GREENHOUSE CONTAINERS

The containers selected for use in greenhouse potted plant production vary depending on the crop and the time of year.

Pots are round containers whose height and diameter are equal. Made of clay, styrofoam, or hard plastic, they are used for production and sale. Made in small sizes of pressed peat moss, they are used for rooting, seeding, and transplanting. Azalea pots are round containers with the height three-fourths the diameter. They are preferred by some growers for the production of poinsettias and chrysanthemums as well as azaleas. Pans are containers the height of which is one-half the diam­eter. They are preferred by some growers for bulbous flowers such as tulips and hyacinths.

Clay containers are porous; plastic is not. Therefore, gas and air can permeate clay containers, and soil dries more rapidly. This is advanta­geous during the winter season when plants can often be too wet in the nonporous plastic containers. The situation reverses in the warmer months when clay may permit soil to dry out too quickly. Although popular for centuries, clay containers are declining in use by growers.

Plastic containers may be either hard or of styrofoam. Either is much lighter than clay and is often a reason why plastic is preferred by a grow­er. Plastic containers cannot be heat pasteurized, though, whereas clay containers can be heated without fear of their melting. Also, the combi­nation of lightweight container and artificial soil can result in top-heavy plants; so clay containers will probably always have their proponents (Figure 20-4).

Peat pots are manufactured either individually or in strips, similar to egg cartons. They range in diameter from one and one-half to four inches. They are a great convenience for transplanting because there

is no need to remove the pot. It is set directly into the new container or garden, where it decomposes. The peat container is fragile, especially after being wet, and will not tolerate much movement. Growers usually place them in flats (which will be described shortly) to provide the sup­port necessary for moving and handling. Peat pots and strips (Figure 20-5), are widely used for the production of bedding plants. They are also used for the production of lining-out stock (these will be described in Chapter 21).

(a)

(b)

figure 20-5A and B. Square and round peat pots and production strips ((a) © Rick Seeney, 2009. Used under license from Shutterstock. com)

((b) ©Thomas A. Perkins, 2009. Used under license from Shutterstock. com)

figure 20-6. Examples of greenhouse hanging baskets. The papier mache baskets are given added strength by wire. Others are molded plastic. Half baskets are used against the walls. (Delmar/Cengage Learning)

Molded plastic packs are also used for greenhouse production, espe­cially for bedding plants. They resemble ice-cube trays and are available in different sizes. Since they do not decompose in the soil, plants must be removed for transplanting. They are firmer than peat strips and are salable as they are. They also retain moisture better than peat strips.

Hanging baskets are specialized production containers made of wire or plastic (Figure 20-6). The baskets may be solid or meshed. The mesh baskets require a liner to hold the soil and they drip after being watered. The solid baskets require no liner, nor do they drip.

Flats are shallow, rectangular containers that may be used to start seedlings, root cuttings, or hold less sturdy peat pots and strips. Traditionally constructed of inexpensive wood, often as an off-season job for greenhouse workers, flats may also be made of plastic. The plas­tic flats are manufactured to hold a number of the molded plastic packs neatly (Figure 20-7).

Understandably, the size of the containers determines the amount of pasteurized growing medium needed at the time of planting and transplanting. Table 20-1, developed by Dr. P. A. Hammer of Purdue University, can help growers determine their needs in advance.

figure 20-7. Examples of greenhouse flats. The plastic flats are lightweight but strong. The traditional wood flat is sturdy but heavy by comparison. (Delmar/ Cengage Learning. Photo by Jack Ingels.)

Number of Pots Filled with One Cubic Yard of Medium

Container (Diameter in Inches)

Number Filled Per Cubic Yard

Standard round pot

21/4

6,952

21/2

4,840

3

2,948

4

1,276

5

704

6

396

7

242

8

176

12

44

Azalea pot

4

1,540

5

770

51/2

648

6

440

Bulb pan

5

1,100

6

858

Hanging baskets

8

324

10

135

Flats

111/2 X 211/4 X 21/4

85