Food storage and geophytes

Potatoes are tubers. Tubers are are type of geophyte. Geophytes are plant organs used to store food and water. They are also used in asexual reproduction. There are several types of geophytes: bulbs, corms, and everything else. That “everything else” is what we call tubers. Potatoes and yams are stem tubers. Stem tubers can emerge from modified stems. These stems can start out as stolons or rhizomes. Stolons are stems that grow at or just below the soil surface as “runners”. These “stems” are converted into adventitious roots at the nodes and what would have been a bud above ground becomes a spud below. Rhizomes are 'runners' that connect a parent plant to its offspring.

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A modified stem

The “eyes” seen on a potato are actually stem nodes. Within each potato, you will find the same plant cells you would find above ground: vascular bundles, pith (spongey tissue), and cortex (outer tissue). Now here’s the funny part. While our standard spud grows from stem tubers, sweet potatoes grow from root tubers. The internal cell structure is very different. Root tubers have no nodes. That is why sweet potatoes have a more elongated form. At one end, you will find crown meristem tissue, which grows into stems and leaves. At the other end, called the distal end, the tuber produces roots. But enough of that, let's start growing some potatoes!


Commercial potato farming

Growing potatoes is surprisingly easy and I urge you to give it a try. In his book, The Botany of Desire, Michael Pollan describes how many potato farmers will not feed what they’ve grown commercially to their families. This is because of all the fungicides, herbicides and pesticides that are applied to commercial crops. Mr. Pollan learned that they grow a separate crop for their family, using a significantly lower amount of chemicals. Huh.


How to grow potatoes

While potatoes can can certainly be grown from spuds bought at the grocery store, this is a bad idea. Foods bought in the store are safe for human consumption, but they are not guaranteed to be free from common garden pests and diseases. You don’t want to introduce Phyophthora infestans, the cause of potato blight, into the garden. You are far better off buying certified “seed potatoes”.


The easiest way to grow potatoes is in a barrel, raised bed, or in a tower. If potatoes are planted in the ground, you will be finding rouge spuds for many years. Also, digging them up from the ground is, let’s face it, work. Growing potatoes in containers makes harvesting significantly easier and they make nice summer patio plants!


To begin, fill the bottom of the container(s) with 4" of loose, moistened soil. Cut seed potatoes into 2 inch chunks, making sure that each chuck has several eyes (small seed potatoes can be planted whole). Place the chunks 6" apart and cover them with 3" of moistened soil and repeat the process until the container is filled. Water lightly and be sure to place planters where they will get lots of sun. To build a tower (which works nicely for strawberries, too), simply take a section of chicken wire or hardware cloth and create a cylinder. Landscape cloth can also be used, but it may fall over. You can also grow potatoes indoors, near a window, if it gets enough light! Potatoes need loose, well-drained soil and frequent, light watering. Never let potato plants sit in water, they will rot. Potatoes use a lot of nitrogen and potassium, and they prefer acidic soil (as low as 4.8 pH).


At first, it will look as though nothing is happening. As a gardener, you know the value of patience. With time, water and sunlight, tubers will send out roots and stems that will pull nutrients from the soil and create carbohydrates out of sunshine. (Don’t you just love photosynthesis?) Before long, the container will be filled with lush, green growth. Aside from occasion watering and feeding (aged compost works great!), that’s all you have to do until it completes the season’s life cycle.


Harvesting potatoes

Eventually, the lush above ground growth will start to die off. When it starts looking ragged, dump the contents of the container out on a tarp and remove the mature potatoes. Now comes the really cool part: mix the remaining soil with some aged compost and do it all again with the immature spuds! I have been growing potatoes from the same batch of seed potatoes for six years! And, honestly, homegrown potatoes taste far better than store bought spuds.


Pests and diseases of potato

Now, we’ve all heard about the Great Potato Famine of 1845-1852. Over 1 million people starved to death and another million abandoned Ireland, all because of potato blight. Potato blight is a fungal disease that causes the tuber to rot in the ground. This is why so many chemicals are commonly used when growing potatoes, but small-scale potato gardening can do without.


Give potatoes a try today!

Tubers are ‘taters, but there’s more to them than that.


Tubers are modified underground stems (geophytes) that store water, sugar, and other nutrients, to get plants through winter and drought, to help them start back up in spring, and to regenerate themselves, asexually. Some people say that underground runners (stolons) are also tubers, but not everyone agrees.

Stem tubers

Potatoes and yams are stem tubers. These structures are modified stems from thickened stolons (runners) or rhizomes (underground stems). The ‘eyes’ you see on a potato are buds. New plants can grow from these buds, as well as from the distal (far) end of the tuber.


Root tubers

Root tubers, or tuberous roots, on the other hand, are modified lateral roots which store nutrients and sugars in the same way as stem tubers. Sweet potatoes, dahlias, and cassava (tapioca) are examples of root tubers. These tubers do not have ‘eyes’ that can generate new plants. Instead, growth occurs at the far (distal) end, as well as from the crown area where foliage is already growing. Tuberous roots are biennial:

1. The first year, root tubers are generated.
2. At the end of the growing season, the above ground portion of the plant dies.
3. In spring, the root tubers generate new plants before shriveling up and disappearing.

What sort of tubers are you growing?