The Violet Gazette
Return to AVS Homepage
Return to The Violet Gazette Index
Return to The Autumn 2000 Contents

© 2000 All Rights Reserved.

Volume 1, Number 4
Autumn 2000
On line Version


Why violets are so successful
Written by:  Theresa M. Culley, Ph.D.

Theresa M. Culley, Ph.D., the newest member of the board of The American Violet Society, holds a postdoctoral position at the Department of Ecology & Evolutionary Biology, University of California, Irvine. Her research interests include plant population ecology, pollination biology, conservation of rare species (especially Hawaiian endemics), population genetics, statistics, and community ecology.

Theresa's Current Violet Research


Image of Downy Yellow Violet Chasmogamous (CH) Flower
(Figure 1.)  Chasmogamous (CH) Flower Of The
Downy Yellow Violet, Viola pubescens

            As anyone knows who has violets growing in their garden or front lawn, they have an amazing ability to persist and even to spread across an area over time. A small violet in a garden may live for a year or two before many others appear in neighboring flowerbeds. Over time, violets may thread themselves through the lawn, like scouts before an impending army. Other species prefer to sit patiently in the soil, awaiting the occasional arrival of a fellow member. How do these violets survive so long and why are they so successful?

             Many violet species thrive because they are able to do a number of different things. First, many species can produce seeds through two different types of flowers. Showy chasmogamous (CH) flowers (Fig. 1), so familiar to violet fanciers, are often visited by insects, which promotes cross-pollination between different plants. In contrast, closed cleistogamous (CL) flowers resemble small buds that never open (Fig. 2) and are produced near the top or at the base of the plant. The self-pollinated CL flowers are often viewed as the "back-up plan" in case pollinators are scarce any one year, ensuring that the plant can still make seeds. These two flower types also allow some violet species in deciduous forests to produce seeds in two totally different environments. For example, in the downy yellow violet, Viola pubescens, CH flowers appear in the early spring in the bare forests as other spring ephemerals begin to flower. During this time, light can easily reach the forest floor, and insects are likely to find and visit the showy flowers. However, plants stop making the CH flowers once leaves start forming on the trees above. As the amount of light on the forest floor drops to about 7% of what it once was and other spring ephemerals die back (e.g., Trillium, spring beauty), V. pubescens begins to make the self-pollinated CL flowers. An individual plant usually produces similar numbers of CH and CL flowers (about 3-5). Both types of flowers also have similar numbers of seeds per fruit (8-11). Thus, many violets can still continue to produce seeds under conditions that are unfavorable to other plants.

Image of Downy Yellow Violet Cleistoogamous (CL) Flower
(Figure 2.)  Cleistogamous (CL) Flower Of The
Downy Yellow Violet, Viola pubescens

             Violets are also successful because of the way they disperse their seeds. Both CH and CL seeds in many species are ballistically scattered over long distances. This happens as the three valves (sides) of each fruit dry and slowly squeeze shut, effectively shooting out the seeds over a period of an hour or more (similar to pinching marbles between two fingers). For example, the downy yellow violet, Viola pubescens, and the Canadian violet, V. canadensis, scatter their seeds up to five meters away. In some stemless species (e.g., Viola sororia), the CL fruits can even turn down into the soil and slowly spiral along underground for a foot or so, before emerging to release their seeds. Many violet species also have a second way of dispersing their seeds. These violets produce a pale-colored, protein-rich structure (called an elaisome) attached to their seeds. This structure is a favorite food of ants, which will find the seeds on the ground and carry them back to their nest. There they gnaw off the elaisome and dump the seeds into their nutrient-rich underground trash heap, which is a great place for seeds to grow (if not too deep underground). Such ant-dispersal often results in seeds traveling another meter or so away from the mother plant (Culver and Beattie, 1978). Because of these two ways of dispersing their seeds, some violets can easily spread over an area within a few years.

             Another reason why violets do so well is that most species are perennial and several also reproduce vegetatively, thus persisting for long periods of time. These types of violets often send stolons or runners aboveground (e.g., V. lanceolata, V. blanda) to form new plantlets. Often in a patch of violets, what looks like many plants clustered together is only one individual. That is, the plantlets can usually be traced back to a common origin. In this case, each plantlet is known as a ramet and the entire group of ramets is called a genet (i.e., a genetic individual) or a clone. Together with its perennial habit, this type of clonal growth ensures that the individual plant can survive and grow larger from year to year.

             Violets also have an advantage over other plant species because they have an underground storage structure, the rhizome. This is actually a horizontal stem, often with scalelike leaves and buds, that allows plants to survive harsh conditions by storing up nutrients. Rhizomes are very important in cold climates, dry areas, and in lawns that are frequently mowed. The rhizome is also a means of vegetative propagation because it may sometime branch, forming a new ramet that usually remains attached to the mother plant (e.g., V. sororia; Solbrig, 1981).

Image of Downy Yellow Violets In Spring Bloom
(Figure 3.)  Downy Yellow Violet, Viola pubescens
In Full Spring Bloom

             So it appears that the main reason why violets are so successful is that they have become well-adapted to persisting in and invading new areas. Several violet species are better at this than others because they possess several of the above characteristics. These plants are likely to produce both flower types, have seeds that disperse far, reproduce vegetatively (in addition to the sexual reproduction), and have a large rhizome. On the other hand, other violet species that have only a few of these qualities may be more likely to be solitary and spread very slowly. However violets persist and spread, they continue to delight the viewer with their vibrant array of color each spring. For the true violet fancier, the sight of a group of violets flowering is a sight to behold for many days to come (Fig. 3).

© 2000 Theresa M. Culley, Ph.D.
For The American Violet Society
All Rights Reserved


Literature Cited 
Culver, D.C., and A.J. Beattie. 1978. Myrmecochory in Viola: dynamics of seed-ant interactions in some West Virginia species. Journal of Ecology 66: 53-72.
Solbrig, O.T. 1981. Studies on the population biology of the genus Viola. II. The effect of plant size on fitness in Viola sororia. Evolution 35: 1080-1093. 

Return to The Autumn 2000 Contents
Return to The Violet Gazette Index
Return to AVS Homepage