Thursday, August 12, 2010

Some Things About Potatoes

Harvesting volunteer potatoes.

Volunteer plants are those that grow in the garden even in the absence of intentional care.  Volunteers arise from plants whose seeds and vegetative parts (such as rhizomes, tubers, roots and stems) survive under neglect.  This is natures' way of maintaining vegetation on this planet.  But when gardeners were born and their designs were printed, some of these volunteers have been labeled as weeds. 

In my garden potatoes would grow voluntarily every year even if I only planted once.   These are the potatoes that skipped my trowel during the previous harvest.   Early in the spring they would sprout right where they were left.   After three to four months when the leaves begin to turn yellow, we are ready to unearth the goodness that lies underneath the soil.   Today I will use these volunteer potatoes to share some useful lessons in gardening that I learned over the years.  Did I mention that I once was a potato scientist working with the International Potato Center in my younger days?  

Potato (Solanum tuberosum):  Tubers were very close to the soil surface.

A tuber hangs among many roots.

Tuber.  The part of the potato that we eat is called a tuber. It is a modified stem...not a root.    That's right the potato is technically a stem.   Tubers grow from a stolon which is a stem that grows underground.   This can be easily distinguished from the roots by their size and color.  Stolons are white and are much thicker than the roots. 

Tuber - "Bigger than my hand!"

Eyes.  The indentations on the potato tubers are called eyes.  Although they cannot see, believe me these eyes have brows. :)  Observe them the next time you peel some potatoes.   The eyes are the nodes of the modified stem.  On a regular stem, this is where branches would come out.  That is why when you keep your potatoes in your pantry for a long time, sprouts would come out.  If you plant those sprouting potatoes, those sprouts become the plants.  Did you know that potato varieties with deeper eyes are less desirable than their shallow-eyed counterparts?

Tubers harvested from one potato plant.

Greening.  Notice that the potatoes although harvested from the same plant did not have the same colors.  Some of them are green.  Greening in potatoes is the development of chlorophyll on the tubers caused by the exposure of the tubers to light.  The absence of hilling-up (raising the soil around the base of the plant) on these potatoes resulted in tubers that grow very close to the soil surface and thus exposure to sunlight. 

To prevent greening - always store your food potatoes in a dark place or cover them with a towel.  I don't recommend eating potatoes that show signs of greening for these reasons:  they don't taste good; they don't cook easily; and most of all they contain some amounts of toxic substances (glycoalkaloids).  

Ugly potatoes with enlarged lenticels

Lenticels.  These are small openings on plant tissues that allow gas exchange.  In other words, they likened to the nostrils.  The bumps seen in the picture above are not diseases; they lenticels that have been enlarged.  The volunteer potato that we harvested was growing next to a leak in the drip line which created an anaerobic (absence of air) condition within the soil.  The lenticels had to open, as flared nostrils, in search of oxygen.  This is what happens when plants are over-watered - the lenticels swell and they can be a convenient entrance for microorganisms. 

I have to stop here but expect for more posts on potato-related topics in the future. 

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