Crops produced in today’s modern greenhouse ranges are many and varied. They can be loosely categorized as follows:
- vegetables including tomatoes, cucumbers, fancy lettuces, bell peppers, cherry tomatoes and a host of minor ones such as radish, melon and strawberry
- cut flowers e.g. roses, mums, carnations
- potted flowers e.g. geraniums, azalea, poinsettia, tulip
- numerous bedding plants
Porous, well aerated substrate are used as anchorage for the plants root system and feeding area. Rockwool and Heydite are the most popular as they are most readily available, and easiest to use and transport. There are various other mediums which are not as widely used. Click for more info
There are different ways to bring water to the plants. Learn more about growing techniques.
- Nutrient Film Technique,
- Drip-Irrigation or Micro-Irrigation,
- Aeroponics / Deep Water Culture,
- Flood & Drain,
- Home Hobbyist Systems,
- Passive Planters / Hydroculture.
Carbon Dioxide Enrichment
In an outdoor garden the CO2 level in the air is about 300 parts per million (ppm). Plants thrive when they are able to take in a higher level of CO2. Growers today monitor their greenhouse CO2 levels with special purpose control monitors which in turn operate CO2 burners or generators to replenish CO2 consumed by the plants.
HAF (Horizontal Air Flow)
Working with CO2 enrichment and indeed an important part of the greenhouse environment is horizontal air flow. Conceived in the late seventies following research involving finer aspects of greenhouse air circulation, horizontal air flow, or HAF as it is now referred to, is widely used.
Commercial growers end up with very sizable portions of their yearly turnover as work-in-process. The closer the crop gets to harvest, the higher the risk of catastrophic loss, should a key part of the greenhouse’s climate control system fail. Accordingly, growers go to great lengths to protect themselves. Early warning is a vital part of their security. Most now employ automatic phone dialers with electronic voice simulation to alert them of impending problems long before serious crop damage can occur.
Environmental concerns are uppermost in the minds of today’s consuming public. The horticultural industry has been working for many years to reduce its dependence on chemical pesticides, many of which have been linked to cancers. Numbers of key pesticides have been deregistered for particular crops, others have been removed from the market altogether. Promising advances have been made in the use of predator insects in greenhouse ranges as natural biological control against pest insects. While much work remains to be done to educate the grower in their use, progressive members of the industry are now well on their way to 100% biological insect control.
Until recently, pollination of greenhouse tomato crops was accomplished with a laborious method of fruit truss vibration utilizing battery operated hand-held vibrators (“electric bees”) manually touched against mature flower sets. It was a strictly artificial way of simulating natural pollination in the absence of a natural outdoor environment where wind and insects are the vectors. In today’s modern tomato ranges, hives of bumble bees are placed strategically amongst the crop and left to accomplish naturally what has been, until now a monotonous and tedious task for greenhouse staff.
In order to get the best possible results from a Controlled Environment Agriculture System, we will need to bring the spectrum and intensity of sunlight indoors. This is accomplished using High Intensity Discharge lamps. These lamps, in conjunction with specially designed luminaries, will reflect light downwards to plants, where it may be utilized to the maximum. Click for more info.
Modern greenhouses employ advanced environment control aids such as relays, humidistats, thermostats, CO2 injection systems and fans which are often controlled by a central computer. Smaller systems employ various individual control units.
The organic hydroponic display or Bioponics, we believe, is of significant interest to both commercial and hobby growers. This method employs an organic tea based nutrient solution with added microbial agents to facilitate their breakdown into mineral elements which plants are able to take in.
Today’s commercial greenhouses are constructed of galvanized steel, extruded aluminum, fiberglass, polycarbonate, acrylic, polyethylene and glass. The percentage of each, comprising a typical structure, varies by type of design.
Loosely categorized, the following basic shapes and styles are prevalent:
- freestanding grade to grade hoop houses (quonset) clad in polyethylene, double polyethylene, corrugated fiberglass sheet, or plastic composite structured panels
- linked or gutter-connected straight-wall hoop houses clad in polyethylene, double polyethylene and so on as above
- linked or gutter-connected straight-wall hoop houses clad in curved automotive glass
- linked or gutter-connected straight-wall peaked houses clad in flat tempered glass. This style of range breaks down into three further sub-categories:
– single peak gutter-to-gutter
– double peak with floating gutter
– triple peak with two floating gutters
All of the above styles or designs of greenhouses are popular, the grower selecting which he will build based on crop to be grown, usage pattern, seasonal pattern, as well as economic considerations.
- Nutrient control insures that the plants get the minerals they need at the right pH and temperature.
- Faster growth then soil grown plants.
- No weeds. The medium is mostly inert and unless it is out doors, there is no way for weed seeds to get into the growing medium.
- No guess work about what nutrients are going to the plant.
- Easy to correct for plant deficiencies.
- No backbreaking soil conditioning.
- The water has all the nutrients that is required by the plants. The roots don’t have to grow bigger looking for food. The growth of the plant goes mostly to the upper plant.
- Plants can be spaced closer together then in soil. Spacing is dependent only on the space needed to supply adequate light to the plant.
- Garden can be at a good working height.
- Up to twenty times the amount of plants can be grown in the same space in hydroponics then in soil.
- No soil to harbor bugs.
- Healthy plants have better taste.
- Healthy plants resist insect infestations. Less insecticide is needed.
- Educational for children of all ages learning about plant growth.
- Faster growth so that more then one crop can be raised in a season.
- Can be made portable so that you can move it from classroom to classroom or take it with you when you move.
- Ground is left undisturbed on rented property.
- Condensed growing methods make better use of greenhouse space.
- Consumes 1/10 the water that field crops do.
- Conversation piece.
- Good past time for those that likes to tinker.
- It’s something the Jones’ don’t have. 🙂
Some disadvantages to growing plants in hydroponics are;
- Higher cost to get started then soil culture.
- System failure could result in a lost crop if not caught right away. Some systems can go days before damage occurs.
All the plants needs are supplied by water. The roots are placed in an inert growing medium. Water, enriched with all the nutrients the plants need, is supplied to the roots by several different methods.
Aeroponics; the roots are sprayed with the nutrient solution. This method ensures that the roots get plenty of oxygen to the root system. It has not been proven that this method helps to make plants grow any faster then in other methods. It has some inherent problems such as nozzles getting plugged up. One of the more expensive methods of hydroponics.
Ebb and flow; also called flood and drain. Periodically floods the medium. As the water drains out new air comes in. Not as hard to maintain as an aeroponics system. Roots can plug up waterways however.
NFT; the Nutrient Film Technique is one of the methods most often used by commercial growers. Plant roots are contained in a channel through which a thin “film” of nutrient solution passes. The nutrient solution is aerated and recycled with the addition of makeup water.
Run to waste; in this method the nutrient is fed to the plants at near the same rate as the plants use the water. In all the other methods, the nutrient solution returns to a tank to be recycled. This system is the cheapest to get started, however, it requires a lot of monitoring to insure the plants are getting enough nutrient but at the same time not getting too much nutrient. Plants will only take up the nutrients it needs. On sunny days they take up mostly water and leave the nutrients behind to build up. The built up salts must be purged from the system one or two times a week. This system wastes the most nutrients.
Plants most generally have to be stared in a small amount of medium before they can be placed in the growing area. Seeds are started with no nutrients in the water. Seeds have their own food and don’t require any additional nutrients until the first set of leaves appear. Nutrient is added at half strength to encourage root development until it’s transplanted. Then full strength nutrients are used for the rest of the plants growth. There are two kinds of formulas for plants. One promotes the vegetative growth and the other promotes Fruiting. A system that has both types of plants will have to have one or the other formulas depending on which crop is more important. There are two methods of growing systems, horizontal and vertical. The following are systems:
Bag culture; used commercially in run to waste systems. The hobbyist can also use this inexpensive method in a recirculating system. Bags are filled with a lightweight medium and nutrient is fed to each bag by inexpensive spaghetti tubes. Has the advantage of being able to space the plants as they mature.
Gutter/NFT; A lot of hobbyists have tried just about everything with this type system.
Manufactured channels; Square corners help to prevent damming.
Rain gutter; Metal gutter can oxidize and add undesirable materials to the nutrient solution. Line with plastic sheet. Plastic gutters require total support to keep it strait.
PVC pipe; most hobbyists use PVC pipes with holes drilled for plants. This system is usually more expensive then bag culture. Too often the roots clog up the waterways and dam the water causing root rot. Aeration in the root zone may become a problem.
Beds; are extra wide channels. Beds can be filled with a growing medium or pots can be placed in the bed so that they will pick up the water from the bed through a wicking action. Pots are the most versatile. Plants can be spaced to meet the plants needs. I use this method for houseplants and for starting seeds. A 1/4 inch of water can be maintained in beds with pots. Water must be drained well in filled beds. Beds can be made from any material that will hold the weight of the plants and the medium. A plastic film can be used to line construction. Nutrient solution is usually aerated and returned to the bed.