There is much more to the propagation of cuttings than just getting roots to form. IT'S ALL ABOUT ENERGY (CARBOHYDRATES). If you start with week cuttings that contain little energy, problems will abound. Do not skimp on quality of the ingredients for the rooting medium. Oxygen is necessary for root respiration at all times, but oxygen plays an even more critical role in the initiation of new roots on a cutting. For rooting of cuttings, drainable pore space in the medium should be 45% to 50%. Once the cuttings has rooted and are to be transplanted to grow on, the drainable pore space in the medium in a one or three gallon container should be about 20% to 25%. Keep temperatures in the propagation area in the range of 75-F to 100-F. Cells cannot function and divide without energy. Energy for initial root production must come from the parent plant and already be present in the cutting to be selected. But, as soon as the first new root is little more than a bump on the base of the cutting, it can begin absorbing nutrients and support leaf functions and accelerate energy production. Provide nutrition, light, and other growing conditions favorable for the plant from the time cuttings are stuck. If you provide nutrients (272-grams 18-6-12 Osmocote (NO EXCEPTIONS), and 49 grams good trace mineral mix such as STEM per cubic foot of propagation medium) light, water, space, etc. to cuttings they will respond much more rapidly than you are likely to expect. Osmocote 18-6-12 more nearly coincides with the root development of the cutting and stimulates the subsequent growth of nearly all species if some other factor is not restricting growth. Root zone aeration is much better in deeper containers, therefore, use NO container with a depth less than 3.5 inches. The dissolved minerals in the water used to mist cuttings can have a PROFOUND influence on rooting and subsequent growth. High sodium and high bicarbonates are the most common culprits. In general, the lower the mineral content of the misting water, the better cuttings root. Timely transplanting into larger containers to grow on is very important. Transplant just as soon as the cutting has sufficient roots to hold the mass together. A little early is better than being late. It is important to keep a thin film on water over the surface of the cuttings and high humidity in order to prevent desiccation of plant tissues that have lost the support of roots, until new roots form.
When to take cuttings is a perpetual challenge to the propagator. This is truly the "art" of plant propagation. Keep in mind that energy levels in plant tissue typical reach a maximum in late summer or early fall. This energy level changes only slightly during winter. However, with the first flush of growth in the spring, The energy level drops ABRUPTLY. This is because the energy was spent in support of the expanding bud and new growth and with some species like citrus, development of flowers and fruits. With citrus species that make several flushes of growth, the buildup of energy progresses, then drops again with the next flush and so on. The key to cutting propagation is to wait until the energy level in the tissue has recovered to a higher level to support root development, yet not wait too long and lose the responsiveness and ability of young tissues to produce roots. Also keep in mind that a time period typically can be 30 to 60 days to root most broad-leaf cuttings. If cutting are taken too late in the fall and early winter season and the bud chilling requirements has already been met in the cutting, as soon as the cuttings are placed in a warm cutting area, buds swell and new growth begins and energy levels drop leaving little to support root initiation and growth. In general, it has been found that there is no ideal rooting medium but several combinations of materials can provide a good, workable medium with a drainable pore space of 40% to 50%. Good quality peat and coarse perlite or peat and ground pine bark on a 1:1 or 1:1.5 or 1:2 basis by VOLUME works well in propagation containers approximately 3.5 to 4 inches deep. I have found on a variety of occasions that bags of "coarse" perlite were far from being coarse. It is VERY VERY VERY important that the components of the rooting medium are free of diseases and insects. Perlite is sterile when purchased. GOOD quality peat moss, although not sterile, is clean and ready for use directly from the bale and has some capacity to suppress pathogens. By contrast, ground bark can range from relatively clean to unacceptable containing soil, pathogens and weed seeds. DO NOT - I REPEAT DO NOT - cut corners with respect to the rooting medium, as it is false prosperity. The size and type of cutting to be taken are sometimes dictated by the size and vigor of the branches on the parent plant. In general, however, cuttings should be four to seven inches long and medium to large in stem diameter for the species or cultivar. Slender branches, and all branches from the shaded portions of the parent plant should be avoided since they are lower in carbohydrates and less likely to root and become vigorous plants. The leaves on the cutting play a very important role in rooting. Leave one or two leaves on the cutting.
REMEMBER the condition of the parent plant supplying the cutting is very important. In general, the more vigorous and healthy the parent, the better the cuttings root and grow as long as they are not overly succulent. Good luck. Thanks for being a member of this forum. - Millet