These are methods of plant propagation where we don’t normally grow the plants from seed or it’s easier or more economical to propagate them using one of the above methods than growing them from seed. These methods also circumvent the inbreeding depression issue. In some cases plants can be propagated using more than one of the above methods, grapes are an example where they can respond equally well to layering, grafting and cutting depending on the growers objective.
Huge volumes of written material exist for each of these. The following is intended to make you aware of the subject, not become an authority on the subject. You should view the following information as a starting point for your own research.
Of the plants we grow (as in our personal garden, not the royal we) the ones we propagate by cuttings are potatoes, blueberry plants, rhubarb and horseradish. In tropical regions there are many plants used for food that can be propagated by cuttings but these are outside my knowledge base. There are also many ornamental plants that are propagated in this manner but being a non food plant they are outside the scope of this article.
With hardwood plants like blueberries success in rooting cuttings comes from understanding the types of stem cuttings. There are four and they are herbaceous, softwood, semi hardwood and hardwood. These terms represent the growth stage of the host plant material and is key to whether the cutting successfully roots.
Two of the stages, semi hardwood and hardwood are our focus for blueberries. Semi hardwood cuttings are taken from current years growth as it is nearing full maturity. This growth resists bending and breaks when stressed. The best time to make these cuttings is mid July to fall. Hardwood cuttings are taken from dormant, fully mature canes or stems. Hardwood cuttings are very firm, don’t bend much before they break. The time to make these cuttings is late fall through early spring. Most of the time we utilize semi hardwood cuttings because the environment is more moderate than in the dead of winter and we seem to have better success with cuttings that are a little more supple.
Before we continue I suppose I should mention the three types of cutting cuts, they are straight, mallet and heel. The most common is straight and it is just as its name implies, a straight cut across the stem. This is the cut we use in our blueberry cuttings and is the one you’ll be most likely to use.
A couple of general notes about propagation by cuttings is to make sure you select healthy, unstressed, disease free host plants. Try to avoid plants that you have recently fertilized. Also, make sure your cutting tool is sharp (razor sharp) and sterile to avoid the potential of spreading disease. A mixture of one part bleach to nine parts water is a good solution for sterilizing your cutting tool before you make cuttings. If you are not positively sure about your plant stock being disease free, dip your knife blade between every plant (preferably between every cutting) to avoid the potential of transmitting disease among and between plants.
For our blueberry plant propagation we take cuttings of semi hardwood from our plant about three or four inches long near the terminus of the cane. I like to select canes slightly smaller in diameter than a common pencil. If your cutting is carrying a load of leaves, strip off the lower leaves leaving only two or three at most. It is important to keep the cuttings moist until you have them in your rooting medium. I’ll generally use a damp towel folded over on a cookie sheet and slip the cuttings between the folds.
You’ll want to put your cuttings in a low fertility sterile medium with good drainage. I use one part masons sand (available at most any building supply), one part peat and one part perlite. I do take the time to bake the sand for around an hour at 200~300 degrees before I use it (be sure to let it cool before you use it) to ensure it’s sterile. I put this in trays three inches deep and wet it well. You should do all this prep before you take your cuttings.
The cuttings are then dipped in vitamin B12 (helps promote rooting, there are other rooting aids) and then placed about an inch to one and a half inches into the growing medium. If you make multiple cuttings from the same stem make sure you insert them the right way up (buds or leaves pointing up), and yes, this is a fairly common mistake with cuttings. The spacing between the cuttings should be far enough apart to allow sunlight to reach all the leaves of all the cuttings. Keep the cuttings and growing medium moist but not saturated. It’s better to mist them a couple times a day than to soak them every few days. If you can avoid having the cuttings in a high temperature area with 65~85 degrees F is about ideal.
Roots should begin to form anywhere from two weeks to two months depending on conditions. Once roots form we plant our rooted cutting in pots and up pot them a few times before we set them out. The largest we’ll go with up potting is one gallon pots. Don’t loose sight of the fact that blueberries are an excellent container plant to raise. In our experience you’ll want around a seven gallon planter at a minimum if you are going to container grow them. In extremely cold environs you may need to protect the pot from freezing conditions to avoid damage to the roots.
Cutting potatoes for seed pieces involves cutting the potato so there is at least a king eye on each piece. Personally I like to have at least three or four eyes on each seed piece. You can also grade your potatoes so you are using single drops as your seed. These are small potatoes around three quarters of an inch to two inches in size that are planted whole not cut, I lean towards single drops around an inch and a half in size when I use them. You cut seed pieces just prior (two or three days max) to planting. Probably the biggest mistake I see, when people are unsure of what they are doing, is to cut the seed pieces too small. You need to have enough potato to feed root and sprout growth and avoid having rot spoil the whole piece. Once you cut your seed pieces you need to leave them out to ‘skin over’ the cut. If you immediately plant your cut seed pieces you have a high potential for the seed piece to rot. You can use a material like Captan to coat your cut seed pieces and this is what I used back when I raised seed potatoes. It is not an organic control and it most likely will not be available after a collapse so it’s better if you just let your pieces skin over.
With rhubarb you need to carefully dig up the plant or a portion of the plant root. Clean most of the soil away from the root and then using a sharp knife split the crowns. These are readily recognizable as they will terminate in a bump at the top of the root ball. I generally try to encompass at least three crowns and a healthy portion of root for each cutting. Remove any portions of the root and crown that doesn’t look healthy. I let my cuttings skin over for about a day before I plant them.
Horseradish is very similar to rhubarb except you also have the option to make root cuttings as well as splitting the crowns. Root cuttings will be pieces of the side roots about six inches long about as thick as a pencil. I’ll be honest with you, I have better luck with splitting the crown than root cuttings.
Think raspberries and you have suckering in hand for most cane berries. Propagation with suckers is quite easy. Dig a sucker a safe distance from the main root of the plant (with raspberries I usually maintain a minimum distance of 14~ 20 inches). You can either bare root your suckers or keep some soil around them. If temperatures are high or the wind is blowing and you decide to bare root them, have a bucket of water close by to drop them into. I prune my sucker stock back to no more than 18 inches tall, then I dig it. Usually I maintain soil around the root, and in my garden as soon as I dig a sucker I plant it. It means a little more walking between source and planting rows but the transplants do much better the sooner they are stuck in the ground. I try to select suckers with canes between a quarter inch and half inch diameter for planting.
Just as with everything else, select the healthiest stock you have. I plant suckers in the early fall or late spring with early fall being my preference. Planting in the fall will give you quite a bit of jump over planting in the spring. There is an old gardeners adage for many perennials that goes, year one they sleep, year two they creep, year three they leap. Raspberries certainly follow this pattern. The first year you plant them most their energy will go to the root. They will send up a few primocanes. The second year they will send up more primocanes and you should notice a substantial amount of suckering going on. The third year you have a nearly mature planting that will require some maintenance but that is a topic for another article.
Layering is similar to suckering except the roots are usually forming on the opposite end of the cane. Marionberries are a perfect example of a good candidate for tip layering. In late summer cover a portion of the primocane near the end of the cane with a light covering of soil. It doesn’t need to be a very large area that you cover. The plant will start developing roots at the covered area. Once roots have formed you come along and cut the cane off behind the roots and you have a new rooted cane for starting a new plant. Our Marionberries are so aggressive in layering that I seldom have to bother with covering any of the cane to have some of them root and every year I have rooted canes I simply cut off and dispose of. If the stem of the plant species you want to layer is too stiff to lay along the soil you can use pieces of wire shaped as large staples to hold it down.
Plants like strawberries send out runners galore. At some point the runner will form a daughter plant. Often times the same runner will form more than one daughter plant. It is our practice to cut off all the daughter plants behind the first one. This increases the amount of energy it gets from the mother plant and helps keeps our beds from becoming overcrowded. Once the runner forms a daughter plant that develops roots, you cut off the runner and transplant the daughter plant. This is a very easy propagation method in that the grower doesn’t need to do anything until the new plant has formed. We usually let our plants overwinter and then plant the daughter plants in the early spring.
Grafting is a means of growing a desirable yield of one plant on the rootstock of another. Apples are a great example of this and I can remember as a youngster going to my grandfathers house and he had several varieties of apples all growing on the same tree. Grafting involves placing a scion (a healthy, dormant piece of the last years growth having from one to four buds on it) underneath the outer bark and into the cambium layer of another rootstock plant. In most cases spring is the best time to graft. There are several methods of grafting and tons of material that include diagrams available on the web so rather than duplicate that effort here I’ll let you use your favorite search engine to explore this topic more. Do take note of the fact that you can’t graft between different species, you need to graft apples to apples, pears to pears, grapes to grapes and so on, apples to pears won’t work. You are always welcome to hit me up in the comments section if you want.
I think that’s it for this installment.