What is a greenhouse?
Greenhouse is a structure (mainly a frame) with a wall and a roof. It can be made of metal or wood. Depending on its use, the covering can either be polythene, glass, or polycarbonate.
A greenhouse prevents heat loss through convection. Once the ground has been heated the heat is retained by the covering material. It is this retained warm air that heats up the plants inside.
What is it used for?
- Used to shield crops from excess heat or cold.
- Protects from unwanted pests.
- Makes it possible to grow certain types of crops all year round.
- Enables a steady food supply.
How long does it last?
On average a wooden greenhouse structure can last up to 7years and a metallic structure can last for 10+ years. This depends on a variety of factors.
Some of these factors include;
- An attack by termites on your wooden greenhouse will greatly reduce its life span.
- Strong winds.
- Thieves destroy the greenhouse cover in order to gain access to your plants.
- Polythene greenhouse cover can last for up to 5years. After his it needs replacement.
How much is a greenhouse in Kenya?
Greenhouse costs as little as KSH 90,000 for a wooden structure and KSH 140,000 for a metallic structure. This is one of the smallest sizes, 8Mx6M.
This price can rise up to KSH 650,000 if you want a larger sized greenhouse. One of the main factors affecting greenhouse prices in Kenya is the ever-rising cost of metal.
How profitable is greenhouse farming in Kenya?
If done correctly, it can be a shrewd investment to undertake. To make profits you need to be smart.
If profit is your main goal, avoid planting crops that are high in supply or easily available to the consumer. Instead focus on high value crops and herbs such as tomatoes, capsicum, mushrooms, onions, garlic, eggplant, oregano, basil.
Also taken into consideration is the season in which you sell your crops. During off-peak seasons, your crops might sell for a higher price.
What are the advantages?
- It offers longer growing seasons. Growing seasons can be extended during colds times.
- Planting can be done in any weather. This is because the plants are enclosed inside. Even if it rains, they will not be affected.
- One can grow a variety of plants.
- Offers protection from pests and predators.
- It is much easier to control the use of pesticides and fungicides.
- Helps to save on water usage.
- You have more plant options to choose from.
- Fresh cut flowers all year long.
What are the disadvantages?
- Lack of pollination. This will affect some of the plants and fruits you grow.
- The initial setup cost is high.
- Some plants carry whiteflies and pests which can easily spread to the rest of the crops.
- Requires constant attention.
What is the best flooring for a greenhouse?
Greenhouse flooring will depend on the medium you choose to plant your crops in.
If you plant directly on the soil then the floor will be bare (the soil itself). This is because some crops will require raised beds. It is still possible to use planting bags even if the floor is bare soil.
If you choose to use concrete, this means you will be planting in pots and planting bags. A concrete floor is easy to clean and walk on. Concrete also retains heat throughout the day.
What vegetables grow best in a greenhouse?
- Squash and Zucchini
- Collard Greens
- Green Beans
What fruit can I grow in a greenhouse?
Now that we know the basics concerning a greenhouse, what is the process of acquiring one?
It is important to request for a site survey to determine;
- Topography. Generally, a relatively flat surface is best when considering where to place the greenhouse.
- Wind direction and windbreakers. This determines how the greenhouse is setup for ventilation purposes.
- Collect soil samples for soil testing. Soil samples are collected and taken to the lab for soil analysis. The tests carried out are a nutrient and pathological analysis.
- Availability of reliable water supply. To ensure the greenhouse plants have adequate water, you need to have a steady supply of water.
Rivers and boreholes combined with pumping mechanisms are a great source of water. Collected rain water stored in water tanks is also a great source of water.
- Accessibility. The greenhouse needs to be in an easily accessible area, since constant care and monitoring is required.
- Security. It needs to be in a fenced or secure location. This deters thieves and vandals from accessing your greenhouse easily.
- What is the cost of a greenhouse site survey in Kenya?
Cost of site survey @ KSH 2,000
Soil testing: Nutrients Analysis @ KSH 2,000
Pathogenic Analysis @ KSH 2,500
Transport is provided by the client and depends on the site location
- Once the payment has been made, delivery takes 3-4 days.
- The metal for fabrication is acquired locally. We use 38MM and 42MM round tubes during the fabrication process. This usually takes 1-2 days depending on the workload.
- For a wooden greenhouse, round timber poles are sourced locally. They don’t require fabrication. This means the delivery time might be shorter.
- After we acquire the metal or timber, we pack everything requested by the client for prompt delivery to the site. These include; greenhouse polythene(cover), tank, drip irrigation kit, seeds, starter package, and a technician.
- Once the whole package is ready for delivery, we inform the client that the package is on route to the site. On arrival, everything is unloaded and work can start.
The technician will source for local laborer’s who will help him during this process. He/She will be responsible for them. They will help with digging holes, erecting and covering the structure.
The land is measured, divided, and marked accordingly. The metallic stands are then erected. They provide support for holding the greenhouse cover and roof of the greenhouse. The cover is held in place using profile and w-wires.
A metallic or wooden stand is fabricated. This holds the water tank. (Only if the client doesn’t have one)
The drip irrigation kit is installed in the greenhouse. The lines per bed and drip spacing depend on what you are growing.
Installation of the greenhouse depends on the size of the project. For small projects, it takes 3 days to complete installation. This includes singular unit greenhouse sizes; 8Mx6M,8Mx12M, 8Mx15M, 8Mx24M, 8Mx30M,16Mx30M and, 24Mx30M.
Larger projects will take more time depending on the scope of the work to be completed. This includes multiple units of greenhouse sizes; 8Mx6M, 8Mx12M, 8Mx15M, 8Mx24M, 8Mx30M,16Mx30M, and 24Mx30M.
Seeds and Seedlings.
The seeds are placed in planting trays containing rich planting media like coco peat or peat moss. Normally seeds germinate for a period of 1-2weeks after which they are transplanted to planting bags.
Harvesting is important because it maximizes crop yields and minimizes loss of quality.
What diseases are likely to attack my greenhouse?
It is important to know the type of diseases that might attack your greenhouse. Early detection will help minimize losses.
Fighting these diseases will also boost your morale and make your greenhouse journey more satisfying.
Sources of greenhouse diseases include;
- Infected soil.
- Debris from previous crops.
- Plants kept all year
- Vegetatively propagated crops.
Some actions taken to minimize greenhouse disease include;
- Monitoring humidity and temperature. This will discourage disease friendly zones.
- Watering plants from their bases.
- Preventing spore germination by cleaning surfaces regularly.
- Giving plants adequate space so that air circulates around them.
- Quarantining new plants until you are sure they are disease free.
- Providing proper ventilation.
- Make sure you sanitize your tools.
- Check the plats daily for signs of disease and discoloration.
Here are some of the diseases likely to attack your greenhouse;
- Fungal infections – Fungal infections like powdery mildew, phytophthora, botrytis and root rot are mainly caused by overly wet conditions.
Don’t leave normal greenhouse plants in water for too long. They should be watered until they start to drain and then allowed to continue drain completely.
- Viruses – Viruses are mainly carried into the greenhouse by plant-feeding insects. Monitor when insects start to appear.
Characterized by discolored yellow rings or mosaic patterns on rings. Virial infections are incurable and affected plants must be destroyed.
- Bacterial infections – Bacterial infections like blight and erwinia are incurable, so if your plants develop water-soaked spots and tissues begin to melt into a sticky, gummy substance, get the sick ones out of the greenhouse and destroy them right away.
Often spread by dirty tools, clothes and containers.
Below is more information on greenhouse diseases;
ROOT, STEM, CROWN AND COLLAR DISEASES
- Wilting, browning, or yellowing of lower leaves
- Leaf drop
- Mushy, brown roots (outer tissues slough off)
- Attacks at the root crown or stem
- Large, wet-looking leaf spots
- Blackened cankers at the stem base
- More likely to kill plants than stunt them
- Root rots
- Brown lesions at the base of leaves attached to cankered stems
- Damping-off (affects seeds and new seedlings)
- Attacks plant stem at the soil line
- Brown to black cankers at stem base girdle or kill plants
- Infected stems have a dry, shriveled, or wiry appearance
- Sunken cankers near the soil line
- Chlorotic lower foliage
- Poor rooting
- Stunted growth
- Blackened roots
- Rotted root hairs and secondary roots
- Starts with pale-yellow leaf spots
- White, powdery spots on upper and lower leaf surfaces
- Irregular, chlorotic, purple areas, or necrotic lesions, followed by a white, powdery appearance on leaves
- Fruit ripens prematurely
- Pre-mature leaf drop, shriveling
- Distorted new shoots
- Stunted growth
- Leaf rolling
- Small, yellow spots develop on the upper sides of leaves while white to bluish and grayish, fuzzy-looking spores and mycelium develop on the lower leaf surfaces
- Infected leaves and branches may distort and die
- Spore colonies can grow systemically throughout a plant
Fungal Leaf Spots
- Tan to reddish-brown to black circular lesions with distinct borders
- Lesions may run together to form irregular shapes or blighting of the entire leaf
- Spots can enlarge and grow onto branches and stems
- Dark-brown necrotic (dead) leaf spots with yellow halos
- Leaf curling and twisting
- Necrotic blotches start at the leaf margins and advance inward
- Death of branch tips, leaves, and blossoms in severe cases
- Gray, fuzzy coating on aging flower blossoms and soft, ripe fruits
- Brown to gray circular spots that later become fuzzy
- Spotting and decay of flowers, leaves, fruits, and berries
- Leaf spots and blights
- Bud rot
- Can cause cankers on roses and other ornamental plants
Ornamentals, vegetables, berries.
- Lower leaves turn yellow and then brown and die
- Browning of vascular tissue
- Stem canker
- Root rot diseases
*Ornamentals – Plants grown for their appearance.
Should I install greenhouse?
Absolutely! A greenhouse is not only used for commercial purposes. A small sized greenhouse installed at your home is a great way to start your journey to food security.
Metallic or wooden greenhouse in Kenya, Kisumu, Nairobi, Eldoret, Nyeri, Mombasa, Machakos, Kajiado, Meru, Marsabit, Bungoma, Uganda, Tanzania, Ethiopia, Somalia, Sudan, Rwanda