Nuts. Not the type you sometimes have to work with, but the ones that come in a can and you enjoy as a snack. Peanuts, walnuts, almonds, macadamia nuts, hickory nuts, chestnuts, even cashews. We consider all of these nuts even though they may not fit the biological definition.
True nuts, biologically speaking, have hard shells that don't split open when mature. The stony or woody shell is the ovary and the kernel is attached or fused to the ovary wall. The walnut fits this definition. While the English/Persian walnut is quite easy to break open, you have to use a hammer on a black walnut to get to the kernel inside and then you have to tease the meat out of the recesses of the hard shell to which it is stuck. Some people drive their car over black walnuts to crack them open.
A wide variety of dried seeds are called nuts in a culinary sense yet only ones that include fruit that do not split open are considered true nuts in a biology context. The almond, a relative of the peach, is not a true nut. The pistachio is not a true nut as it splits open when mature and the seed is not attached to the shell.
The peanut is not a true nut but a member of the pea family. If you have ever grown peanuts you know the flowers are borne above ground, like peas. After being pollinated, the flower stalk elongates and pushes the blossom under the ground where it develops into a "pea pod" containing one to four seeds. Peanuts are typically grown where the soil is sandy making it easier for the flower stalk to push into the ground. Some local gardeners have told me they cover the elongating flower stalk with compost or mound compost around their plants to make it easier for the flowers to bury underneath. Most of the countries I've worked in call the peanut a ground nut even though it is a legume just like peas and beans.
The cashew is the strangest nut I've ever run across. Even though it is not a true nut based on the biological definition, I particularly like cashews and dig them out of the cans of mixed nuts before I eat any of the other nuts. My Pekingese also likes cashews, preferring them to every other nut I've given her.
The first time I saw the type of fruit the cashew comes from I was working in Mozambique. The young boys would line up along the road with bowls of freshly roasted cashews waiting for any vehicle to drive by. The fruit looked like a shriveled pear with a kidney-shaped structure hanging below. The pear shaped structure originates from the flower stalk and flower receptacle, the structure where the ovary is attached. After pollination these swell and form what is called a cashew apple from which a flavorful drink is made. The cashew apple in my photograph looked more like a swollen stem to me but had not yet swollen into the cashew apples. In Mozambique the apple is used to make a powerful alcoholic beverage which I'm sorry I did not have an opportunity to try. My interpreter was Sunni and he didn't drink but others I worked with did. Mozambique had a number of great local beers but I never had the opportunity to taste their cashew apple beverage.
The kidney-shaped fruit contains a single seed, the cashew nut, bathed in a skin irritant related to the toxin of poison ivy. To harvest cashews, gloves need to be worn and the seed is roasted to detoxify the poison.
Hopefully, if I have an opportunity to return to Mozambique or another country where cashews are grown I'll be able to take advantage of the harvesting process and maybe even taste the beverage made from the cashew apple. Every time I snack on cashews I think of those entrepreneurs in Mozambique lined up along the road with their cashews.
Dr. Curtis E. Swift is a retired horticulture agent with the CSU Extension. Reach him at Curtis.Swift@alumni.colostate.edu or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.