What is rockwool?

• a mixture of “rocks” that is melted at high temperature to form a molten matrix, and then is passed across an air stream that cools the material and forms long fibrous strands that are bonded together to form slabs, blocks, plugs, etc., and granulates (non-bonded)
• General Hydroponics rockwool is mainly a mixture of basalt and dolomite (same constituents as Grodan made in Denmark)
• the material is chemically and biologically inert
• the rockwool is “clean” of any plant pathogens
• GH brand rockwool is produced using an electric melter which virtually eliminates pollution, versus the use of a coke-fired oven and is VERY BAD for the environment; also, the resin used to bond the fibers is a new technology from Canada which eliminates release of formaldehyde during the curing process making it a safer manufacturing process.

Rockwool is 97% (by volume) air (which means):
• you can control the air / water ratio in the substrate
• the greater volume of air will enhance root growth
• there will be less fluctuation in pH and EC compared with other growing mediums
• as water and nutrients drain from the rockwool or are taken up by plants, the “pores” of the material again are filled with air

Why use rockwool?
• >95% of the world’s greenhouse vegetable production is on rockwool!
• rapid rooting of cuttings and seeds and maximum yields
• allows optimum control of air / water ratio, pH and EC
• rockwool products come in a variety of shapes and sizesthat allow the grower to utilize it in many different types of hydroponic systems
• the most consistent production and highest yields in commercial production of vegetables occur on rockwool
• rockwool is a manufactured product so the material will be consistent; organic products, “natural” products and substrates that are simply dug from the ground will be much more variable

Advantages of using General Hydroponics (versus other brands):
• broader product line (BAB-12s, Chubby slabs, RP plugs, 50/50 granulate) than the competition
• new products always under development that can make your business more successful
• better prices and better quality make more money for you
• the only rockwool recommended for use with GH nutrients and the only rockwool with the GH name!
• made in North America using environmentally friendly technology
• Vibeke won’t show up at your store anymore!

• why is GH rockwool brown? Actually the rockwool is a yellow- green color but the new resin used to bond the fibers gives it the brown color. We here it’s made the Grodan people “brown with envy.”
• why are GH slabs heavier than Grodan? To keep costs low Grodan sells their “one year” Talent slab in the hobbyist market which is not their top-of-the-line product. The one year slabs tend to compress over time which reduces the amount of air and can lead to lower yields and sometimes even disease problems. GH sells only one kind of slab, which the commercial vegetable growers call a “multi- year” product. Even though it rarely is used for more than one crop the “multi-year” slab is denser and more durable and does notcompress and lose it’s air structure.
• why does Grodan push the vertical fiber slab? Originally the vertical fiber slab was developed as a gimmick to thwart another rockwool manufacturer that had a slab that drained faster than that of Grodan. The problem with this is that the water tends to run out of of the slab too fast, which forces the grower to irrigate more often than he would like and the roots just go straight to the bottom of the bag instead of spreading out. In Europe, where there are over 30,000 acres of hydroponic vegetables produced, growers prefer horizontal fiber slabs because it helps to develop a better root system.
• why does GH make both vertical and horizontal fiber slabs? We recognize the fact that many people growing in rockwool have never even seen a horizontal slab (thanks to Grodan!) so we will continue to produce vertical slabs for people who are comfortable with this. We will let our customers know as much information as possible about rockwool and then let them decide the product(s) they prefer.
• why does GH have products like the BAB and Chubby and the other rockwool manufacturers do not? General Hydroponics’ business is to provide superior technology to their customers. Grodan, as an example, only cares about their big commercial grower accounts and so they manufacture products for them, and if some of these products work for small growers and hobbyists, then fine, but they wont’ go out of their way to develop new products for our market. Conversely GH continually works on new products and innovations that benefit our industry.
• why do the Grodan people say that all of the world’s best growers use their product? Because they are not telling the truth! For many years they had the entire market alone but in recent years their competitors have taken away a significant portion of that. Examples: Leamington, Ontario: 600 acres: 25% on Grodan; BC Hothouse Growers: 250 acres: 10% on Grodan; Houweling USA: 60 acres: NO Grodan; Bonita Nurseries (AZ): 120 acres; NO Grodan. By the fall of 2000, their market share in North America is expected to decline by an additional 10%. If you want to buy based on reputation, why look anywhere other than GH?
• why do you make the Chubby slab? The Chubby was developed for two reasons: 1) to provide small growers a greater degree of flexi- bility when growing on slabs; and 2) the Chubby is one inch taller than a “regular” slab so it makes it even easier to maintain the “optimum” 60 / 40 water / air ratio in the slab.
• why do you make the BAB blocks? Ever heard of “bigger is better?” Just like the Chubby the BAB provides growers with more flexibility. It’s very tall, so it helps optimize the air / water ratio and also provides lots of rooting area. It can be used like a “mini-slab” by placing a plant (s) in a small block on top or directly transplant into it. It’s also adaptable to both ebb & flood and drip irrigation. And, it makes a joke of the Grodan DM10!
• why is GH rockwool an environmentally-friendly product? GH rockwool is made from basalt and dolomite, two natural constituents. Since the production process “spins” them into fibers composed mainly of air, our rockwool is an excellent amendment for garden soil. There actually are land-fills that allow deposit of used horticultural rockwool for free because mixing it with the other land- fill constituents helps to enhance activity of aerobic bacteria. Of course that’s only part of the story. Our manufacturing process utilizes two key methodologies that impart the environ- mentally-friendly “label”: 1) our electric melter uses hydro- electric power (no coal generation) and by melting the rock in this way (versus the traditional coke-fired oven) there is no sulfur given off in the production process; and 2) we use a resin to bond the fibers that does not give off free formaldehyde, which can be very dangerous to workers involved in production of bonded rockwool.

• what will the Grodan people say or do? If they’re smart they won’t say anything negative about GH but they definitely will do and say a number of things that they have done in the past that include:

-Vibeke will refer to it as the “brown wool”(which is kind of neat since GH rockwool really is brown!) to suggest to the customer that it’s just off-spec stuff compared to Grodan. ANSWER: Take a look at the product. Quality is as good or better than anything else on the market and the starting materials (basalt and dolomite) are the same as Grodan’s. And yeah, it’s brown because we use an environmentally friendly resin and they don’t!

-They will say that GH rockwool can’t possibly be as good as Grodan because the price is so much lower; they also will say that there is no way our prices will remain this low ANSWER: Unlike Grodan we don’t keep adding dozens of new people all over the world and using profits from one market to develop another. Our prices are lower than those of Grodan because our costs are lower (and always will be!).

-Vibeke will claim that a particular GH product “won’t work because of . . .” which she actually tried with the BAB blocks the first time she saw them (Grodan now says they will be coming out with their own BAB block!). ANSWER: Point out to the customer that people already are using the product successfully in the manner for which it is intended and in many cases the same or similar products are being used (under the Hydrogro® brand) by large commercial growers like Houweling in Camarillo, who grow on a form of the Chubby slab on 40 acres!

-They will tell the retailer that he can’t drop Grodan because they will loose the enormous strength of that brand. ANSWER: The GH brand is stronger in the hobbyist market than Grodan and in fact there is a distinct possibility that the GH name will help to expand the total market for rockwool!

-They will claim that Grodan is THE rockwool in the commercial market and that proves they are the best. ANSWER: Wrong! Take away Village Farms, which is owned by the same company that has a joint venture with Grodan in North America and they MIGHT be third! I really don’t think many people are too impressed when most of your commercial sales are to yourself! As noted in another part of this outline, Grodan people still live in the BC (Before Competition) time period.

-They will claim that their vast resources give them the ability to supply their customers with information that is not available from other manufacturers and that they have the “best” tech reps in the business. ANSWER: Wrong again! Yes, they have tech reps, but all they know is what the Grodan people in Denmark and Holland tell them. And in turn, where do those guys get their information? That’s right, the same place we do. From growers, university trials and other infor- mation in the public domain (isn’t the Web a wonderful thing?). We are in constant contact with growers, researchers and industry organizations around the world. We know more about rockwool than the Grodan guys because they just sell the stuff while we actually make our own products. As a little post-script, they do have the best paid tech reps in the business.

Handling rockwool:

-for a more complete description refer to Prof van Hydro’s 1-2-3 instructions
• before using any rockwool it must be “charged” with water or nutrient solution; the initial soaking of the product ensures that it will readily wick moisture on subsequent irrigations
• soak propagation plugs in plain water and rooting blocks in nutrient solution; there are people that claim rockwool has a high pH and must be pre-treated to make it lower, but that’s an old “wives’ tail” or perhaps the work of some marketing genius; if you are transplanting plugs into rooting blocks, it’s OK to soak the rooting block (prior to use) in nutrient solution; slabs always are charged with the same nutrient solution that will be used n ebb & flood or drip.
• rockwool is inert and as such you must be careful not to over-fertilize or over-dose with a pesticide because there is nothing to absorb and buffer the excess material; basicallywhatever you add to the rockwool is available to the plant; that of course can be both good and bad
• once a seedling is exhibiting a fair number of healthy roots it’s OK to start using a dilute nutrient solution with the rockwool
• prior to placing plants in an automated environment (ie., ebb & flood or drip system on a timer) irrigation and fertigation is a “touchy-feely” kind of thing; the tendency is to over- water but 36x40 mm propagation plugs in a room temperature environment under lights only need to be moistened every 2- 3 days until they are transplanted into rooting blocks
• just like GH nutrients, GH rockwool is a 1-2-3 system; start seed in 36x40 mm tapered plugs (TP3640) and cuttings in 36x40 mm round plugs (RPT3640 or RP3640); when lots of roots are evident transfer the plug into a rooting block (RB 4, 5, 6, 8 or 10); plants can be grown on the rooting blocks or, when they too have developed good roots transfer the rooting blocks onto a slab or a BAB.

The Product Line:
• PLUGS- anything used primarily to establish a seedling via seed or vegetative propagation is called a propagation plug. GH plugs may be tapered or round; singulated or in mats; and may be loose or in trays. The most common products people will be using are: TP3640 (tapered plugs in mats) and the RP3640 and RPT 3640 (round plugs loose and in trays, respectively). The TP3640 product is used primarily for germination of seed while the RP plugs are used for vege- tative propagation.
• ROOTING BLOCKS- this is the largest category mainly because there are so many different types and sizes of systems in the hobbyist market that it requires many different blocks. The main products that customers will use will be: RB 4 (3” block); RB 6 (4” block); and the BAB-12 (the really BIG block). BABs don’t come with holes but the RB 4 and RB6 products come with- or without a 4240 hole that accomodates 3640 tapered and round plugs as well as RB4040 (miniblock) blocks. Refer to the product code sheetfor all of the sizes and dimensions, as well as the other block products not mentioned here. Our competitors don’t have a BAB block!
• GROWING SLABS- slabs are used commercially with drip irrigation systems but many hobbyists also used them in ebb & flood (refer to primer on potential plant problems growing on rockwool). Plants are rooted in plugs after which plugs are transplanted into blocks where they grow for 7-10 days and when roots begin to penetrate the grooves in the bottom of the blocks they are transplanted onto slabs (see 1-2-3 instructions for details of the process). GH currently has two basic types of slabs: the “standard” slabs are either 15 or 20 cm wide, 7.5 cm tall and either 90 or 100 cm long and wrapped in a poly bag (black inside / white out- side). The other type is the Chubby, whose dimensions are 25 cm wide, 10 cm tall and 45 cm long (also wrapped). All slabs carry the code “GS” for “growing slab.” The first type of slab also can come in either a “vertical” or “horizontal” fiber orientation. Please see the “Why?” section of this guide for a bit of background on this concept. At this time, GH is the only brand with a Chubby slab, which because of its dimensions, is perfect for hobbyists who need flexibility in spacing and desire the positive benefits of a “taller” slab. We hope to introduce 10 cm tall 90 and 100 cm-long slabs by the end of the year.
• GRANULATED ROCKWOOL- granulated rockwool does not have the resin used to “bond” the plugs, blocks and slabs. This so-called “loose wool” can be used alone or combined with other growing mediums to modify air- and water-holding characteristics. GH offers three types: absorbent; repellant; and a 50/50 mixture of each. The product comes in a 20 kg bale, compressed that provides approx. 14 cubic feet of material. GH is the only brand that provides the compressed 50/50 combination, which is a sought-after product by hobbyists.When things go wrong- a primer for problems with plants grown on rockwool
• During the production process a wetting agent is added to the fiber that helps make it “wet up” more rapidly. If someone calls and says they have blocks that float for hours without submerging in a bucket of water, it means they don’t have enough wetting agent in them. Solution: add about 50 ppm of an agriculturally approved wetting agent to the water and the blocks will soak it up. This is a rare occurrence but if a customer gets “floaters,” this is the cause.
• Someone’s EC was running high and they leached the system with clean water and the plants started looking REALLY bad. They should have immediately changed the solution in their nutrient tank and used that solution to leach the slabs or blocks rather than the “clean” water. Unlike substrates where the nutrient solution quickly flows out and is added on a more frequent basis, nutrient solution slowly drains from the rock- wool matrix, so adding “clean” water temporarily throws off the pH and EC even more. By adding the correct concentra- tion of nutrient solution it will help “equilibrate” the system.
• Seedlings in propagation plugs “damped off” and the customer thinks the rockwool killed them. No, possibly the seedlings were over-watered, but since rockwool is inert and pathogen-free, they either had a “dirty” growing area or they watered so much that the roots “suffocated” from lack of oxygen.
• The so-called “slab and block” rockwool system was developed for use with drip irrigation. Unfortunately slabs are used quite often by hobbyists with ebb & flood, and so many of them tend to keep the rockwool too wet. This is where the Chubby slab can be very helpful because the extra height helps keep it “drier” even in ebb & flood. Basically, if someone is using ebb & flood with slabs, they should change their irrigation scheduling so that they irrigate more frequently but cut back on the flooding periodby about 20% (eg., instead of flooding 3 times per day for 15 minutes at a time, flood 5 times per day for 10-12 minutes).
• Rockwool is such a good growing medium that there aren’t that many problems associated with it.