Garden Word of the Day
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“I can give you a cutting of that, of you like.”
Well, what are cuttings and why would you want one?
Most of us have seen how the leaf of a Jade plant (Carassula argontea) can be plucked from a parent plant, stuck in some soil, and the leaf becomes an independent plant. Cuttings can be from leaves, roots, or stems. Before we learn about each of these propagation methods, let’s find out how a piece of a plant can become a whole plant.
How do cuttings work?
Being able to produce a new plant from a piece that was cut off is due to two conditions called totiopotency and dedifferentiation. Dedifferentiation means a specialized cell can return to a state of undifferentiated, meristem tissue, which can then become any other cell found within that plant. Totiopotency, or cell potency, means that every cell contains all of the genetic information needed to generate the entire plant, much like the supreme personage of Element Five movie fame. This means that, in theory, a single cell can be used to regenerate a new, identical plant. Of course, outside of the lab, your chances of success are much higher if you have many, many cells to work with. Let’s see how the different methods of cuttings can be used to propagate your plants.
The Jade plant mentioned above is an example of a leaf cutting. In that case, new roots, and then new stems, are formed at the wound site, after it has had a chance to dry a little. Most plants cannot be generated from leaf cuttings. While a few spindly roots may appear, they quickly rot and die. Leaf cuttings are best suited to succulents, cacti, and a handful of popular tropical houseplants. These plants can form new roots at the base of the petiole, or leaf stem, from the axillary (or lateral) bud, or from the leaf veins. There are four types of leaf cutting:
There are three basic types of stem cuttings: herbaceous, softwood, and hardwood. Brand new growth is “green” or herbaceous, softwood is slightly more mature, and hardwood is woody and fully mature. [This is not the same thing as hardwood and softwood trees.] Hardwood is the most difficult to propagate with cuttings. Some plants, such as mint, seem to spread whether you want them to or not. Very often, these plants are well-suited to propagation by stem cuttings.
Herbaceous stem cuttings are taken in spring. Make sure that your stem cutting contains both nodes (where leaves and buds occur) and internodes (the spaces between nodes), since some plants generate roots at one, while others root at the other. If you have both, it won’t matter. Tomatoes, basil, sage, and many other herbaceous plants can be propagated this way.
Hardwood cuttings are taken from fig, grapes, pomegranates, quince, blueberries, mulberries, some plum varieties, currants, kiwifruit, and gooseberries, while they are dormant. There are three types of hardwood cutting: straight, heeled, and mallet. Straight hardwood cuttings are simply 6 to 15 inch segments cut from near the end of pencil-width, one-year old branches, using a flat cut, removing any unripened green growth from the terminal end using an angled cut. [There is not enough food in the growing tip to be useful.]
At the proximal, flat-cut end, remove some of the outer bark, exposing a little of the cambium layer (light green). If you are using rooting powder, do so at this time by dipping the exposed area in the powder, tapping the branch gently to knock off the excess, and then insert the stem in a hole created with a dibber (or a pencil). This prevents the rooting powder from being scraped off. The stem should be submerged in the rooting medium, leaving only the top bud above soil level. Mallet and heel cuts are used for the most difficult to propagate plants. Heel cuts include a portion of the parent branch, while mallet cuts include small segments from the parent branch.
Softwood cuttings are more likely to succeed when taken in mid-summer. Softwood plants include perennials, such as blueberries, rosemary, thyme, sage, oregano, lavender, lemon balm, as well as some ground covers, vines, shrubs and trees.
You know how amazing it is that roots always know to go down and stems tend to go up? Well, when you take a stem cutting, the bud that was closest the parent plant’s center (proximal end) will become the roots, while the end that was farthest away (distal end) will become stem tissue. This is due to a behavior called polarity, caused by auxins within the stem. (Auxins are plant hormones.) Simply turning them upside down does not change this behavior, so plant accordingly. Also, because buds contain the auxins needed to stimulate root and stem growth, make sure there are buds on your stem cuttings, and that the area around the bud is not damaged. If there are any leaves present, let them stay, as long as they are not too big. Leaves are a source of auxins and other cofactors used to stimulate root development, as well as food through photosynthesis. If the leaves are too large, they can be trimmed down with a pair of scissors.
Many people mistake the spreading habit of plants produced by stolons and rhizomes as a form of propagation by cuttings, but this is not accurate. Those plants produce roots and stems at broken points as a natural growth behavior. Root cuttings, on the other hand, produce new stems and roots at the pericycle, which is the area between the epidermis and the phloem, near the cambium layer. Adventitious roots are more likely to occur when root cuttings are taken from juvenile plants than from older plants. Plants propagated from root cuttings may exhibit new characteristics (phenotype) due to normal genetic behaviors of different layers of cells (periclinal chimera). In English, this means that root cuttings taken from a thornless blackberry will produce blackberry bushes with thorns.
Large rooted plants - Root cuttings are generally take from 2 and 3 year old plants during the dormant season. To help you remember which end of the root is the top, make the upper cut horizontal, while the lower cut is angled. You will need a segment that is 2 to 6 inches long. Store your root cutting in moist peat moss, sand, or sawdust at 40°F for 3 weeks. Then, insert the entire root cutting into the medium, with the flat, top edge level with the rooting medium. (horseradish)
Small rooted plants - You will only need 1 or 2 inch sections of these roots for cuttings. Then, simply lay them on the rooting medium, about 1/2 an inch deep. (geranium, bleeding heart ming aralia)
Plants are classified according to their rooting ability: rapid rooting, auxin-requiring, or cofactor-deficient. Rapid rooting plants have everything they need and will begin rooting right away. Auxin-requiring plants need help from a root compound that contains, you guessed it, auxins. Some plants contain root inhibitors and they lack the rooting cofactors. Simply applying rooting hormone will not help.These plants are really tough to grow from cuttings.
There are many factors that have an impact on whether or not your cuttings will survive and thrive. These factors include environmental conditions, the physiological state of the plant cutting, and the rooting media or soil.
Since each plant has its own Perfect World, you will have to research each species individually, but they are all more likely to succeed when cuttings are taken first thing in the morning.
How to take a cutting
To ensure your cuttings can survive the process, always use a very sharp knife or razor that has been sterilized in rubbing alcohol. This will prevent the spread of disease to the cutting. Tearing or using shears to remove cuttings does not leave a smooth edge and plants tend to be unable to heal quickly enough to start growing. Remove any existing flowers and flower buds. If leaves are particularly large, they can be reduced in size to allow for better air flow while still allowing photosynthesis to occur. To speed the rooting process, you can dip the cut end in rooting powder, which may or may not contain a fungicide.
Cuttings can be an excellent way of continuing the line of a preferred plant without spending any money.
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