Growool is water absorbent rockwool made in Australia and is used as a soiless growing medium. Growool consists of a mat of long, fine fibres, spun from natural molten rock. This mat is cut and shaped by Growool Horticultural Systems into the individual Growool products. When using the Growool system there is potential for greater control over plant growth and yield. These potential advantages are only realised with very good management and attention to detail. Soiless systems do not guarantee success. They require better management than soil based systems. Your system must be set up carefully and then monitored closely and accurately. Plants and nutrient solutions must be checked carefully and regularly. Properties of Growool Growool has a unique combination of properties which make it an excellent growing medium. These properties need to be considered if the material is to be used to its maximum effectiveness:
Its rigid shape makes it very easy to handle.
It is inorganic and inert ie contains no nutrient.
It has no cation exchange capacity ie it won't bind nutrients.
It has no pH buffer of water or liquid feed.
It is a natural rock and is not biodegradable.
It has very high water and air holding capacity, typically 80% water plus 17% air. This is influenced by the height of the growool and the drainage characteristics of the surface upon which it stands. The deeper the slab the better it drains and Growool should always be able to drain freely. Growool Products The Growool system is an integrated product which starts with the Growool Propagation Blocks. These blocks are used to strike cuttings or germinate seeds. Once a small plant is established in the propagation block ,the block and plant is transplanted into a wrapped cube and left to grow until root hairs begin to appear at the base of the block. At this time the Growool slabs are laid out, and the cubes are 'planted' onto the slabs. For continued growth, in the commercial application, each plant is fed water and nutrient through a dripper. The home hobbyist often sets his slabs in a flood and drain system. The basic rockwool systems used in Australia are similar to those used in Europe. At the Hydro Shop we recommend that you use the Growth Technology Europonic Grow and Bloom formula nutrients. These nutrients are specially formulated to be used in Growool Systems. Oz Can is another excellent nutrient to be used in growool. Hygiene Growool is sterile when packed but, as with soil based systems, disease can be introduced unless rigorous hygiene precautions are taken. Seeds, cuttings, water, cloning materials etc must be all free from disease while the growing area should be disinfected before the system is established. Covering the ground with a polythene sheet before laying out slabs will reduce disease and infection. Maintain hygienic management throughout the life of the crop. Initial Wetting Because of the manufacturing process Growool, when wetted for the first time, has a slight pH change. This is a one off reaction. It is recommended when first using Growool cubes, blocks and slabs that you soak them in a Nutrient Solution adjusted prior to soaking to about 5.2 pH. Allow the Growool to soak several hours in this solution prior to using. This will ensure excellent results every time you use Growool. This compensating reaction will be complete in several hours and then run your nutrient level at the desired pH for the remaining life of the Growool. Growing in the Rockwool System
Plants which are raised from seeds or cuttings in propagating blocks should be transplanted into wrapped cubes with holes as soon as roots appear. Thoroughly wet the propagating blocks and the wrapped cubes with a complete nutrient solution before transplanting. The wrapped cubes are easy to wet by immersion in a bucket or tank of nutrient solution.
Remember instructions with regard to initial pH shift see notes above. To separate propagating blocks split off a long row of blocks from the sheet, then tear off individual blocks and insert them into the hole of the wrapped cube. Space out the wrapped cubes in trays or on polythene sheeting. Do not allow stagnant nutrient solution to accumulate around the base of cubes. Growool should be free draining at all times. Most plants will benefit from standing on a thin layer of expanded clay to improve drainage.
Plants which have been transplanted into wrapped cubes should be fed using full strength nutrient. A simple test of whether liquid feeding is needed, is to check the weight of the wrapped cubes to ensure they are not becoming too light. When root hairs are beginning to appear at the bottom of the wrapped cubes it is time to transplant the wrapped cubes onto wrapped slabs. Saturate the slabs with nutrient by cutting holes in the plastic covering. Take care to slit these holes in the plastic along the bottom of the wrapped slabs. Again remember the pH instructions for initial wetting. A lot of nutrient solution is needed for each slab (approx 16 litres) and is best applied using a siphon hose direct from the nutrient tank. Planting involves placing wrapped cubes at appropriate spacings on the upper surface of the slab. With a single edged razor blade cut holes in covering plastic so that roots protruding from the wrapped cube comes into direct contact with Growool fibres on the wrapped slab. This is a simple procedure as you will use the outside shape of the wrapped cube as a template to cut a hole in the plastic of the wrapped slab. At this stage you may also cut the plastic from the bottom of the wrapped slab. you should leave an overhang similar to a fitted sheet. This prevents the plastic coming loose during the life of the slab.
The plastic is covering the slab to prevent algal growth and reduce evaporation of the nutrient from the slab surface. In the first few days after laying out cubes on your slab dribble nutrient through the cube to ensure plant receives adequate nutrition. When the roots penetrate the slab you can then begin operating your flood and drain table. Managing the Crop Plants on slabs should be fed with Nutrient Solution constantly. The pH and Electrical Conductivity (E.C.) of the nutrient solution must be controlled and adjusted. As a general rule the should be pH 6.0 - 6.5 and 2.0 - 2.5 Milli Siemens respectively. Feeding and watering is best done on the principle of "little and often' It is safest not to allow the slabs to dry out too much. A properly managed system is worked around monitoring the nutrient solution available to the plants. This require regular sampling of the solution in the slabs. Use a syringe to extract a sample of the liquid and test for pH and E.C. The Hydro Shop sells simple meters which test for pH or E.C. Other than watering and feeding, the management of crops grown in Growool systems is identical with those grown in other horticultural systems. When the crop is finished stop watering the crop. Plants will use up all the water/ liquid feed in the Growool and will wilt and finally dry out. Dispose of used Growool thoughtfully. Please note it is an inert material and will not compost or rot away.
