Review (Two Columns)

Publications 10 November 2016


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Perfecting the growing medium for successful seedling production and propogation of cuttings.

Growing medium is rated by users according to certain parameters:

a) Cost  

b) Specific crop requirements

Technically speaking, each of the identified growing mediums can in general, support seedling development. The difference is; on what scale, in what climatic conditions and, which type of plant. The intelligent way to approach it is to first understand the plant; its requirements, behaviour and its nature. Then to carefully analyse whether the investment in growing medium (minimal as it might be) really supports the specific plant and will ultimately produce a better seedling.

In fact, medium that is structured and designed for a specific crop will result in a better and higher yield.

To appreciate the above statement; an experienced grower  who specialises in propagation of for example hazelnut tree cuttings will not use “just any medium” just because they can all work or because it is less expensive. The cutting  in this case does require a specific BLEND that will support the Hazelnut nature in the most optimal way; therefore the grower knows that to get best results he will need to use the best blend (irrespective of cost)and this will be non-negotiable.

Why the Blending concept is essential:  

The development of each plant is directly affected by the ability of young plant(seedling) to develop healthy root zone which is a result of correct moisture, oxygen, temperature and availability of nutrients (if roots don’t supply the upper growing parts with nutrients and water, roots won’t get “food” from the upper parts’ factory). 

Since roots are entirely dependent on the “medium” surrounding them, their performance will be accordingly. If the medium support the roots in an optimal way the roots’ response will be optimal. If it is not optimal they will adapt but will compromise on function, resulting in less developed upper parts and eventually low quality seedling.

The BLEND role is to provide optimal root conditions. If the main portion of the growing medium is too porous and its WHC (Water Holding Capacity) is considerably low, it makes sense that blending it with a material with strong WHC, will improve the root zone by creating a moister environment. (For example: 60% Perlite blended with 40% Vermiculite). But if other characteristics are required, the supporting other materials should be added in the correct proportion to create an optimal BLEND.

SEEDLINGS- Growers use various technics to improve and optimise the seedling production. The growers aim is to produce healthy seedlings in a considerably short time cycle, strong enough to be transplanted, sustain health and freshness in transport and to reduce the growing input cost as much as possible. It is understood by experience that growing seedlings in general, vary from plant to plant; one cannot compare mass seedling production of Lettuces to mass production of Forestry seedlings, each has its own requirements and therefore requires different blending. (There is a dramatic difference between seedlings grown in cavity trays and seedlings grown in 5L bags in terms of volume that support roots development and duration).


A challenging task, since plant parts are used for propagation which needs to transform entirely from vegetative part to produce roots. Some or can’t at all go through the process (most temperate climate nuts) some will do it “naturally” (Fig). Since propagating of hardwood and softwood plants required different technique each required perfect growing medium to support the transformation to root production. Olive cuttings will root well in 100% perlite medium for example, while other trees cuttings will not at all or with limited success. In general if all factors involved in the process of transformation to rooting are optimal it will perform the best with high percentage of successful propagation.

Enormous efforts and resources are invested in producing optimal growing blends for specific seedlings and cuttings for no other reason than to provide optimal material that can produce the best results for the growers.

Blends are “tricky” in a way; going through trial-and-error while trying to get it right is sometimes costly and time consuming. It is a better proposition to invest in a quality blend and thereby to improve production and yield. 

Ben Safronovitz

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Last modified on 10 November 2016

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