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Prunus

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The genus *Prunus* is a diverse group of flowering trees and shrubs. It belongs to the Rosaceae family, which is commonly known as the rose family. This genus is very important because it includes many foods humans eat. These include plums, cherries, peaches, nectarines, apricots, and almonds. Collectively, these are often called stone fruit. There are approximately 340 accepted species within this genus.

01 Prunus sp.
01 Prunus sp.

Most *Prunus* plants produce a specific type of fruit called a drupe. A drupe is a fleshy fruit that contains a single hard shell. This fruit has several distinct layers. The fleshy outer part is called the mesocarp. This is the part that people usually eat. Inside the mesocarp is the endocarp, which is the hard shell. We often call this shell a "stone" or a "pit." The endocarp protects the seed, also known as the kernel, located inside. While some kernels are edible, such as sweet almonds, others are poisonous, like apricot kernels.

Scientists use different ways to classify these plants. Traditionally, researchers divided the genus into several subgenera based on physical traits. One famous system from 1940 by Alfred Rehder proposed six subgenera. These included *Amygdalus* for almonds and peaches, and *Cerasus* for true cherries. Other groups were *Prunus* for plums, *Padus* for bird cherries, and *Laurocerasus* for cherry laurels. *Lithocerasus* was also added to include bush cherries.

Nectarine Fruit Development
Nectarine Fruit Development

Modern science uses a different method called phylogenetic classification. This method looks at DNA and other sequences to see how plants are related. This newer research divides *Prunus* into three main subgenera. The first is *Subg. Padus*, which includes bird cherries and cherry laurels. The second is *Subg. Cerasus*, which contains true cherries like sweet and sour cherries. The third is *Subg. Prunus*. This large group contains many sections, including apricots, peaches, and various types of plums.

We can learn about the history of *Prunus* by looking at fossils. The oldest confirmed fossils of this genus date back to the Eocene epoch. These fossils have been found across the Northern Hemisphere. Some of the earliest specimens include wood, seeds, and leaves. These were found in the Princeton Chert of British Columbia, Canada. These fossils come from the Okanagan Highlands. This area was home to diverse forests about 52 million years ago.

Nectarine Fruit Development
Nectarine Fruit Development

Plants in the *Prunus* genus have many different physical features. Most species are either deciduous, meaning they lose leaves, or evergreen. Their leaves are usually simple and alternate. The flowers are often white, pink, or sometimes red. These flowers typically have five petals and five sepals. They can grow alone or in small groups called umbels or racemes.

01 Prunus sp.
01 Prunus sp.

Growing these plants can be difficult due to various pests and diseases. Some trees suffer from gummosis. This is a condition where gum leaks out of the bark. The tree produces this gum to respond to wounds from insects or disease. Another issue is black knot fungus, which is a major fungal disease in Northern America. Some species also face attacks from parasites like *Laetiporus gilbertsoni*. This is a brown rot parasite that affects decorative red-leaf plum trees on the Pacific coast.

Gummosis on an ornamental cherry
Gummosis on an ornamental cherry
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File:01 Prunus sp..jpg
01 Prunus sp..jpg
File:Gummosis on an ornamental cherry.JPG
Gummosis on an ornamental cherry.JPG
File:Nectarine Fruit Development.jpg
Nectarine Fruit Development.jpg
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