Rooting Guide

Every day the technical advisors from Rhizopon visit nurseries where plants are being propagated from cuttings. These nurseries are seeking the latest trends and maintain the highest professional standards. After all, the market is demanding ever larger consignments of plants of high quality uniform plants that have to be delivered at previously determined time.

Meanwhile, a rise in price is practically unthinkable. This, and the fact that many production problems can be traced to cuttings of inferior quality, are two of the major reasons why having the perfect system of obtaining parental material (the cuttings) is a minimal requirement.

An important principle is:
A good start (having good cuttings) is necessary for successful production.

	Select the best possible parent plants Years ago, simply taking cuttings of plants growing here and there at the nursery was common practice. Frugal growers even took cuttings from plants in public landscape areas! Naturally (and especially in the latter case), it was impossible to know the condition of the parent plant. Since the best parent plants produce the best cuttings, it is crucial to find a good source of them or to grow them at your own nursery. Apply an ongoing selection process During each growing cycle, make a selection of the plants exhibiting the best characteristics to continue growing. From these, choose the best plants to use as parental material. Select thin cuttings The location at which the cutting is taken greatly affects the speed at which the cutting will root. From the selected plants, take cuttings close to the base of the plant. When taking cuttings from varieties that are difficult to root, it is advisable to select the thinner cuttings since these will root more easily.
	Grow parental plants under controlled conditions Raise the carefully selected cuttings under completely controlled, ideal conditions. When growers give their parent plants exactly what the plants need, the parent plants will deliver exactly what the grower needs: super cuttings. Advantages of tissue culture In most cases, cuttings taken from parent plants produced from tissue culture produce better cuttings than ‘ordinary’ parent plants. What’s more, parent plants produced by meristem culture are free of viruses. Only a well-rooted cutting can produce a good final product.
	Rapid rooting is preferable The faster a cutting takes root, the earlier it will exhibit independence and resistance. A rooted cutting is an independent plant that can produce its own stores of energy. An independent plant is resistant to disease.
	Providing the best possible conditions for rooting A cutting given less than optimal rooting conditions will waste valuable energy. The result will be an inferior root system. To be able to produce its own stores of energy, a plant needs such raw materials as light, water, CO2 and oxygen. Light Since light (whether sunlight or artificial) is accompanied by a rise in temperature, we will be devoting plenty of attention to this factor. Light is necessary for photosynthesis. A cutting without roots is unable to engage in very much photosynthesis, so a little light is sufficient. More important at this stage is to provide a long period of light over a period of 24 hours (at least 16 to 18 hours) than to expose cuttings to bright light which is accompanied by high temperatures. If necessary, artificial light can be used to extend natural daylight hours.
	Water For a plant, water is just as important as blood is to a human being. This is why a good root system that can absorb water is so important for a plant. Give cuttings the opportunity to develop the best possible root system! Available water is also crucial while the cutting is taking root. On the other hand, a substrate that is too dry will cause cell death, and dead cells increase the risk of black rot. Another disadvantage of an overly dry substrate is that it encourages callus formation. Although many believe that callus is beneficial for root formation, the opposite is actually true. Callus hinders and slows down root formation. The degree of moisture in the soil can be measured with a tensiometer. This instrument indicates when the medium is dry, moist or wet. For the best possible rooting, the meter should display a reading between moist and wet. By weighing the trays regularly, you can check to see if they have the proper weight (which can be interpreted as ‘the proper moisture level’). Providing water as based on this information gives the best results in practical situations.
	CO2 Even for cuttings, photosynthesis is important. So, in addition to light and water, sufficient CO2 must be available. Another advantage of an increased level of CO2 in the air is that it reduces the amount of transpiration (loss of water) through the plant. Cuttings in an environment with sufficient light and an increased CO2 level (800 to 1000 ppm) will root better. Oxygen Since oxygen is indispensable for cell division, it is crucial for root formation. This means that the cuttings have to be inserted into a substrate that has a structure which is sufficiently open to allow air (containing oxygen) to reach the developing roots. Also essential are humidity and temperature. Humidity Cuttings without roots must receive the highest possible humidity. Humidity is highly influenced by temperature. When the first roots appear, the humidity can be lowered since the rooted cutting can assimilate better. Temperature To prevent excess transpiration, controlling the temperature is important. The soil temperature has a very direct influence on the speed of rooting. A soil temperature ranging between 20 and 25° is ideal during the initial rooting stage. After this initial stage, the temperature can be allowed to drop a few degrees. To reduce aerial growth somewhat, air temperature should be a bit lower than soil temperature. After all, the cuttings should be encouraged to use their energy mainly for developing roots. Aerial growth will come later.
	Rooting regulator Although cuttings sometimes form roots without receiving a treatment with a rooting regulator, the use of a rooting regulator is extremely valuable. With the proper use of these agents, cuttings will form better, more uniform roots in a shorter length of time. Speed is important; the faster roots develop, the sooner the cutting can absorb its own water. Uniformity is important to prevent any stragglers from slowing down the production process. ‘Better’ rooting means that the cutting forms roots all the way around the stem, covering several centimetres at the base instead of just forming a single root here and there. Only well-rooted cuttings can develop into top-quality plants.
	New methods To measure is to be sure To obtain the best possible growth from a plant, it is important to know what is going on in the plant at certain times. For this reason, it is advisable to use the proper instruments to measure the various processes in the plants. There are many sensors available for measuring the various processes in and around the plants. One of these, the tensiometer which measures the moisture in the soil, has been mentioned already. The CO2 level in the air is another measurable variable, just as is the amount of light reaching the plants. Even the amount of water flowing through a stem and the amount of CO2 absorbed by a plant can be measured. Computer models The data measured by the various sensors can be recorded with data-loggers, and the data from the data-loggers can then be read by the computer. This offers the possibility of keeping a very close eye on conditions during the various growth phases. Finally, a growth model can be developed for the purpose of controlling the entire production process. This way, every crop produces a uniform final product. Research Rhizopon, working together with growers and researchers all over the world, will continue its investigations in the coming decades. In doing so, we will be basing our work on the latest insights into plant physiology and making use of developments in electronic data gathering and processing.

Go to the Rhizopon Rooting Guide