as soon as possible.
You may also like our in depth articles on:
COMMENTS / QUESTIONS LEFT BY OUR READERS
|Date: 10 August 2018||From: John B|
|COMMENT: With regard to your comment re frozen cauliflower I find that they hold a lot
of water after cooking. If you gently squeeze them with say a potato masher in a colander you can get most of that
water out without damaging them too much. They are then perfectly fine for making cauliflower cheese.
|Date: 3 June 2017||From: Jeff|
|QUESTION: I set cauliflower seeds in modules and never have a problem germinating. The
problem I run into year after year is a serious check after potting on. The plants slowly go pale in colour eventually
turning yellow and shrivel. Sometimes they recover growing new leaves. Last year, I was lucky and plants, although
weakened, recovered to a reasonable crop.I tried less water, more water, more and less light, and different composts. The frustration is as an experienced gardener, I grow brilliant brussels sprouts, and other brassicas well most years. When my Cauliflowers grow well I
don’t know what I did right. When they fail, I dont understand exactly what went wrong. I seem to do better by not pricking out and leaving the seedlings alone until they are much bigger.Sometimes the young plants are healthy but suffer when planted out even though I’ve dug in winter, manured and much
later, checked ph, and limed. Last year was good, this year is looking like a disaster again.In late May, I set more seed of All the year round. They are just about up in modules but it may be a bit late. Soooo frustrating, but I would appreciate any advice you have which helps.
ANSWER: My suggestion would be not to pot up. Rather, sow the seeds in the final pot size, about 3 inch is what I do.Cauliflowers prefer firm soil and by potting up into fresh compost the soil may then not be compacted enough. If you start off in the final pot size the compost will naturally become slightly compacted as a result of watering.
|Date: 4 January 2017||From: Billy|
|QUESTION: When starting seedlings early in the year i use a heat bed. once germinated i hould remove from heat mat and keep in direct sunlight. I have an unheated polytunnel. So although it may get up to the temp needed for growth through the day, at night it will most certainly drop below freezing on occasions, especially in February. Can you help as what to do in this situation. Many thanks
ANSWER: You are correct, placing young seedlings in an unheated polytunnel during February and probably March as well will, in all probability kill, them.
There are two solutions to this problem. The best is probably to choose mid autumn maturing cauliflower varieties. These should be sown as seed much later in the year and this will avoid the problem of February frosts.
The second solution is to sow the seeds you have (I assume they are early summer varieties) and when the seeds have germinated position them on a cool windowsill in the house to grow on. Avoid a windowsill which gets direct sunlight because that can damage them.
Harden the plants off when the weather improves and then plant out.