Growing It: How to Grow Broccoli in Zimbabwe

Thursday, June 22, 2017

Broccoli_Production_in_Zimbabwe

Broccoli ( Brassica oleracea) is part of the brassica family which includes cabbage, cauliflower, kale, rape, turnips, kohlrabi and Brussel sprouts.

Broccoli's growing habits are most similar to those of cauliflower. It has the same upright structure, leaf habit, and head formation as cauliflower. Broccoli, however, is much easier to grow than cauliflower but not quite as easy as growing cabbage.



There is a growing interest in broccoli consumption because of it is a nutritious crop. It is rich in magnesium, iron and calcium.  It is also a good source of Vitamins A and C. Vitamin A is usually lacking in most Zimbabwean diets. Broccoli can be a good addition to consumers' recommended 5 a day (fruit and vegetables) needed for a healthy diet. The World Health Organization (WHO) recommends that people eat at least 400g of fruits and vegetables per day.

If there is a good demand in your area broccoli is worth considering for your autumn/winter production.

At a Glance



Broccoli Types and Variety Selection

There are three main types of broccoli that are grown today:

  • Calabrese: annual green or purple broccoli ( less common). Calabrese is the most common type of broccoli. It forms a multi-floreted head with a diameter between 10 and 20 cm with thick stalks.
  • Romanesco: maturing in late summer and autumn, with various yellowish-green conical groups of buds arranged in spirals
  • Sprouting broccoli: an early overwintering annual or perennial, ready in early spring, usually available in white or purple.

Variety Selection

There is no one variety that performs well across all planting seasons and areas. Choose cultivars that suit the climate in your area.Talk to your Agritex officer or farmers in your area to determine which varieties of broccoli grow best in your area.

Vegetable seed companies such as National Tested Seeds, Charter Seeds (distributor of Starke Ayres) and Klein Karoo Seed Marketing are always developing new seed varieties. Contact them to inquire about good varieties for your area, taste and disease tolerance. Also, check with your produce buyers about the preferred varieties for their customers.

If you are a new grower we recommend that you buy seedlings (transplants)  from a reputable commercial nursery instead of starting from seed. Transplants speed up your start up process to establish your crop and help you get an evenly (uniform) maturing crop.

Finalise your preferred varieties, and planting schedule and order and buy disease-free transplants. Calculate the number of plants your need and order your transplants. You need about 45,000 plants per ha. Order your seedlings ahead of time, this will give you the best chance of getting the varieties and quantities you want when you want them.

Here are 5 top performing broccoli varieties from leading seed breeders and distributors to try:

Topaz: this is a hybrid seed variety. It is suitable for the fresh, processing and pre-packing markets. Matures in 65-75 from transplanting (summer) and 90-120 days (in winter). Perfect for year round planting and has good heat tolerance. Topaz has small to mid-sized beads, dark-green in colour, and dome shaped. Excellent yield potential. Available from Starke Ayres/ Charter Seeds.

Diamond: this is a hybrid seed variety. Diamond is multi-use suitable for the pre-packing, fresh and processing markets.  It matures in 60-70 days from transplant (in summer) and 90-110 days ( winter). The plant produces heads that are compact, medium-sized, green in colour, very uniform and dome shaped.  Suitable for summer and winter planting. Excellent yield potential and has good heat tolerance. Available from Starke Ayres/ Charter Seeds.

Star 2204: Hybrid seed. Suitable for the fresh and processing markets.  Matures in 60-7o from transplant (summer). Medium to large frame. Good disease resistance, good heat and cold resistance. Highly adaptable and suitable for year-round production. Firm, dome-shaped heads with short to medium florets. High marketable yield potential, yield potential of between 8 and 12t/ha. Available from Starke Ayres/Charter Seeds.

Belstar: this is a hybrid seed variety. Belstar yields good results for the pre-packing and fresh markets. It matures in 70-85 days (summer) and 90-100 (winter). The plant produces heads that area dome-shaped, medium sized and green in colour. Well suited for autumn, mild winter, spring and mild summer planting. Available from Klein Karoo Seed Marketing.

Batavia: this is a hybrid seed variety. Matures in 75-85 days (summer) and 90-110 days (winter). Dome shaped, green coloured curds, firm and medium-sized. Suitable for planting in the autumn, mild winter, spring or mild summer. Good fo the pre-packing and fresh markets. Available from Klein Karoo Seed Marketing.

When to Plant Broccoli


Broccoli grows best in cool to mild temperatures of between 15 and 25 degrees C and cool nights with temperatures between 10 and 15 degrees C.  The best temperature for seed germination is 10-25 degrees C.While broccoli is frost hardy heavy winter temperatures below 4 degrees C can damage broccoli heads and young seedlings.

Growing broccoli in the autumn/winter or spring is better than growing in the summer because pests and disease can be more difficult to manage in summer production. Warm temperatures can also cause quality problems such as poor head quality.  These problems make growing broccoli in the summer in most areas not commercially viable.

The best time to plant broccoli in most parts of Zimbabwe, especially for new farmers, is from mid-February to August. Experienced farmers in cool parts of the country can probably grow broccoli year round.

Where to Plant Broccoli


Choose a sunny position that gets at least 6 hours of direct sunlight, though broccoli can tolerate partial shade.


Plant in a site that is protected from the wind. Broccoli is easily damaged by strong winds and needs a windbreak. You can grow forage sorghum or use temporary tree breaks across the field to provide your broccoli plants with some protection.

Do not plant broccoli on land where you previously planted brassica crops such as cabbage or cauliflower. Rotate your crop with other crop families such as Solanaceae/nightshade crops (such as tomatoes, potatoes, eggplants and peppers.) Crop rotation helps to decrease disease infestation and pest management costs.

Soil and Land Preparation


Broccoli demands rich, well-drained soil. It prefers slightly acidic soils with a pH range between 6.0 and 6.8 but can tolerate alkaline soils of up to 7.5. In this range, most major and trace elements present in the soil are available to your plants, without being at toxic levels.

You must have your soil tested to determine your soil pH.  Soil pH measures the soil alkalinity or acidity of your soil on a scale of 0-14. You can learn more about soil pH and testing here. It is important to do a soil test at least once a year.

Broccoli grows best in moist, non-compacted soil. To develop a nice head of broccoli requires plenty of rich soil that contains plenty of nitrogen (N).  You should add between 25-50 tonnes of well-rotted compost and manure to help improve your soil's organic matter and structure.

Prepare your land well before planting. The choice of equipment you use to prepare your land will depend on the size of your land and your budget. If your land has a lot of grass or weeds you need to plough or disc cultivate it before you plant. If the previous crop was fibrous, slash it before incorporating it into the soil.

Aim to produce friable soil. The soil should have no clods, weeds or crop residues. Avoid working the land when it is wet or very dry. If the soil is too dry during cultivation it will damage the soil structure. If the soil is too wet during cultivation it will lead to compaction.

Steps for preparing the land for planting:

1. Cultivate the soil using disc or tine cultivator once or twice.

2. Rip if necessary to break up the hard pan. It is best to rip immediately after the final harvest to allow water to penetrate deeply during fallow periods.

3. Add animal manures (cattle or chicken are best) to improve the soil organic matter. Apply organic matter into the soil a few months in advance to allow time for it to decompose.

4. Plant green manures or cover crop such as sorghum in the summer. Sorghum can help dry the soil profile and shatter compacted layers.  It will also help build up organic matter.

5. Slash your cover crop if you planted one.

6. Do a soil analysis: to take out the guesswork of applying fertiliser and to determine your soil pH and your calcium and magnesium levels.

7. Incorporate your cover crop ( e.g. sorghum) and lime, dolomite or gypsum. Lime helps to raise soil pH which helps prevent nutrient deficiency problem. Apply gypsum to alkaline soils it will increase calcium levels not change the soil pH.  Dolomite or lime is best applied 2-3 months before planting or when the previous crop or cover crop is incorporated into the soil.

8. Final land preparation using disc or tine cultivators and bring it to a clod-free, weed free and all previous crops.

9. Apply basal fertiliser before planting by banding along the intended rows and incorporating it during bedding up.

10. Prepare raised beds using ridger after disking and ploughing. Bed widths are typically 90cm and bed lengths vary depending on your own preference. Preparing raised beds improves drainage and air circulation which reduces disease and pests.

Planting Your Broccoli


You can direct seed (sow) or transplant broccoli. When you direct seed your broccoli you need to ensure that your crops germinate evenly to make harvesting easy and reduce the number of passes needed to complete your harvest.

If you are starting from seed sow your seeds in a fine seed bed. Use a dibber or stick to make planting holes. Follow the directions on the seed packet for planting depth and spacing. Cover the seed lightly with some soil. Cover the seedbed with dry straw until the seeds germinate then remove the grass. Lightly irrigate the seedlings daily.

Harden the seedling before transplanting. Hardening off is the process of gradually exposing seedlings to field conditions in order to reduce the risk of transplant shock.

Only transplant healthy, good quality seedlings. Discard any leggy and unhealthy looking seedlings. Irrigate your beds before you transplant the seedling. Transplant in the morning or early evening when it is cool.

Space plants 300mm along the rows. Make rows 550mm apart. Plant in double rows with 1.5m distance from bed centre. Try to avoid high-density plantings because it makes disease and pest management more difficult.

To supply a consistent amount of broccoli to your customers you can practice succession planting (stagger your planting).  Direct seeding or transplanting small quantities on regular basis.

Days to maturity vary by season and variety between 70 and 120 days. Yields vary depending on climatic conditions, pests and diseases, variety, season and planting density.

Mulch seedlings to help keep them moist especially when temperatures rise.

Watering Your Broccoli


Effective irrigation is critical for optimum productivity of quality broccoli or any other commercial vegetable production. It is important to consider and choose an irrigation plan for your broccoli. Broccoli is usually watered using overhead irrigation though you can use other forms of irrigation including drip irrigation.

Effective watering is especially important during the first weeks after transplanting (establishment phase) because broccoli has shallow roots that have a limited capacity to hold water.

Providing inconsistent or inadequate water to your broccoli plants will make them stressed, dry out and wilt. This reduces a drop in yield and quality more susceptible to pests and disease and not reach their full potential. Aim for an optimal application of about 35mm of water per week.

For effective watering, once your plants are established use your fingers or a tensiometer to check your soil moisture.  How often you plant depends on how hot it is, your soil type or growth stage. Broccoli requires ample water during the establishment and flowering stages.

They are times your broccoli plants need more water than other others such as immediately after sowing or transplanting and when they are flowering. Water the plants deeply and consistently. It is important that the water reaches the roots. Mulch the crops to help retain water.

The best time to water is first thing in the morning so moisture has a chance to sink into the soil before evaporating. The second best time to water is in the early evening.


Fertilising Your Broccoli


Broccoli is quick growing and a heavy feeder that needs immediate and adequate access to nutrients for good yields. Give you plants plenty of well-rotted organic matter (compost or manure)

Feed your plants with fertiliser. Take a soil test and base your fertiliser application on your soil analysis. Your soil analysis replaces the guesswork out of fertiliser application so you can base your fertiliser purchases on your own soil and crop needs not random people on Whatsapp. Guesswork typically results in overfertilization and increased costs.

If you cannot do a soil analysis because of time constraints, you can use the following as a guideline:

Apply basal fertiliser at a rate of 500 kg using Compound C just before planting.  It can produce good results as a basal fertiliser. For the top dressing, apply 300 kgs of Ammonium Nitrate (AN) which is split applied at 3 weeks after planting at a rate of 150 kgs then another application at 6 weeks after planting at 150kgs per hectare.

Weed Management 


To produce the best yielding broccoli plants you must control weeds, especially during crop establishment. It is still important to implement a weeding plan for your broccoli crop.

The first step in a weeding plan is to plant into a weed-free seedbed. Keep your fields weed free by ensuring weeding is carried out at least once or twice per month depending on weed pressure.

Prior to planting, you can use cover cropping and crop rotation to help reduce weeds. Crop rotations do not allow weeds to set seed.

Irrigate prior to planting your broccoli to germinate weed seeds. You can kill the germinated weed seeds spraying non-selective herbicides or mechanical cultivation.The herbicides you use depend on your planting methods, weed species and crop type.

Other techniques for weed management include flame weeding, mulching using plastic or biodegradable mulch or solarization.

Common Pests and Disease


Broccoli is susceptible to a number of pests and disease. These are usually harder to control in the summer months. It is important to control pests to produce a marketable crop. Here are some common pests and disease that can attack your broccoli:

Pests

Diamondback Moth (DBM): Diamondback moths do not survive in the winter months but are prevalent in the summer time causing production problems. Scout (check) growing plants regularly for diamondback moths. Control: spray plants with Tamaron at a rate of 100ml/100 litres of water. This translates to about 1.5 litres of chemical used per hectare. Ensure that this is carried out after getting scouting results and spray as a Full Cover Spray. Biological control: use natural enemies such as wasps and Bacillus Thuringiensis (Bt).
Cutworms: are greyish, fleshy caterpillars which grow up to about 5cm long and generally curl up when disturbed. Signs of cutworms are evident in plants that are chewed up above or below ground level. To guard against cutworms drench the plants soon after planting by using Karate at 200mls per 100 litres of water. Ensure the whole plant is drenched completely. You can also use barriers or traps such as insect netting to prevent access to seedlings. 
Aphids: these swarms of small, soft-bodied, slow-moving insects that attack the leaves, flowers, pods and suck the juice. These can be mostly seen in shades of green colour in the broccoli field.  High sprinkler pressure can knock them down, but when using pesticides e.g. Confidor at a rate of 50mls per 100 litres will work out fine. Ensure it’s a full cover spray. For biological controls, neem based pesticides or Bacillus Thuringiensis (Bt) are effective against heavy infestations of aphids. You can also spray blast with water if you are planting a small area. 
Common Diseases
Thrips: Thrips are slender yellow/ brownish insects that are about 1mm in length. They feed by puncturing the leaves and sucking up the sap. They leave blisters on the leaves of the plant. As a control, it is of high importance to keep the field weed free at all times. Confidor can also be used at a rate of 50 ml per 100 litres of water as a full cover spray.

Downy Mildew: When the plant is infected with this fungus it shows white fuzzy masses in patches on the leaves particularly on the underside of the leaves, heads and the stems. It can also cause the curds to turn brown/blackish on the stems especially when there is a lot of moisture on the plants. Control: maintain good airflow and keep your plants moist in the afternoons and evenings. If you notice a downy mildew infestation apply Mancozeb at a rate of 1kg per hectare. Apply again after 7- 10 days.
Black Rot: is caused by a bacterium that can live in the soil for a period of up to a year! Humid and rainy conditions favour this disease. Symptoms of black rot are lesions that first appear on the leaf margins. Plant tissue turns yellow in colour as it progresses towards the centre of the leaf. Control: use certified seed from a reputable seed supplier such as Starke Ayres or Prime Seeds. The seed will have been hot water treated. Crop rotation is also important. Remove and destroy the infected and surrounding plants.  If you catch the problem early, apply a copper-based fungicide such as Copper oxychloride at a rate of 1.5kg per hectare if necessary and repeat 7-10 days later. 
The best approach to pests and disease is an integrated pest management approach (IPM). 
 Here are some Integrated Pest Management (IPM) strategies for managing pests and disease in your broccoli fields:
  • Practice good farm hygiene: clean tools after use; remove diseased plants and restrict access to production areas.
  • Regularly scout your fields (walk your fields) at least twice a week in warmer weather and once a week in winter to look for signs of disease or insect pressure. This provides a picture of the beneficials (e.g. ladybugs and lacewings), insect pest, disease, virus and weed levels in your crop. 
  • Stay informed about the pests and disease that are prevalent in your area and the temperatures that make them most active.
  • Use cover cropping (green manures) and strategic crop rotations with other unrelated vegetable crops such as pumpkins, tomatoes, potatoes, peas, maize and watermelon. Crop rotations can help reduce soilborne diseases and improve your soil structure.
  • Remove all crop residues immediately after harvest and incorporate them into the soil.
  • Plant on raised beds to improve drainage and air circulation.
  • Use floating row covers to protect seedlings for pests and disease.
  • Timing is important. Grow broccoli in the right time and avoid hot weather production; select the right variety for the growing season.
  • You can companion plant your broccoli with beneficial crops such as dill, rosemary, chervil, beans, onions and potatoes to ward off aphids. Companion planting is based on the theory that certain plants repel certain pests when planted near other plants.
  • Apply the recommended chemical pesticides as a last resort or when pests will cause economic damage. Make sure that you apply spray safely and as directed while wearing protective clothing. Only use chemicals for their intended purpose and note expiration dates. 

Harvesting and Storing Broccoli


Broccoli should be harvested as soon as they reach maturity to avoid overexposure to sunlight which may cause your broccoli to turn yellow making it not fit for market.

Harvest in the morning before the broccoli heads get too hot. Be careful during the harvesting process not to damage your crop and handle it with care. Use a sharp knife to cut mature heads. You may need to do multiple passes to harvest your crop.

Pick, pack and place your broccoli in a shaded area within an hour of harvesting it to prevent it from wilting due to field heat.  When storing your broccoli, ventilate the storage room and maintain a humidity of 95% RH. Your broccoli can store for about 2 to 3 weeks if you maintain a temperature of 0 degrees C.

Broccoli is very sensitive to ethylene gas, which causes yellowing and opening of buds. This happens when you store or transport broccoli with fruits and vegetables such as apples, pears, tomatoes, stone fruit and capsicum which give off ethylene gas. Ethylene gas can reduce your broccoli's shelf life.

The average yield ranges from about 8 to 16 tonnes depending on your crop management.

Marketing and Sales


Broccoli can be eaten fresh or cooked. Most broccoli production is primarily grown for the local market.

When marketing your broccoli, the Broccoli heads must be clean, fresh, domed and have firm, small/medium buds ( about 8-14cm). Check with your buyers for their preferred packaging and head sizes. You can pack your broccoli heads into medium sized punnets and then wrap them with perforated cling-on wrap before storing them in a cool room.

Explore different market destinations prior to planting and get to know your market well. You can plant a small demo area, take a sample to a buyer and then increase your area of production once you have an order. Some options for supplying your broccoli are the fresh, processing and pre-pack markets.

If you plan to sell at the fresh market e.g. Mbare, you must understand that prices fluctuate based on supply and demand.  When there is an oversupply of broccoli the price goes down and when there is a low supply the price goes go up. Check ZFU's weekly price listings or the Agricultural Marketing Authority for current market prices and to avoid getting low balled.

Identify and make supply arrangements ahead of time with major supermarkets such as Pick n Pay, Fruit & Veg City, Shoprite etc. They should ideally offer you an "Order Voucher" which outlines the quality and standards they expect. If your broccoli does not meet the supermarket's quality standards it can be rejected and you will have to find an alternative market option such as selling to vendors.

It is important to be a good supplier. The key to being considered a good supplier is based on your ability to supply quality product consistently and to maintain good communication with your buyers. Provide your buyers with a regular update about your production and alert them if you have any production challenges.

Make your transport arrangement ahead of time. Lack of planning for your transport can break your farm due to high post-harvest losses.

Happy Farming!

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About the Authors

Kevin Jena is a farmer with experience with commercial vegetable production and a passion for feeding the nation.

Eleanor Manske is the co-founder of Emerging Farmer. She grew up on a farm and has worked in agricultural development, policy and marketing in the US.

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