April Plant Fact



petals petals petals


April brings forth a bevy of floral color, which is a much welcomed sight after many months of gray winter doldrums without any color of much significance.  Although we as gardeners delight in the color of flowers, it is typically a part of the plant to which we give little thought other than they most likely developed in order to attract pollinators.  Flowering plants are the most modern of plants and are categorized under the general heading of Angiosperm.  Angiosperm translates into "Seed in a Vessel’" describing how the ovules or "egg" are held within a protected ovary.  Fossils of the very first Angiosperms date back about 125 million years, although they undoubtedly appeared earlier.  Just as with the pine cones of Gymnosperms, the reproductive or floral parts of angiosperms developed from leaves and stems, although there is currently not a defined fossil trail that describes how flowering plants slowly developed to this stage.  Interestingly, there are several different paths in which "petals" actually developed.  The long held belief is that petals developed from anthers, which is true for many Angiosperms.  In fact, most times that a "double flower" or a flower which has more than one whorl of petals appears, the additional petals invariably were anthers that mutated into a sterile petaloide form.  However, for many other flowering plants, true petals actually developed from leaves and not from anthers.  To confuse things further, some flower "petals" that we see in the garden today are really modified leaves or bracts!  Subtending a flower is a modified leaf called a bract.  In many plants, the bract becomes enlarged and colorful, appearing identical to a true petal!   The "petals" of Flowering Dogwood (Cornus florida) pictured above (or Cornus kousa), or the red "petals" of Poinsettia (Euphorbia pulcherrima) or any other Euphorbia is actually a modified bract!  To make things even more complicated, the outer covering of a flower bud is called the calyx and is composed of individual modified leaves called sepals.  In some plants, the petal and the sepal are both ornamental, but have a different physiological appearance, such as Snowdrops (Galanthus species).  For many other plants, the sepals and the petals appear identical and are termed Tepals.  Plants that fall into this category include Magnolias (pictured at the above) and Tulips!   
Many flower petals include markings that guide the pollinator to the floral center and to the ring of anthers.  Some of these markings are visible to the naked eye. However, most insects can "see" or interpret wavelengths in the UV spectrum, which humans cannot see.  In other words, insects can see patterns that we cannot!  Of course, there needs to be a reason why pollinators wish to visit a flower in the first place!  Most plants have developed Nectaries, which are regions that contain a sugary or a high carbohydrate "food" that acts as an incentive for the insect to visit the flower.  For those flowers in the Buttercup Family, including the Hellebores (Helleborus) pictured above and Winter Aconites (Eranthis), the petal had become modified to become a horn-like nectary that appears next to the anthers and the ‘petals’ are actually modified bracts!  To make things even more intriguing, some plants do not use nectaries to attract a pollinator, but the petals have become modified such that they appear like a "mate" for the pollinator.  This alteration is referred to as mimicry and is the manner in which most orchids attract a pollinator.  In other words, if one has ever wondered why orchids have developed such an intricate floral structure, it is simply a method for attracting a pollinator!