A lot of people have trouble with clones in rockwool until they have done a few batches. Here's a photoessay on a batch of clones as they are done around here. One of the biggest problems with rockwool cubes is that they can hold a LOT of water. If cubes are too wet, rooting will be slow or stem rot may set in. Think damp, never wet or saturated. A dry 40mm cube weighs 5g. A properly "damp" cube weighs 25-30g. Heavier than that is too wet. Remove water from overwet cubes by shaking excess out into a bucket with a snap of the wrist. A salad spinner is great for draining cubes after pre-soaking, without giving yourself 'tennis elbow.' Rockwool cubes must never be squeezed- removes airspaces. Since I grow SoG style, I cut very tall clones. Taller clones become taller plants faster- important in SoG as no vegging time is given to clones before they are flowered. As soon as they have a good set of roots, they go in to the flowering area. My clones are too tall to fit in a humidome, but humidomes usually keep things TOO humid anyway, especially when using rockwool cubes on a heatmat. Clones do best in a controlled environment, so I built a clonebox with 3x twin 18W fluoros (on 24/7), a fixed-temp (30C) heat mat and a thermostatically controlled exhaust fan. The ballasts on the fluoro lights put a fair amount of heat into the box air. When the temp comes up to 26.5C, the fan kicks on. So, here we go! First, sterilise all plant contact surfaces (trays, inside of clonebox) with a 10% bleach in warm water solution. 1-2 drops of dishwashing soap helps make the cleaning solution "wetter," assuring every little nook and cranny is germ-free. Rinse and allow to dry. Don't forget to wash your hands thoroughly with the same solution- use a fingernail brush. These mother plants are about 6 weeks old. They've donated about 3 sets of cuttings and will be replaced with one of their 'kids' soon. Note that these are only two of my mothers. I keep 8-10 mothers to support donation of 30 cuttings every 15 days. Mothers are vegged under a 400 HPS (soon to be a metal halide). Rockwool cubes are first rinsed well under running tap water then pre-soaked in a bucket of pH5.0 water for 24 hours. All the pre-soak water is removed with a salad spinner. Immediately before plugging in cuttings, cubes are each given about 25ml of a clone watering solution made from: * 9-10L tapwater * 9-10ml H2O2 (50% horticutural grade) * pH adjust as needed to 5.8 (correct pH last) The nutrient is not entirely necessary- a plant without roots can't assimilate nutrients, only water- but nutes in the clone watering solution assures nutes are available to the plant as soon as it has formed root nodes. This gets nutes to the plant a day or two before you actually see the roots out of the bottoms of the cubes. Well developed mothers in good condition will have a couple of weeks worth of nutes stored in the leaves- and so will the clones you take from them. A well developed mother plant about 4 weeks old. Has donated about two passes of cuttings. Sterilise the scalpel blade by dipping in methylated spirit (aka denatured alcohol) before and between making cuts I cut BIG clones. Stem length is about 9". Cut the biggest diameter stems you can get for clones. This is how they look when just cut off the mother. Make the stem cut at an angle, about 45 degrees. Cut off all the branching until you have something like this. Split the end of the stem. Disrupted cells on the stem more easily become root nodes. Gently scrape the last 25mm (1") of the stem in a few places with the back of the scalpel blade. Dip the stem in rooting powder. Gently knock off any excess; only a dusting is needed. Powders work better than gels because they form a paste which stays put through several waterings. Gels can support pathogen growth in between batches. If you use gels, put a few ml in a small container and dip stems into that gel- not in the main container. Discard any excess. Even opening the gel container will admit a few pathogens. Once opened, keep gels in the refrigerator. Plug the stem into the cube, using care not to poke through the bottom of the cube. It is important that the rockwool fits tightly around the stem. Some cubes are not very dense in some parts of the cube. Test the density of the rockwool by touch and plug the stem in the densest part of the material. Some cubes collapse when you try to plug a stem in them. Discard cubes like this. The air gap between the stem and cube will prevent proper rooting. Clone #1 done! Big clones work better in Sea of Green. There's no veg time given to clones in SoG before flowering. Bigger clones make bigger budstalks. As you see, these are about 9" tall. Now, let's prune back the mothers. Some stems are too small to make cuttings with on this pass. We'll take cuttings from these stems when they have developed more in about 2 weeks. Snip off the growing tip to force growth to divide. Leave the leaves and the following nodes- these sites will develop into cloneable branches on the next pass of cuts in 2 weeks. Mother plant pruning detail. Growing tips gone but the next nodes down are not disturbed. Mother plant pruned and ready to go back in & veg for 2 weeks until the next batch of cuttings is needed. "Before" pic repeated here for comparison. A freshly done batch of clones in the clonebox. Roots pop on day 6-7. Roots on day 8. 21/30 strikes on day 10. And here we are on day 10. No yellow leaves! Yellowing leaves are a sign of excessively high air temp or overwatering. Cubes in the left-hand tray have not set root just yet. I only need 20-21 clones per flowering batch. Extras become mother plants- or compost! The clonebox conditions and getting the watering right are EVERYTHING. Quick rooting with the plants in best shape is dependent upon several things; I consider a heatmat to be an essential. Thermostatic control of air temp makes striking time reliably 6-7 days, every time.