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Propagation and Early Vegetative Growth Introduction Propagation is the term used to describe the way in which plants re-produce themselves. There are basically two ways in which this is done. Through cloning, this re-produces plants genetically identical to its parent and by sexual reproduction which produces seeds that are a genetic mix of both its parents. Cloning is often used by growers because it produces numerous identical plants that have known characteristics, i.e., flowering time, growth patterns, taste, colour etc. with little or no variation in quality. This is advantageous to the grower because they can tailor the growing conditions to the particular variety. Although there are many different ways to clone plants, including grafting and tissue culture, taking cuttings is the most widely used due to its simplicity. Some varieties of plant suit different methods, but in general, most plants can be propagated by taking cuttings. Cuttings Methodology Taking cuttings has a reputation for being complicated and unreliable, but in actual fact, following a few simple rules you can achieve good results every time with a low failure rate. By careful attention to the growing conditions it can become a simple and reliable process. Essentially a cutting is taken from the last 3-4 inches of a plant, including the growing tip. The stem is cut at a 45 degree angle just below a leaf node (where the leaf stem joins the plant). The lower set of leaves are trimmed off, leaving the tip and 1 or 2 sets of leaves and dipped into root hormone gel such as Clonex. The stem is then quickly inserted into the growing medium, such as rockwool cubes. The stem should be about 1/2-1 inch deep. Speed is important to avoid air bubbles in the stem base, this can slow or halt the rooting process. Some people recommend making a second cut, under water to avoid this problem but in practice this is not always necessary. The cuttings are then put in a under a fairly weak, cool fluorescent light initially to avoid stressing the plant too much before roots have started to grow. This normally takes 1-2 weeks depending on plant variety and root medium temperature. To keep the humidity at the correct level for rooting a lid is often put over the cuttings. Ideally a plastic heated or unheated propagation tray is used. Water the medium regularly. If it dries out, the cutting will die instantly. With regular watering, misting and bottom heat, small white roots will soon be seen coming out the bottom of the cubes. They are then ready for transplanting and a more intense level of light. Equipment Needed; i) Original Stock A good healthy plant in its vegetative phase is essential. A weak plant or one that’s starting to flower will take ages, if ever, to root. ii) Growing Medium Many mediums are good for rooting as long as they have good aeration and are not too cold. Rockwool is the preferred medium for most growers because of its simplicity and sterile nature. If rockwool is used, care must be taken to soak the cubes in a WEAK nutrient solution (about 1/8 strength) for at least a couple of hours and Ph down applied to counteract the alkaline nature of rockwool. A Ph of 5.8-6.3 is about right. Small rockwool propagation cubes are available with a hole already made to insert the stem into. They come in trays that make moving simple matter. Rockwool is also good because of its high aeration. It is possible to drown the growing roots in other mediums if too wet. iii) Fluorescent Lighting Until the cuttings have a root system to deal with a lot of light, the ideal lights are fluorescent type lights that bathe them with a bluish-white light without a lot of heat being generated, which can dry the cuttings out. The Nebula and Lightwing fluorescent lights are ideal for this. They are left on 18-24 hours a day. iv) Heatmats and Heated Propagation trays These heat the rooting medium slightly to speed the rooting process. The trays also have a clear lid to keep the humidity high and stop the cuttings from drying out. It is a good idea to lift the lid on the propagation tray every day or two to let any excess moisture escape and replenish the air. (v) Hormone rooting solution - Clonex This encourages rooting and often includes anti-fungal to stop wilt. (vi) Sterile blades These are useful to ensure a clean cut with no contamination (vii) Misters These are used again to keep the humidity high, although care must be taken not to over do it. If the cuttings are in a heated and covered propagation tray these may not always be necessary. There are also various products to prevent the cuttings from drying out if wilting becomes a problem. Normally though, the cuttings will wilt a little for a couple or three days until the roots start to grow and the plant can start transpiring properly. Most Common Problems; Root medium too cold. Too dry (Normally due to heat from the light) Seeds Methodology Seeds can be sowed into soil, directly into rockwool cubes or most other growing mediums. Again soak any rockwool used in a weak Ph adjusted solution. (See above) In soil, they should not be sown too close together to avoid spindly seedlings, a couple of inches apart is ideal. The seeds should be about half an inch below the surface and at least 2 inches apart to avoid the plants 'running' and their roots getting intertwined, which makes transplanting them more difficult. Again it’s good to keep soil temperature warm and moist. After a week or two most should have appeared above the surface and are ready to be transplanted into their final growing place, carefully! Be careful not to damage the root system. The smaller less vigorous plants can be destroyed as they often don't ever catch the others up. Again it is important to never let the medium dry out as it will kill the seedling very quickly. The medium should be moist but never wet as this can drown them. Again a propagation tray and lid will do the job nicely. While waiting for them to surface a mister is often a better way to wet the soil as it doesn’t disturb the soil and avoids over watering. Light-wise, they seedlings can handle a little more light than cuttings as they already have a rudimentary root system when they surface. They generally are a lot more vigorous than cuttings and grow a lot faster. Until they have developed from this juvenile stage they are will not flower, unlike cuttings that are mini-adults and can be induced to flower straight away. (Which is of obvious benefit if looking for small flowering plants.) Growing On - Early Vegetative Growth Light Source There are several specially made lights suitable for rooting cuttings and seedlings. Until they are well established, fluorescents are usually used because of their light spectrum and cool temperatures. These can be placed a few inches away from the plants and will encourage stocky and healthy growth. At least 18 hours of light per day is needed and as much as 24 hours is usual. As soon as they are established they can be swapped for the higher output HID lights, which must be placed a further away (2-3 feet) because of their higher radiant heat output. Metal Halide are the preferred lights for vegetative growth at this stage, (Blue light stimulates root growth with short internodal length), Metal Halide conversion bulbs that run on HPS ballast are also available. Environmental Conditions An ambient temperatures should be about 65 - 80 degrees is suitable for seedlings and cuttings, although the root temperature should be kept at the upper limit. This is normally regulated by the heated propagating tray or heat mat. Until well established, keep the humidity high, (above 80%) to keep the cuttings from drying out. Seedlings can handle slightly drier conditions. As soon as they are rooted and growing, the humidity should be reduced to normal growing levels. (<75%) |
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