Alder (Alnus)

The leaves of the alder are deciduous

With the name of alder About thirty species of trees and shrubs are known to be cultivated in practically all temperate regions of the world. And it is that being able to resist frost, and to become beautiful in autumn before dropping its leaves, they are very, very interesting plants.

Do we know them? If you would like to have one in your garden, you can't stop reading 🙂.

Origin and characteristics

The Alnus glutinosa or alder forms forests

glutinous alnus.
Image - Wikimedia / Willow

Alder it can be a deciduous tree or shrub that lives in temperate zones of the world, mainly Europe and America. Its leaves are ovate, with serrated or serrated edges, green in color except in autumn when they turn yellow before falling. The flowers are catkins: the female ones are short, and the male ones elongated, both found on the same plant.

The main species are:

  • alnus cordata: known as Neapolitan alder, it is a native tree of southern Italy that reaches between 17 and 25cm in height.
  • glutinous alnus: it is the common alder or black alder. Often called simply as alder or alno. It grows to a height of between 20 and 30 meters, and is native to Europe and Southwest Asia.
  • alnus incana: it is called gray alder or gray alder. It grows in the coldest regions of the northern hemisphere, reaching 15-20 meters in height.

What are their cares?

The Alnus or alder usually blooms in spring

If you want to have a copy of Alnus, we recommend you take care of it as follows:


Must be outside, in full sun. Put it at a minimum distance of 7-8 meters from pipes and others because its roots can be invasive.


  • the garden: grows in deep, cool, and slightly acidic soils. It does not tolerate limestone.
  • Flower pot: It is not a plant that should be kept in a container for a long time, but while it is young there will not be too much problem. Use acidic plant substrate (such as this).


The alder is a plant that lives near waterways. In fact, you will always find it on riverbanks and similar sites, therefore, it is very important that you water often. What's more, if you have grass, plant it in it if you can put it at a distance of at least 7-8m from the pipes and others. In case you don't have it, don't worry: you will simply have to water it very often: daily during the warmest season of the year, and every 2-3 days the rest of the year.

If you are going to grow it in a pot for a while, put a plate under it if you want and fill it up every time you see that it is running out of water. Use rainwater or lime-free. If you only have the option of watering with the tap and it is calcareous, dilute the liquid of half a lemon in 1l of the precious liquid, or a tablespoon of vinegar in 5l / water.


From early spring to late summer (or until autumn if you live in a warm-temperate climate where the frosts are late or of little importance) it is advisable to pay it once a month with ecological fertilizers. Here you have a list of those that are recommended to use.


View of the leaves of Alnus incana

alnus incana
Image - Wikimedia / Franz Xaver

It multiplies by seeds in autumn or spring, and by semi-woody cuttings in spring. Let's see how to proceed in each case:


The step by step to follow is as follows:

  1. The first step is to fill a forest seedling tray or pot with acidic plant substrate, and water thoroughly.
  2. Then, the seeds are sown, ensuring that they are a little separated from each other. The ideal is not to put more than 2 in each socket or pot, since otherwise if they all germinate it would be very difficult to separate them successfully.
  3. They are then covered with a thin layer of substrate.
  4. Finally, sprinkle copper or sulfur, water a little more with the sprayer, and place the seedbed outside.

Thus, they will germinate in 1-2 months.

Semi-woody cuttings

To multiply the alder by cuttings, you just have to cut a piece of semi-soft wood branch about 40cm in length, impregnate the base with homemade rooters or rooting hormones, and plant it in a pot with a growing substrate for acidic plants.

If all goes well, it will root after about 1 month.


It depends on the species, but in general resists cold and frost down to -14ºC. It cannot live in tropical or subtropical climates.

What uses does it have?

The leaves of the Alnus firma are smaller than those of other species

Alnus signature
Image - Wikimedia / Michael Wolf


Alder it is a very decorative plant and relatively easy to care for. It is used as screen hedges, windbreaks, isolated specimen or planted in groups ... It looks great anywhere.


  • Leaves:
    • Freshly picked: they are flattened and placed under the soles of the feet with the socks. Helps relieve pain and stop sweating from them.
    • Shredded: in a poultice, they serve to accelerate wound healing, and to provoke the milk retina in pregnant women.
  • Cortex: once cooked, the resulting liquid is used to gargle that will help to harden the gums, heal sore throats and sore throats.

Other uses

It is used for the manufacture of paper, boxes, plywood, sculpture or panels.

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