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What Is Pith?

A cross-section diagram of a leaf, showing its pith, also called xylem.
Grapefruit and other citrus fruits contain spongy white pith (albedo) that sits between the skin and the flesh.
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  • Last Modified Date: 19 November 2014
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In botany, pith is a term used to refer to a spongy, usually soft, substance that is found in the middle of the stems and roots of many plants. Another name for this tissue is the medulla. The medulla tissue is made up of a particular type of plant cell, called parenchyma cells, which tend to be relatively large, with thin cell walls. The main functions of this tissue are nutrient storage, and the transport of nutrients through the stem, branches, leaves, and roots of the plant. A secondary definition of the term pith is in reference to the pale, spongy inner layer of rind, more properly called albedo, which is found in citrus fruits.

New pith growth is usually soft, spongy, and white or pale in color. As the tissue ages, it commonly darkens to a deeper brown. Tree pith is generally present in young growth; in the trunk and older branches, it is often mostly replaced by a woody substance called xylem. In some plants, the medulla tissue in the middle of the stem may dry out and disintegrate, resulting in a hollow stem.

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Most, or all, vascular plants, also known as higher plants, have at least some medulla tissue. A key characteristic of these plants is their ability to conduct water and nutrients throughout the structure of the plant, a function in which pith plays an important part. This ability to move substances up and down the stem, and along the branches, has allowed vascular plants to evolve into species that include specimens of a very large size. Non-vascular plants, conversely, which includes plant families such as mosses, liverworts, and algae, possess neither medulla tissue, nor a transport mechanism, and this means that they can only grow to a very limited size.

Humans have found numerous practical uses for medulla tissue. In Asia, the medulla of a shrub called the rice paper plant is used to make edible rice paper. Wicks for candles have been made from the medulla tissue of certain species of rushes. The pith of a plant called the sola, which grows in swamps in India, has even been used to manufacture lightweight helmets designed to protect the wearer from the heat of the sun. These pith helmets were once popularly worn by Westerners in tropical climates, and are still frequently used in Vietnam.

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kylee07drg
Post 5

Pith hats can keep you really cool. Because pith can retain water so well, you can soak the hat in cool water before putting it on. It won't even lose its shape when wet.

Oceana
Post 4

I heard about coir pith when I started researching ways to improve my garden. This is coconut pith, and it can really improve your soil.

It has lots of nutrients, and it's the best soil conditioner I've ever used. It makes the soil retain water, which is good for me, because I live on a hill and water tends to run right off.

I've heard that this is the same stuff they use to make doormats and rugs. It's pretty multi-functional!

shell4life
Post 3

@Perdido – You can cut all the pith off if you slice it right. You start by cutting off the top and bottom of the orange.

From there, you will have a good starting point. You will be able to see the fruit and the line where the pith starts.

Just position your knife perpendicular to the pith and start slicing downward. Follow the curve of the orange. If you miss some pith, it is so easy to go back and slice it off later.

Perdido
Post 2

Orange pith is so annoying. It's that white stuff that covers the actual fruit, and it seems impossible to peel all of it off.

It tastes bitter and just has a nasty texture. I usually peel an orange by hand, but even when I cut it into wedges and eat the fruit off of the rinds, I still have to be careful not to get a slice of pith in the mouthful of fruit.

Is there a good way to avoid pith when peeling an orange? Is there a certain way I should be slicing it?

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