Qualification - Certificate in Vegetable Growing and Production

Course CodeVHT044
Fee CodeCT
Duration (approx)600 hours

Become a Vegetable Producer

Understand more about vegetable production, crops and organics with this certificate level qualification.

The course provides a thorough grounding in all aspects of growing vegetables from sowing seeds to selling produce to the marketplace.

Work through the course at your own pace and learn more about vegetable growing and production. 



Core ModulesThese modules provide foundation knowledge for the Qualification - Certificate in Vegetable Growing and Production.
 Commercial Vegetable Production BHT222
 Agronomy III (Root Crops) BAG310
 Horticultural Marketing BHT304
 Mushroom Production BHT310
Elective ModulesIn addition to the core modules, students study any 3 of the following 7 modules.
 Commercial Organic Vegetable Growing VHT241
 Culinary Herbs VHT242
 Microbiology BSC209
 Agronomy BAG306
 Agronomy IV - Arable Farming Legumes BAG311
 Bush Tucker Plants: Growing and Using BHT328
 Soil Management (Crops) BHT303

Note that each module in the Qualification - Certificate in Vegetable Growing and Production is a short course in its own right, and may be studied separately.

How Do You Grow Onions

Onions are easy to grow and can be planted in the same spot each year. They can also be grown throughout the year making them perfect for filling in empty spaces in the vegetable patch.

Onions all belong to the Allium genus and the Alliaceae plant family. This genus includes those considered to be vegetables such as field onions, spring onions and shallots, as well as others which are more usually recognised as herbs, like garlic and chives. They all have variations of the same oniony taste, some being mild and some strong, and they all staples in a wide range of culinary dishes.   

Which Ones to Grow

The growth of onions is influenced by daytime temperatures and day lengths. Some need about 10 to 12 hours of daylight each day to reach maturity. These are known as short day types. Others need more like 14 to 16 hours a day and are classed as long day onions. There are some intermediate types in the middle which need 12 to 14 hours of daylight. If you plan on growing onions to sell at market then you'll need to bear this in mind and choose ones that will be ready to crop when you need them. For personal use, it's not so important but don't be surprised if your onions show little sign of growth if you select the wrong type at the wrong time of year. We would recommend consulting a local nursery or garden centre to find out which types do well in your area, and take things from there. There's no harm experimenting either, especially if you fancy something more out of the ordinary.

For milder onions think of spring onions, shallots, scallions, leeks, red onions and many of the larger sized onions. For pungent ones, which are more suited to cooking, you are best considering brown onions (also known as yellow onions in the United States) and white onions. Pickling onions also have a sharper taste which is why they lend themselves so well to preserving. As a general rule, those with thicker outer skins like brown onions will last longer in storage.


When to Sow

When growing from seed, the best time to sow will depend on the local conditions. Because onions are cool season crops, in warmer countries and regions onions are mostly planted in autumn after the summer heat has faded. In temperate regions onions can be planted as a main crop in spring or autumn.  Those planted in spring will be ready to harvest in autumn. Those planted in autumn will take longer to reach maturity and will be ready a month or so before spring sown ones. Spring onions, shallots and scallions are usually sown in late spring to early summer for harvesting the following spring. If you stagger your plantings by a month or two, you can probably have onions throughout the year. In cooler regions you'll need to look for non-bolting varieties because very cold temperatures will encourage the plants to produce flowers and seeds at the expense of bulb growth. Note too that excessively warm weather will have the same effect.

Growing Conditions

Onions will grow best in lighter soils that are freely draining. Prepare the soil beforehand by digging in some well-rotted manure or compost. You can break up denser clays with a spadeful of sand every square metre or so. Do this in winter to give the organic material time to break down further. Two weeks before sowing in early spring you can apply a general purpose fertiliser. The ideal temperature range for growth is 13 to 25° Celsius.

Onions are far easier to grow from seedlings than from seeds because seeds can take a long time to germinate and are often slow-growing when they do finally sprout. Seedlings are also much better in cold and damp regions. If you want faster and more assured results, then by all means take this shortcut and opt for seedlings. A third option is sets. These are bulbs which have had one year's growth. There is likely to be less choice for sets and some onions can't be grown this way. They are also more expensive. Seedlings and sets can be planted out a little later than if sowing from seed. Only the neck of the bulb should be above soil level. If more of the bulb emerges above ground during the first week or so after planting you can simply push them deeper.

Seed can be sown directly into beds and thinned later, or it can be germinated in propagating mix and the sets transplanted into the beds later. Onions prefer a relatively dry situation with low humidity, good drainage and aeration. For seed-sown plants, thin them out to 15cm apart in rows spaced at 30cm. Plant seedlings using the same spacing. This will ensure good air movement around the foliage and should help to minimise fungal problems. Spring onions and other upright types with narrow bulbs don't need to be thinned out and can be planted closely together.  

Water & Nutrient Requirements

Onions can be susceptible to a number of bulb rots, so don't over-water your plants. In overly wet conditions try growing them in raised mounds. You will need to water them during dry weather, but ease off when the bulbs begin to ripen. Reasonably high levels of potassium and nitrogen are needed and this can be obtained if the soil is prepared as described above. No further fertilising is usually needed but if they do require a boost during the growing season then they respond better to inorganic or fast-acting fertilisers than to slow-release organic types.


Stop watering bulb-forming onions when bulb has attained its full size. This is usually after about six to eight months. You can tell that they have reached maturity because the leaves will tend to flop over. Allow the tops to almost completely die down and then lift them. The bulbs can be left to dry for a few days before twisting the leaves off and rubbing off the roots. They may now be stored. A cool dark place is ideal. Allow them to air in wire trays or suspended in onion bags.


Too much water can cause fungal problems. Onions can be prone to quite a few diseases such as downy mildew, fusarium wilt, botrytis, smut, rots, and several other viral and fungal problems. Downy mildew causes leaves to go a greyish colour and flop over. White rot may be noticed as yellowing of the leaves. Smut turns the leaves a dark grey colour with black stripes caused by spores. Most of these diseases can be avoided with good hygiene practices like providing adequate drainage and aeration and choosing varieties suited to the local temperatures. The application of a suitable fungicide when sowing seed is also beneficial for disease management.

There are some other rots which affect stored bulbs causing them to turn slimy or develop blue-black marks between outer scales. Again, drying bulbs for long enough and correct storage techniques will minimise these problems.

The main insect pests of onions are aphids, thrips, onion fly maggots, eelworms and cutworms (moth caterpillars). Onion fly maggots burrow into bulbs and eel worms get into both leaf and bulb tissues causing distorted growth. Insecticides may control maggots. Remove all bulbs at the end of the season to get rid of food sources for onion flies. Thrips may be controlled using predatory mites or overhead watering.


To complete the course, you are required to complete an assignment at the end of each lesson.

There is also an exam to complete at the end of each module, so six in total. Exams are taken at a time and location to suit you.


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