Plant Propagation Structures

Different Types of Plant Propagation Structures

Plant propagation structures or the facilities required for propagating plants can be broadly divided into two units.

The first one is the structure which helps with the germination of seeds and the development of roots from stem cuttings. These structures need to have ample lighting temperature control, and optimum humidity. Greenhouses and hot houses are examples of such structures.
The second unit is the structure for hardening young tender plants. These plants are kept in such structures so they get hardened before they are transplanted in the fields. Cold frames and latch houses are examples of such structures.

Both these units serve both purposes for some plants and species.

Greenhouses and Glass houses

Greenhouses or glass houses are common propagating structures used. These structures can be made from wood frames, steel fittings for tresses, all metal pre-fabricated aluminum, etc.

The structure varies from small – known as greenhouses to large and sophisticated glass houses.
The small structures are 10 x 10 ft with an average height of 15 ft.
On the other hand, the large ones are 100ft long and 50ft wide. Its roof is generally slanting and covered with a transparent sheet of glass.
Among other things used in these structures include, propagating benches, germinating trays, etc.
The propagating benches are often attached side by side, sometimes permanently, to maximize space.
Ventilators are provided inside for air circulation. Ridge ventilators are commonly used and sometimes, it is side ventilators.
They are often fitted with exhaust fans.
These days, automatic, thermostatically controlled ventilators are available which will open and close as the temperature fluctuates, day or night.
In areas where sunshine is too much, the inside of the greenhouses is painted with a layer of white paint.
It reflects the radiant light and reduces the temperature hike inside. Plastic sheet coverings are also used for this purpose.

Temperature and Humidity Control System

A heating mechanism is used inside greenhouses to increase the required temperature inside.
Steam or hot water is pumped through pipes that run through the greenhouse.
Sometimes, separate air heaters are also used.
Gas is used indirectly to heat the air or water.
In the summer, a cooling system may also be employed to bring down the temperature. A wet pad installed in a corner can cover a large part of the greenhouse. Exhaust fans are usually kept outside to blow cold air into the greenhouses. In more sophisticated structures, an electrical cooling system such as air conditioning is also used.

Glazing or Covering

Plain or translucent types of glasses are used gor building glass houses. Sometimes fiber glass made of polycarbonates are used.

Plastic covered greenhouses are popular in home gardens. Large commercial gardens use lightweight frames and plastic covers to be more economical and for temporary purposes. The main drawbacks of using pastic coverings are,

They are tighter and can increase the humidity inside

It could cause undesirable water drop in plants due to high humidity.

Hotbeds

Hotbeds are used for raising seedlings from dormant seeds. Seedlings, rhizomes, and leaf cuttings can be rooted in hotbeds.

Hotbeds are nothing but large wooden boxes or frames with slopping, tightly fitting lids made of wood fitted with glass. They are placed in sunny but protected, clean areas. The propagating medium below is heated using steam or hot water pipes.

Hot air is also used in certain hotbeds in greenhouses. Here it is made sure to have shading, ventilation, temperature and humidity control, etc. The size of the hotbeds is 6 x 3 ft. They are suitably sized to place on raised platforms attached to some kind of holding.

Cold Frame

A cold frame is used as a propagating structure for hardening young and tender plants before transplanting into the fields.

The construction of a cold frame is similar to a hot bed except, there is no provision to heat the bottom. A standard glass frame of lightweight plastic material is also used for the lid. The size of the cold frame is generally, 3 x 6 ft.

It should be covered tightly enough to retain heat and high humidity as required. They retain heat from the sun using a transparent covering. Young tender seedlings require high humidity so the coverings are held tighter.

Moreover, they must be protected from winds and animals as well. To protect it from excessive sun, reed mats or muslin cloth

Cold frames are used for conditioning or hardening of rooted cuttings or seedlings. These plants get adjusted to normal environmental conditions while inside the cold frames.

The only disadvantage here is the possibility of the growth of pathogenic fungi especially the soil-borne type because of the high humidity. At the same time, using sterile propagating media and control of the humidity inside the cold frame can help overcome this issue.

Lath Houses

In locations that have hot summers and high light intensity, lath houses are used. They are simple structures to reduce heat and light from the sun.

It is used for hardening seedlings raised from other sources before they are planted in fields. Lath houses cover the planted plants and work as an intermediate step between a cold frame and the field.

Lath houses protect the plants temporarily inside the artificial climatic conditions until they are ready for the real environment. When they are ready, the lath houses are removed. They are used in nurseries to hold shade plants such as Anthurium and Orchids.

Construction of the lath houses

Lath houses are made using cheap wooden materials and aluminum or iron frames. Sometimes, concrete pillars are also used. The size of it may vary and could go up to 7 ft. The sides and top are covered using plastic coverings or mats.

In modern lath houses, special plastic materials such as agro net are used. They are available in different grades of light holding capacity, ranging from 25-75% filtration. They will also have sprinklers for watering and cooling.

Miscellaneous Propagating Structures

Small enclosed frames of glass or plastic are used in the beds to ensure successful rooting of the cuttings. These structures keep the humidity high. Bell jars, polythene bags, etc are some examples. Polythene allows gaseous exchange so a better choice than glass.

These propagating structures must be well-maintained and removed within a day or two after rooting. Otherwise, the lack of air circulation inside could promote fungal and bacterial growth. So sanitation is essential with these propagating structures.