Fresno: Characteristic and caring tips

Few things are more pleasant than a walk among large shady trees. Ash has always been a very well known and valued species throughout the world, even those who have no knowledge of botany.

We are talking about a tree that, over many years, can reach up to 20 meters in height, with a majestic bearing and a very thick trunk. The ash genus ( Fraxinus ) includes up to 60 species of trees classified according to their identification and growth zone.

For example, we find the European ash or common ash ( Fraxinus excelsior ), the narrow-leaved ash ( Fraxinus angustifolia ), and the great American representatives that we can find in many areas of North America, such as Fraxinus americana or Fraxinus pennsylvanica.

In this plant sheet we are going to tell you the most interesting points of this tree, as well as its care from transplanting to making it an adult specimen.

Seeds and leaves of common ash (Fraxinus excelsior)



Ash is a fairly common tree that has been distributed almost all over the world. In fact, it is a way of classifying it. We find the marvelous American, European and Asian ash trees (Eastern Palearctic), with quite notable differences between them, although respecting the common points of leaf shape, color, height and characteristics of the trunk.

In general, when they are adults, they usually have a height between 15 and 20 m. They have a straight trunk and not twisted at all, with a dark brown color. As with other species, such as palm trees , ash is dioecious . This means that each individual is represented by a single sex, being able to find different male and female specimens. Therefore, for their pollination and fertilization (production of seeds), it is necessary that male and female specimens are grouped and relatively close.

Another curiosity of the ash is that the seeds, after fertilization, are contained in a samara , a kind of flattened and light tissue that, due to its shape, favors dispersion through the wind when it falls from great heights.


The planting of ash in parks and gardens is mainly of ornamental interest . A good-looking tree, with a fairly horizontal structure of stems and branches in the crown that guarantees a large area of ​​shade.

On the other hand, its timber use is also very interesting , since we are talking about a high density wood 670 kg / m to 710 kg / m³, which varies with each species. European ash has a somewhat denser wood than American, where the latter is widely used in North America to manufacture furniture, tools and sports equipment (baseball bats).

At an environmental level , ash trees are a great ally in the ecosystem, forming part of the diet of wildlife species, which have a predilection for their leaves. When its wood cracks, it forms holes that serve as shelter for numerous species such as birds and small mammals.


Although there are about 60 species within the genus Fresno ( Fraxinus ), the largest representatives of this group are the following:

  • White ash ( Fraxinus americana )
  • Fresno negro (Fraxinus nigra)
  • Fresno verde (Fraxinus pennsylvanica)
  • Blue Fresno ( Fraxinus quadrangulata )
  • Narrow-leaved ash ( Fraxinus angustifolia )
  • Fresno común (Fraxinus excelsior)

Left: Common ash ( Fraxinus excelsior ). Right: White ash ( Fraxinus americana )



Ash is a deciduous tree, where it loses its leaves in autumn, faster in cold climates. This makes it very well adapted to all types of climates, from hot to cold. Its usual zone is temperate. The best visual representation of this species is when, in autumn, its leaves turn reddish and orange before falling, they form a very attractive landscape in forests, parks and gardens.

In spring, it restarts the cycle and sprouts again with force, where some species combine the leaves and flowering at the same time.


It adapts very well to all types of soils, preferring those loose, fresh and that retain moisture well. To achieve these variables, it usually requires a soil with a high percentage of organic matter.

This is the norm in deciduous forests such as ash, where the leaves are slowly composting until they form a very interesting plant organic matter to provide energy in the future spring sprouting.


Irrigation and water supply care is reserved for young species in the first years of life. On average, a young species can carry out each irrigation with between 5 and 10 L, allowing the water to infiltrate well and avoiding stagnant water around the trunk.

In general, 2 or 3 waterings in summer, depending on the average temperatures, and 1 watering every 15 days in winter, 2 if this season is mild in temperatures.


The most practical way to maintain a continuous supply of nutrients in the first years of life of the ash tree is through organic matter. We will contribute at the beginning, in the planting hole, between 5 and 10 kg of vegetable compost or animal organic matter, well decomposed and mixed with the earth.

Every 2 years, we will return to contribute 5 kg around the trunk, which will release nutrients according to the environmental humidity and the contribution of irrigation.

On the other hand, if we want to make it grow as quickly as possible, the contribution of inorganic fertilizers at the beginning of spring, coinciding with flowering, can be interesting.

To do this, the most comfortable way is to add granulated NPK fertilizer and micronutrients , in an amount of 200 to 400 grams, around the main trunk, repeating the operation in summer.



Any of these 3 formulas is valid and provides enough nitrogen to activate budding with the arrival of spring: greater light and gradual increase in temperatures.


the usual multiplication of this tree is done by seeds. Being a rustic species, its seeds are quite viable and can germinate without stratification. However, to ensure the highest germination rate, they usually require a small layering:

  • Stratification for 2 to 3 months at a temperature between 15 and 20 ºC, and another for 3 to 4 months at 4-5 ºC on its own substrate, maintaining constant humidity.


Main pests

As is currently happening with the pine processionary, the red palm weevil or the elm galeruca, there are pests that mainly attack a species or genus of plants, and trees are the most affected, due to the difficulty of carrying out treatments.

In the case of ash, there is a type of wood-dwelling beetle of this species. Its scientific name is Agrilus planipennis,  and it is affecting millions of ash trees distributed mainly throughout North America.

In fact, its importance has grown in recent years to become an environmental concern. Timber transport bans have been established, something complicated in these North American countries since their timber is widely used.

Main diseases

Depending on the humidity zones where the representatives of the genus Fraxinus live , they may have symptoms of root rot (excess moisture in the soil) or anthracnose, with deformations in the trunk.

In general, these types of diseases that affect both the roots and the aerial part, are typical of very humid areas, such as in the ash forests of Scotland.


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