Red Alder, Large Trees
- American tree, grows v. fast, loves wet sites, adds nitrogen to soil, big catkins.
- Saplings & Standards.
- Big red catkins, early pollen for bees.
- Max. Height: 20+m
- Bareroot Delivery: Nov-Mar.
Alnus rubra: Bareroot Red Alder Trees in Standard Sizes
Red Alder trees, Alnus rubra, is a slender, elegant tree with a neat, cone-shaped canopy. Unlike other Alders, it doesn't tend to produce suckers. It is quite decorative in spring, when the bare branches are festooned with long red catkins. It gets its name from these catkins and from its wood, which flushes red when a fresh piece is split and exposed to the air. The green leaves are crinkled and serrated, turning mid-yellow in autumn.
The tallest Red Alder on record was 32 metres tall, but 20 metres is typical.
Delivery season: Alders are delivered bareroot during late autumn and winter, approximately November-March inclusive.
Choosing a size: Small trees are cheaper, easier to handle and more forgiving of less than ideal aftercare, so they are best for a big planting project. If instant impact is your priority, or if you are only buying a few plants for use in a place where it is convenient to water them well in their first year, then you may as well use bigger ones. All our bareroot trees are measured by their height in centimetres above the ground (the roots aren't measured).
- Height: 20m
- Soil: Any, ideal for poor & wet sites. Needs full sun.
- Grows on the coast
- Use: Screening, reclaiming, erosion prevention
- Adds nitrogen to soil. Big catkins.
- Colour: Yellow Autumn leaves
- Bareroot delivery only: November-March
Growing Red Alder
They will grow vigorously in very wet soil, but they do need full sun. They prefer lighter, sandier soils to heavy clay, but only chalk is a problem. They will also grow on the coast.
They are very tough trees, but urban pollution tends to cause cosmetic damage to their leaves.
Note: Alders have invasive roots that can break old water pipes and damage the foundations of old buildings or walls. 15 metres away from vulnerable structures is a safe distance. New build, concrete foundations are not at risk.
Did You Know?
Red Alder is native to the West coast of America, where it is also known as Oregon or Californian Alder, and is the traditional wood for smoking salmon. It was introduced to Britain in the late 1800's. The wood is good for making string instruments, especially electric guitars and basses.
Like the rest of the Alder family, it has symbiotic bacteria living in nodules on its roots that improve the soil by releasing water-soluble nitrogen based compounds. Alders are especially useful for quickly binding loose, rocky soil.
Standard trees are measured by their girth in centimetres 1 metre above ground level: their trunk's waist measurement. Unlike sapling trees and hedge plants, standards aren't measured by their height, which will vary quite a bit both between and within species.
So, a 6/8cm standard tree has a trunk with a circumference of 6-8cm and an 8/10 standard has a trunk 8-10cm around. This measurement makes no difference to the tree's final height.
On average, standard trees are 2-3.5 metres tall when they arrive, but we cannot tell you precisely how tall your trees will be before we deliver them.
Notes on planting Red Alder trees:
Red Alder trees need a sunny site with moist or wet soil. They prefer rich, heavy clay, but they will also grow on very poor, degraded soils. They will grow near the sea and although they are hardy across Britain, they aren't ideal for exposed sites or frost pockets in the North-East, where they will probably suffer some damage from late spring frosts. Common Alder and Grey Alder are the hardiest of the group.
Red Alder will not grow in the shade or on chalk.
Prepare your site before planting:
It is good to dig over the site where you plant a tree several months in advance. Kill the weeds first: for tough weeds like nettles, brambles and ground elder, you will usually need a weed-killer to get rid of them. When you dig the soil over, remove stones and other rubbish and mix in well rotted compost or manure down to the depth of about 2 spades.
Watch our video on how to plant a tree for full instructions.
Remember to water establishing trees during dry weather for at least a year after planting.
Tree Planting accessories:
Prepare your site for planting by killing the weeds and grass with Neudorff WeedFree Plus. You can buy a tree planting pack with a wooden stake & rubber tie to support the tree and a mulch mat with pegs to protect the soil around the base of your tree from weeds and drying out. We suggest that you use mycorrhizal "friendly fungi" on the roots of all newly planted large trees: if your soil quality is poor, we strongly recommend it.
After you plant a tree, the most important thing to do is water it in dry weather. You will also need to weed around the plants. Watering should be thorough, so the ground is soaked. Let the soil almost dry out before watering again. Watering & weeding will be necessary for at least a year after planting.
If your trees do need pruning, it is ideal to do this in winter. Always hire a tree surgeon to remove large branches.
Special notes on caring for Red Alder trees:
Red Alder is a very tough tree that shouldn't need special attention once it has established.
Hygiene & Diseases:
Dead, damaged or diseased wood can be pruned off as soon as it appears.
Disinfect your pruning tools between every cut if there is any sign of disease.
Burn or dispose of any diseased material, do not compost it.