Botany: The Seven Most Common Families of Plants, Lesson 3: The Pea Family

Sweet Pea Color Plate
"The sweet pea has some of its leaflets changed to tendrils which hold it to the trellis. Its flower is like that of the clover, the upper petal forming the banner, the two side petals the wings, and the two united lower petals the keel which protects the stamens and pistil."
-Anna Comstock, Handbook of Nature Study, page 589



We learned about the family in our botany studies, which is characterized by its irregularly shaped flower containing five petals: a banner, two wings and a keel (which is comprised of two petals that look like one).


The Pea Family also produces pea-like pods that open along two seams and often have pinnate (opposite) leaves. We don't have any peas growing in the garden and we have never been able to find any blooming members of the family in our neighborhood except the clover. I have invited the boys, in the past, to find clover in the backyard and to bring some inside to sketch, and when they did, they found White Clover.
July 2009



The clover's petals are hard to identify as a banner-wings-keel because they are so long and thin, but looking at the clover closely, they noticed that the flower is made up of many small flowers, each with their own calyx. Several years ago, Katie examined some clover thoroughly and was able to draw the flower as it looks from far away and then a cut-out that shows the flower pattern.


July 2009


 "The white clover has creeping stems. Its flowers depend upon the bees for their pollination and the bees depend upon the white clover blossoms for honey." Handbook of Nature Study, p.597

Sam noticed several years ago, when we studied white clover, that the bees were swarming the clover one day but not so much the next. We had learned the previous year, when we studied bees, that bees choose a different flower each day to get the nectar from, so this made sense.
July 2009

They also noticed that the flowers are not all just white. The leaves, too, are not just a single green, but several shades and some even had hues of red in them. Other members of the Pea Family include lupine, most beans and legumes and alfalfa.



Flowering plants have been divided into two major groups, or classes,: the Dicots and the Monocots. Since one of the main divisions between Monocots and Dicots has to do with their seeds, you can look at the differences by soaking a corn seed and pea seed or bean seed in water overnight and then comparing the two. The pea or bean, being a dicot, breaks into two parts and the corn seed, being a monocot does not. If you decided to sprout the two different types of seeds you can further see the differences when the cotyledons develop. Cotyledons are the "seed leaves" produced by the embryo .The number of cotyledons found in the embryo is the actual basis for distinguishing the two classes of angiosperms, and is the source of the names Monocotyledonae ("one cotyledon") and Dicotyledonae ("two cotyledons"). The cotyledons serve to absorb nutrients packaged in the seed, until the seedling is able to produce its first true leaves and begin photosynthesis.



Other ways of determining a dicot from a monocot include:




  • Number of flower parts: If you count the number of petals, stamens, or other floral parts, you will find that monocot flowers tend to have a number of parts that is divisible by three, usually three or six. Dicot flowers on the other hand, tend to have parts in multiples of four or five. This character is not always reliable, however, and is not easy to use in some flowers with reduced or numerous parts.
  • Leaf veins: In monocots, there are usually a number of major leaf veins which run parallel the length of the leaf; in dicots, there are usually numerous auxillary veins which reticulate between the major ones. 
  • Stem vascular arrangement: Vascular tissue occurs in long strands called vascular bundles. These bundles are arranged within the stem of dicots to form a cylinder, appearing as a ring of spots when you cut across the stem. In monocots, these bundles appear scattered through the stem, with more of the bundles located toward the stem periphery than in the center. 

  • Those are the basic ways to determine the difference between Monocots and Dicots. There are other ways to tell them apart, such as pollen structure and root development.

    Why is it helpful to know the differences between them? Again, it is easier to look a plant up if you can determine which category it falls in. Plant Field Guides are written by botanists, so it is helpful to be able to think like a botanist, if you want to find things in Field Guides.

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