Things on reproducing cuttings & how to automate new plants into trays

In the horticulture and nursery industry, “plant cutting" is a phrase that is frequently used. It can be confusing when it comes to understanding what it means.

According to Wikipedia, "plant cutting" can be used as a noun which refers to is a piece of the source plant that is used in horticulture for vegetative propagation.

"Plant cutting" is also a technique for propagating a plant. A piece of the source plant called a “cutting” is dipped in hormone powder then placed in growing media so it can grow into a plant in its own right. The "cutting" produces new roots and stems and then becomes a new plant. The whole process is called "plant propagation".

In this article, "plant cutting" or "cutting" refers to the process and we are going to explore how to automate this process  of placing (plant) cuttings into trays that can be reproduced from asexual vegetative reproduction

What happens to the new plants during and after asexual vegetative reproduction?

According to Science Learn, the new plants have the same genes as the source plant. Take strawberries as an example. They have stems called stolons which usually grow out sideways above the soil while new plants grow up along them.

Other plants can develop underground stems which are called rhizomes. Rhizomes produce new plants at a distance from the parent. Tubers (e.g. potatoes) and bulbs (e.g. onions) could also have underground stems that can grow into new plants.

When it comes to making new plants using asexual reproduction, nurseries grow plants from cuttings taken from a parent shrub. What horticulturists do is snip a young shoot off a plant, dip it in rooting hormone and then place the cutting in a mixture of sand & potting mix or alternatively into a plug. The plant cutting grows roots quickly and then it can be potted up and transferred outdoors.

What are the requirements for stem cuttings in propagation?

According to NC Cooperative Extension Resources, in terms of propagating woody ornamental plants, propagation by stem cuttings is the most commonly used method.     

It is very important to maintain high humidity around the cutting during the propagation process. 

Production nurseries usually place cuttings in plastic or foam trays/cells. These are commonly covered by clear plastic stretched over a wire frame to keep the humidity at a high level while reducing water loss from the cuttings. Having holes in the bottoms of the trays is a must to help with drainage.

How many types of cuttings are there in nursery propagation?

The research study "Raising native plants in nurseries: basic concepts" illustrates that depending on when the cuttings are collected, there are 3 types of cuttings used in nursery practices:

1. Hardwood - Cuttings are collected during the winter time
2. Softwood - Cuttings are collected in the spring and early summer when shoots are actively growing and leaves are present.
3. Semi-hardwood - Cuttings are collected in late summer and early fall when shoot tissue has hardened and terminal buds are set.

5 x steps to manually reproduce young plants in nurseries

According to "An experience on the automation of plant cutting technique for propagating plants" research study. There are 5 steps to follow to reproduce cuttings into trays.

Step 1: The cutting of the parent plant

Parent plants are used for obtaining newly grown branches, which can then be used for producing cuttings. The task should be done very quickly - cutting the shoot then placing the cutting in the substrate to minimising the loss of water.

Step 2: The stem cuttings

After the parent branches have been cut, each new cutting includes at least one leaf node, near the base of the cutting is needed for producing the new roots. Same as with step 1, hydration is very important so soaking them in water sometimes is necessary.

Step3: The removal of the leaves

The leaves from the stem on the basal part of the cutting should be removed, to prevent the leaves from being inserted or coming into contact with the substrate, which may cause some problems to the new plants

Step 4: The plant hormone subministration

In this step, the cutting basal part is to be immersed in a plant growth substance so the formation of roots can be promoted.

Step 5: The insertion of the cutting in the substrate

The final step is to put each cuttings in a cell of multi cells tray. A substrate is used in the cells to promote rooting and to prevent roots from breaking off.

The 5 steps above to reproduce young plants in nurseries is usually done manually by staff, to reduce costs, improve production efficiency and quality, automation needs to be introduced.

How to automate cuttings into trays that is beneficial to a nursery?

There is research presently being done overseas and prototypes are being developed to automate the plant cutting process. Take ornamental plants as an example:

The ornamental plants automatic cutting process would be as below: the automatic process looks like this:
 

1. To start off, a branch is manually inserted inside the machine;
2. The machine senses the presence of the branch and feed the machine with the branch, which minimise the effect of the curvature;
3. The machine moves the leaves gently so that the leaf nodes are located by the sensors;
4. The machine removes the leaves just in the basal part of the cutting;
5. The machine executes the cut of the cutting using a sharp knife to obtain a clean cut. preserving the leaves in the upper side;
6. The machine immerses the cutting in the plant growth substance and then inserts the cutting into a cell of a multi cells tray.

In conclusion

Propagating plants from plant cuttings is not a simple process and it requires lots of labour, by using a fully automatic machine, the labor cost could be greatly reduced while production efficiency could be massively improved.

The technical solution proposed to automate cuttings into trays is innovative, with the advancement of modern technolgy, robotics and more research it will be only a matter of time before this process is fully automated.

In the mean time there has been various egonomic cutting benches and work stations developed to make the manual process more efficient and easier.