Plant propagation

  • Published: Monday, March 2, 2020

Part 1

Occasionally, someone calls me with a question about propagating a plant that they really like. Can they save seeds and plant them? Or should they try cuttings or grafting?

Some plants are easy to propagate and may have several alternative methods. Some are more difficult and may have an optimal way of propagation, with very specific steps. So in my next few columns, I thought I would introduce you to the world of plant propagation.

Before I start, let me give one caution. Be sure that it is legal to propagate your plant before you try. Some plant cultivars are protected by patents, and propagating them, even for home use, is illegal.

There are two basic ways that plants can be propagated: seeds and vegetative propagation. This week, I will cover seed propagation.

In many ways, propagation by seeds is the easiest. However, some species do not produce viable seeds. In addition, other plants produce seeds that may not produce true-to-type offspring. In those cases, vegetative propagation may be your solution.

What do I mean by “true-to-type”? Seeds are the end products of properly pollinated and fertilized flowers. If all goes well, these flowers will eventually produce a viable seed.

Some plants have flowers that are self-pollinated. These are usually safe to save seed from and will result in offspring that are the same type as the parent.

However, some plants must be cross-pollinated by a different cultivar of the same species. When this occurs, there is a mixing of genes. This will result in an offspring that has traits from both parents. Thus, the offspring may not be the same type as the parent plant you were interested in propagating. Apples provide a good example of this.

Hybrid plants are another example where saving seed is not a good idea. These plants are the products of two inbred lines of parent plants, and while the initial cross (the F1 generation) produces uniform plants, the seeds produced by those plants are not genetically stable. That means that offspring from those plants probably will not be true-to-type. If the plant that you want to propagate from seed passes all the above tests, and is not patented, then you have an excellent candidate to save seed from. You may need to take special measures to ensure that cross-pollination does not occur in order to keep everything true-to-type.

Also, be sure that the seed is mature. Seeds from green peppers, for example, usually do not germinate well. You need the pepper to color up and be mature, perhaps to the point of being over-ripe, for the seed to have good germination.

Many seeds are dormant when first produced by the plant, and will need special treatment to germinate. Some, for example, need a period of chilling before they will germinate. Others may have a thick seed coat, which must be broken so that they can absorb water and germinate.

In my next column, I will discuss vegetative propagation, sometimes referred to as cloning.

Part 2

In my last column, I started a series on plant propagation, discussing seed production. This week I will cover some of the methods of vegetative propagation, sometimes referred to as cloning.

The reason we refer to them as “clones” is that they are exact genetic copies of the plant you are trying to reproduce. This is especially useful for plants that do not produce viable seeds. It also usually results in a mature plant more quickly than growing from seeds.

I will be describing several methods of vegetative propagation, but remember that not all plants can be propagated using any method. Experience has shown that some methods work better than others for a given plant.

The first method I will mention is using cuttings. Here you are taking part of the plant, and inducing roots to form. Typically leaves, stem tips, buds or stems are used. Stem tips are perhaps the easiest. With this method, the end of the stem, including the terminal bud, along with a few leaves is used. The stem should be 3-4 inches. Remove the leaves most distant from the terminal bud, making sure at least a few leaves are left. Then dip the end where the roots will grow in rooting compound, which is a plant hormone.

Moisten the rooting medium, place the stem in the medium and place everything in plastic wrap to conserve moisture. However, do not put it in direct sunlight. After rooting, you will have a small plant with a good root system, ready to transplant.

The important thing to remember is not to let it dry out. Keep it moist, but not too wet, since you do not want fungal diseases to develop. This is true for the other types of cuttings that I mentioned.

Layering is another way of propagating plants. Some plants, such as brambles, do this naturally. Here, you encourage rooting on a stem while the stem is still attached to the mother plant. Types of layering include simple, air, tip and compound.

Simple layering, sometimes called trench layering, is easy. Bend a branch to the ground and cover it with several with several inches of soil. Be sure that the tip of the branch extends above ground level. Make sure everything remains moist, and eventually new roots will form along the branch. Sometimes wounding may speed up the process.

The last method I will mention this week is division. Here, you are cutting or pulling apart the appropriate plant structure to produce new plants. This works best for some herbaceous perennial plants. The parts of the plants used may include crowns, bulbs, corms, rhizomes, tubers, stolons or suckers.

If you have ever grown irises or day lilies, and needed to move them, you are probably familiar with this process. If they don’t break apart easily after you dig them up, you can cut them into more manageable sizes with a knife.

In my next column, I will cover plant propagation methods which require a bit more skill. These include grafting, budding and tissue culture.

Part 3

For my last column in this series on plant propagation, I thought I would cover some of the more challenging methods of this art: grafting, budding and tissue culture.

Grafting involves joining separate plant parts together to form one plant. There are two parts to the graft. The first part is the scion, which is the part at the top of the graft. This is the cultivar that you are interested in propagating and will bear flowers and fruit.

The second part of the graft is the rootstock. Rootstocks are often chosen for their disease resistance and/or size control. Fruit tree rootstocks show a wide range of size control options, from dwarfs to semidwarfs to almost full-size trees. A good example of rootstocks used for disease control occurs in vegetables, where plants with resistance to soil-borne diseases can be selected to serve as rootstocks for a cultivar that is susceptible to a particular disease that may be infesting your soil.

Yes, there is science behind grafting, but it is also an art that calls for a lot of practice to find success. There are many different types of grafts, and if you would like to try your hand at making a graft, get a good book on the topic.

Budding is similar to grafting, except you are removing a single bud from the cultivar you wish to propagate and placing it on another plant, which will eventually serve as the new plant’s rootstock.

There are basically three methods of budding: T-Budding, Chip Budding and Patch or Shield Budding. Like regular grafting, some skill in the art of carving wood is needed.

The trick for grafting and budding is the ability to match up cambium layers so that they will grow together properly. The cambium is the part of the plant that is forming new cells — xylem to the interior of the plant and phloem to the outside. If this is not done properly, the graft will fail. I should also mention that keeping everything clean is critical. You do not want to introduce a pathogen into your graft.

Tissue culture is the final method of plant propagation that I will mention. This falls in the category of “Don’t try this at home,” at least in my opinion. This requires surgically-clean conditions and special lab techniques. Commercial labs can do a great job with tissue culture, providing disease-free plants if the right techniques are followed.

I will close with another precaution. Be sure that it is legal to propagate the plant that you are interested in. There are two laws regulating this area.

The Plant Patent Law protects vegetatively-propagated plants. This law was enacted to protect plant breeding programs and encourage the development of new cultivars. Patent holders have the legal right to control reproduction, and thus you are not allowed to propagate these cultivars, even for home use. The Plant Variety Protection Act is similar, protecting seed-propagated cultivars.

Writer: Timothy Baker

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