Plant Propagation

What Are The Pros and Cons of Propagating Plants with Cutting vs Seeds?

The two most common ways to propagate plants are by seed or vegetative cuttings (stem, root, leaf, or tissue culture). While seeds preserve genetic diversity and give rise to new varieties, vegetative propagation can clone and preserve existing varieties. Here are some pros and cons of seeds and cutting.

Seed Propagation

Seeds have parents and are the result of cross-pollination between two different plants or single self-fertile parent. Each seed is the result of sexual-reproduction and is genetically distinct from its parents and each other. Seeds that resemble their parents are said to “come true to seed”. While some plants come true to seed others, like apples, rarely resemble their parents.

Pros of Seeds

• Seeds are genetically distinct from each other and their parent plants.
• Desirable traits can be selected for via careful plant breeding.
• Seeds create and protect genetic diversity. Genetic diversity creates resiliency from climate, pests, and disease stresses.
• The random recombination of genes can new yield new traits; desirable fruit, cold hardiness, etc.
• Seeds yield new cultivated varieties (cultivars).

Cons of Seeds

• Seeds are genetically distinct and are thus inherently less predictable than cuttings.
• Not all plants come true to seed.
• Difficult to control cross-breeding in an open-pollinated environment.

Vegetative Propagation

Vegetative propagation is the process of starting a new plant from a root, stem, leaf of an existing plant and results in a genetic clone. Cuttings are most useful when trying to preserve specific traits such as growth habit or fruit quality. Since seeds are genetically distinct, the only way to maintain a cultivated variety is to keep it under continuous vegetative propagation. The original Granny Smith apple was a seedling discovered in 1868 and cloned to produced every Granny Smith apple tree in existence. The Annurca apple, a seedling of Italian origin, has been growing since the year 0079 due to continuous vegetative production.

Pros of Vegetative Propagation

• Vegetative propagation produces genetic copies of their parent plants enabling the preservation of cultivated varieties of plants that don’t come true to seed. Without vegetative propagation, cultivated varieties would be lost at the end of the original plant’s life.
• A single parent plant can yield a large number of cuttings for propagation.

Cons of Vegetative Propagation

• Vegetative propagation reduces genetic diversity and can leave plants susceptible to shocks such as climate changes or the introduction of pests and diseases. The practice of propagating potatoes via tubers (instead of seeds) made Irland’s potato crops susceptible to potato blight.
• Some plants are difficult to propagate vegetatively.

Is this plant self-fertile or does it need a pollinator?

Do Baby Plants Have Parents?

Each Spring and Fall I give tours to of the Northlands Urban Farm to elementary kids, and at one point we usually find ourselves sitting in the strawberry patch and talking about flower, fruit and seeds.

“Can anyone tell me what all of thiese tiny little dots along the side of the strawberry are?”

“Those are seeds!”

“That’s right! And what are seeds? What do they do?”

“They grow into plants!”

“They do! Seeds are baby plants. Let me ask you a strange questions. Do baby plants have parents?”

*uncertain and confused looks*

As it turns out, baby plants do have parents. A seed is the result of sexual reproduction in which pollen (male) from one flower comes into contact with the ovary (female) of another. Some plants have separate (imperfect) male and female flowers while others have (perfect) flowers that contain male and female parts. To further complicate things, plants can be male, female, or both.

• Dioecious species have separate male and female plants. Ex; Hops, seabuckthorn, willow, poplar, honeylocusts, and arctic kiwi.
• Monoecious species have separate male and female flower on the same plant. Ex; corn, birch, pine, hazelnut, and squash.
• Unisexual species contain perfect flowers

Self-Pollination

By definition, self-fertile plants are both male and female and are self-pollinating when pollen from its male organs is capable of fertilising eggs in its female organs.

While self-pollinated seeds have a single parent, they will not be an exact copy (clone) of their parent plant. Clones are made by taking vegetative cuttings.

Cross-Pollination

There are two main reasons why a plant is unable to fertilise itself. The first is that the plant is male or female. While both male and female plants will produce flowers, only the female plant will produce seeds (or fruit). When this happens, it is necessary to plant male and female plants to create seeds or fruit.

To increase genetic diversity and decrease inbreeding, the (male) pollen of some plants is incapable of fertilising its own (female) eggs. While this strategy may reduce the number of seeds that a plant produces it will increase the genetic diversity of those seeds by ensuring that they are the result of cross-pollination with another plant. An increase in variety increases the odds that some of the seeds will germinate and survive until reproductive maturity.

Plants that need a pollinator include:

• Any plant whose pollen and eggs are incompatible with each other.
• All species that contain separate male or female plants (dioecious species).

The seeds that result from cross-pollination are a genetic cross between two parents. While this process is usually left up to chance (wind or bees), it is sometimes the conscious result of human intervention. Plant breeders take advantage of cross-pollination by collecting pollen from one plant to fertilising another in an attempt to breed new plants with desired traits.