Benches

Benches serve an important function in the operation of a greenhouse. Benches are stable, well-drained platforms for growing plants. When properly placed, they are easily accessible to the greenhouse worker for irrigation and other plant maintenance tasks. Because of operating expenses within the greenhouse, it is imperative to maximize usable space through appropriate bench placement.

Under certain circumstances, plants can be grown directly on the floor of the greenhouse. This method requires that the floor be well drained. This technique is well adapted for bedding plant growers in large units. But the constant bending may be tiring for greenhouse workers, and injury can result. Because of the impracticality of the use of the greenhouse floor for growing plants, the use of benches is recommended.

Labor concerns, such as bending and reaching, operating costs, and irrigation methods used, and ease of movement throughout the structure are usually the driving forces behind the choice of benching to be used. Many aspects need to be considered prior to the installation of greenhouse benching. The following table lists some of these considerations:

Considerations
Bench height
Handling plants and mechanization
Air spaces in surface
Allow water to drain off the surface and air circulation reduces disease incidence
Strength
Must support high weight loads
Compatibility with irrigation system
Adapted to irrigation technologies (including   ebb-and-flow or   food floor)
Cost
Design and material needs to be economically adequate with crops being grown
Support requirement
Depending on bench surface, the type of structural support will vary (expanded metal is rigid and need less support than wire).

 

I. Bench Arrangement: Peninsular vs. Longitudinal Design, Rolling Benches.

The peninsular design is used when the growing area needs to be maximized. This design is of particularly interest for pot grown plants because it allows for convenient segregation of species which is advantageous for retail growers. A major advantage of the peninsular design is that routine tasks including watering, steam sterilization, fertilization, and plant harvest become easier to do with a peninsular design than with longitudinally placed benches. This is especially true in research greenhouses where different treatments are applied simultaneously. The large central corridor allows for easy manuevering of carts or people, and the distance from the edge of the bench to the center is reduced.

Rolling benches are another way to increase space efficiency. They allow up to 90% of the floor space to be used for growing plants. They are easily moved and are a more efficient use of space in small greenhouses. However, rolling benches are not appropriate for retail settings or when the plants need to be accessed frequently.

John Kumpf on Rolling Benches—

"Here, we are looking at expanded metal rolling benches. One of the nice things about the expanded metal bench top is that you get a lot more air flow up and around the plant material. In this picture the benches are rolled together, with no aisle in-between. In the second picture, they are rolled apart. This creates a temporary aisle so you can get in between benches for watering."

II. Bench Space Efficiency.

Bench space efficiency is defined as the ratio of the area (sq. ft) covered by benches to the area of the entire greenhouse expressed in percentage.

Benching Space Efficiency = (bench area/ total area)* 100

Some examples

 

Usually peninsular bench arrangement will increase the growing area even more, and even greater efficiency can be realized with rolling benches by eliminating walkways. Note that rolling benches can also impede plant access, but there are some designs that help the transportation of plant material.

 

III. Bench Support

Regardless of the type of material chosen for the bench, a good rule of thumb is to allow support for at least 25 pounds per square foot area. A list of advantages and disadvantages can be viewed in the following chart:

Material
Advantages
Disadvantages

- Longevity and resistance to rot/decay

- One time cost

-Lower maintenance cost

- Expensive to install

Wood

( locust- cedar-redwood-cypress)

- Resistant to decay (resistance can be improved if benches are painted with copper naphtanate or other presevatives)

- It wraps and absorbs chemical that cannot be removed

- Higher maintenance

- Durable

- No additional treatments to prevent decay

- Permanent and do not allow change later

The supports going across these benches are about a foot apart. The cross supports for most commercially available expanded metal benches are further apart but in this case a narrower spacing is necessary to bear an unusually heavy load. When using expanded metal on the bench surface, you want to make sure that it doesn't bow in-between the supports..