Plant Morphology 101: Understanding Structure from Roots to Flowers

The shape of things

 "Morphology" - from the Ancient Greek - (morphḗ) meaning "form", and (lógos) meaning "study". In Botany it is used to classify plants based on the shape of their parts. 

Why pay attention ?

 What a plant looks like can give hints as to where it evolved and therefore where to place it in a garden! Focusing on the plants' main characteristics will help you to make a better decision on compatibility with other plants, as well as cultural care.In teaching proper plant selection to our staff , it is more valuable to show them the morphological trait effects of environments on plants, than to have them memorize the characteristics of every plant we use.  This way they can always determine how well a plant would thrive into where they want to use based on the characteristics they see. Even if it is a new variety or species they have never seen before! 

Adaptation and ecosystems

 Hairs, glands, the wax on leaves and stems, the shape of the leaf tip, leaf color, are all key indicators of environment.  Bark, cork formation, the presence of resin (pine oil) or latex (white rubber), as well as mucilage (gum) also tell us something about where the plant lives naturally.  The presence of thorns, the type of root, leaf thickness, and leaf shapes are also examples of morphological adaptations to separate and distinct ecosystems.Lets look at an example.  In horsetails, the plant evolved hollow stiff stems that are very light – the reason is the stem walls have silica (sand) in them.  In fact, the stems were used as scouring pads in colonial times! The function of the silica is not just for rigidity, but as well the ability to grind down herbivore chewing parts. Eventually - deer and friends learn to avoid eating horsetails !This tells us that horsetails are a good candidate for placing in a garden which might get deer. Obviously not in a NYC rooftop ! But hey ! You never know. 

Horsetails !

Adaptation and use 

 Depending on where on the planet you evolved, hairs could be an adaptation to windy environments as well as to growing on a rain forest floor. In windy locations, they basically slow down the speed of air over the leaf surfaces and thus reduce transpiration loss. The hairier the leaf, the windier the location where it evolved – see Dusty Miller below.  But Saintpaulia and Streptocarpus which are tropical rain forest floor plants use the hairs to "bead" the constant rain off their leaves. 

Dusty Miller thrives in sun and wind. 

        African violet

The drops are held up over the leaf surface and it rolls off !

 Wax on leaves is another good example.  Its not just about water loss – hence a hot, dry environment, but shady or rainy cool forest too.  Usually, the more wax you see on a leaf or stem, the drier the environment - like in many cactus .  But in species like Hosta which evolved in shady cool damp forest floors, or Phalaenopsis orchids which evolved in tropical areas near waterfalls, wax is used to protect the leaf from excess moisture which invites molds ! 

Wax keeps water off leaves! 

                            Waxy flowers are common in rain forests

Combinations 

 Sometimes..... its the combination of several characteristics that gives a clue to the environment.  We know that the whiter the wax, the sunnier the location - as white reflects more sun. But hairy leaves with white wax are from dry, sunny and windy places. Like Lavender ! 

Vive Provence !

 Leaf tips that droop or come to a long sharp point are from plants that evolved in rainy environments. The function of the tip is to quickly move the water off the leaf surface. 

Take a look at a birch leaf tip !

Leaf color 

 Leaves are seen green because of the copious amounts of chlorophyll in them. The darker the green, the more chlorophyll in the leaf.Olive colored leaves are an indication of full sun plants.  These don't need that much chlorophyll under the baking sun.  Dark green leaves an indication to preference for partial sun.Plants that prefer shade become pale olive green in more sun, whereas small olive colored leaves turn darker when placed in lower light. 

Leaf width

 There is also a direct relationship to light and leaf width. Plants that evolved in Full sun tend to have smaller leaves, while shade leaves tend to be wider.Some species are able to adapt somewhat to both. Mainly those with a flat leaf blade. Their leaves become wider and thinner in a lower light situation, or the reverse in full sun.  Needle evergreens do not adapt - and are intolerant to low light. 

Leaf shape

 Plants that have with cylindrical, spherical or scale like leaves such as needled evergreens (Pines, Cypress) are full sun plants only.  They are unable to go through morphological changes to adapt and usually perish in any lower light environment they get placed in.The cylindrical shape itself is an adaptation to full sun and windy conditions as this shape reduces evaporation.

Cylindrical pine leaf. 

Variegation

 Variegated plants have leaves with sections in them that contain little to no chlorophyll. Sometimes the transparency is colored by red anthocyanins or carotenoids, causing the variegation to be pink or yellow.Leaves containing any variegation will require more sunlight, or more sunlight hours per day to compensate for the lower capacity to produce sugars. Most extreme examples are actually man made and occur infrequently in nature. 

Full sun variegated dogwood

Pink variegation in beech.

Red and purple

Plants with red or purple leaves as in purple beech or maple have many anthocyanins in them that mask the green chlorophyll.  They tend to be plants that evolved in full sun, where the anthocyanins are acting as a sun block. 

Purple basil needs sun !

The color also has partially to do with their need to use the blue wavelength in light to photosynthesize. Because blue light is quickly filtered through leaves, it rarely reaches plants in partial sun or shade. Some species with red or purple leaves are simply unable to adapt to these lower light levels. 

Red leaf Japanese maple

 Sometimes however, a purple or red leaf plant placed under a canopy or shade turn greener or loses the red or purple altogether.  That is because you don't need sunblock in the shade! 

Purple leaf Japanese maple reverting to green in the shade.

For the right plant in the right spot ask one of our Design Team members. 

They know their morphology !

Call Plant Specialists TODAY !

Don't delay – the sooner the better !

GREENING NEW YORK FOR OVER 51 YEARS !

   Article written by our Staff Horticulturist, Peter B Morris, BSc, MSc, MBAAll photographs used with permission @SHUTTERSTOCK