For sheer size and quickness of growth, there are few - if any - ornamental grasses that can compete with Arundo donax.
The one in the image below, has put on that much growth - around 2 metres - in three or four months. It dies down each Autumn - only to re-emerge again in the Spring and soon gets to is ultimate height of around 3 metres. It is often mistaken for a bamboo, and of course the bamboos are of the same family as the grasses.
If you plant one of the Arundo grasses in your garden, then you will most certainly have discussions with visitors as to whether or not it really is a grass or a bamboo. It IS a grass, even if it does grow the height of many bamboos.
I have planted these in many schemes and the client has always been amazed at its speed of growth.
It will most certainly reach a height of 2 metres of more each year - starting from the ground level to which it dies back each Autumn.
Arundo donax is hardy in all but the most severest of winters - especially after establishing for a few years.
If there are any worries, then it is easy to take cuttings from this grass in mid summer (see below) , and grow a few in pots in the cold greenhouse or store in a garage for the coldest of winter months.
The small Arundo
plants, planted out in the spring will soon get to the size of the one
in the image.
They rarely flower. No matter. They are a splendid sight just for the foliage alone. They will die down each Autumn - leaving a still attractive clump of straw coloured foliage. This should be cut back to just above ground level in the spring.
Arundo donax Variegata; A. d. Variegata Superba; A. d. variegata var.
Versicolor, should all be assumed to be only half hardy, and will need
protection during winter months.
This protection might well just be a good covering of straw in lass severe areas, or digging up and planting in a container - or heavy duty plastic bag and moved to a relatively frost fee area such as cold greenhouse or even garage for the winter months.
Again, they can be propagated easily as below.
This variegated form has superbly marked white stripe variegations, and is the ideal plant for a large container. This container can either be shown off on a sunny patio, or plunged into the garden soil, and lifted up each Autumn to spend the winter in safety!
Arundo can be divided just as the new growth is appearing in spring.
It will require a couple of hefty garden forks to do this, or you can
simply part a few side growths away from the main clump.
Cuttings are also possible - but not the normal tip cutting. Simply cut a section of the stem (8-12in long) away from the main plant in early to mid summer, strip it of any lateral leaves and either lay it on compost with a propagator top over it. Place in a warm situation. Alternatively, the stem cutting can be rooted in water - either in a large jar, or in a tray of water!
Arondo do not suffer from any pests or diseases. It is happiest in a moist soil and sunny situation, but will grow in almost any garden soil. Avoid windy situations, simply because of the height it will reach annually. Having said that, they are superb when flowing in a breeze or light wind, and are generally unscathed in non-persistent strong winds.
Basically. Plant and enjoy!