Planting Guide: How to plant, grow and care for your Arum
What is an Arum?
Arum is a genus of flowering plants in the family Araceae, native to Europe, northern Africa, and western and central Asia, with the highest species diversity in the Mediterranean region.
They are tuberous, herbaceous perennial plants growing to 20–120 cm tall, with sagittate (arrowhead-shaped) leaves 10–55 cm long. The flowers are produced in a spadix, surrounded by a 10–40 cm long, distinctively coloured spathe, which may be white, yellow, brown, or purple. Some species are scented, others not. When ripe the fruit is a cluster of bright orange or red berries.
All parts of the plants, including the berries, are poisonous, containing calcium oxalate as raphides. Animals tend to avoid them.
The genus name is the Latinized form of the Greek name for these plants, aron.
In the Southern Hemisphere Arums flower from May until November. The flowers are very small and rarely visible. The flowers are borne on a poker-shaped inflorescence called a spadix, which is partially enclosed in a spathe or leaf-like hood of varying colour. The flowers are hidden from sight, clustered at the base of the spadix with a ring of female flowers at the bottom and a ring of male flowers above them.
After the inflorescence opens, the spadix heats up well above ambient temperature, due to a phenomenon called thermogenesis. This is caused by the rapid consumption of starch in cyanide insensitive respiration, which is biochemically different from the respiration normally found in plants. The heat is used to vaporize odour components, which in species with short “flower-stalks” cause a faecal smell. This in turn attracts the small flies and gnats that are to be trapped within the inflorescence.
As the time required for successful pollination to occur can be several days, many of the small insects nevertheless die within the flower due to their short lifespan. No digestive enzymes or similar components are present; and in fact, once pollinated, the entire inflorescence starts withering except the central part, from which the berries later emerge.
Arums have no strong scent.
Arum Growing conditions
Foliage is at its best in light shade, while the red berries are most spectacular with more sun. This plant thrives in moist conditions. Water during dry spells, and then reduce water when leaves begin to wither.
Fertilizer/Soil and pH:
Grow in soil rich in organic matter with a slightly acid to neutral pH (6.5 to 7.0). A balanced fertilizer can be applied monthly during active growth.
Arums seldom have disease or pest problems, and the foliage is resistant to damage by both slugs and deer. All parts of the plant are toxic and animals do not tend to graze them.
The flowers are insignificant and are rarely seen. At flowering time the plant sends up a spathe and spadix (which carries the flowers). The spathe and spadix are obvious when compared to the leaves.
Divide clumps of tubers in summer when plants are dormant. No further attention is required.
Withering leaves may be removed in late spring and it is at this time that the tubers are left in the ground/pot for next year.
The lifecycle of Arum
Arums, generally, are a common woodland plant. Although the leaves emerge in April they can take until June to fully emerge. They should be grown for the leaves in their own right.
If you are having a walk in a local woodland look down at ground level and spot these striking pale green sheath-like leaves wrapping round a purple or sometimes yellow needle-like structure or spadix as it is known. The sheath-like leaf or spathe is not the flower it is actually a modified leaf which curls around the spadix and then hidden from view, at the base of the spadix, are finally the tiny flowers, first the male flowers then many clusters of female flowers. The role of the spadix is to give off a smell of decay but also amazingly it gives off heat which together attracts pollinators. If you gently, carefully, touch the spadix you can feel this warmth! Remember that all parts of the plant are toxic and may cause an allergic reaction.
The preferred pollinators are midges, usually female and visiting at night. Before the midges can reach the flowers they pass through a ring of hairs which then trap them in the base of the structure and keep them in there for several hours while they pollinate the flowers and enjoy the warmth! This ability for some plants to regulate heat is known as thermogenesis and has been fascinating scientists for years. For example Arum maculatum can raise it’s temperature if covered in snow to melt it which then allows the leaves to come through. An intriguing capability!
The plant also contains oxalate crystals which are released if the plant is damaged. They act as an irritant to skin, the sensation has been described as feeling like ‘many small needles being broken into the skin’, therefore this plant is not recommended as natural toilet paper if you are ever caught short!
By autumn the flower spike has transformed into the familiar stalk of red berries you might spot on the woodland floor. This total transformation is another captivating quality of this plant. There is another variegated version of this plant (Arum italicum)which you might see alongside the more common Arum maculatum in England. See if you can spot both species and the differences in the spathe and spadix!
How to plant Arum?
All true Arums should be planted with a covering of 2-3cm of potting mix/soil. The tuber will pull itself down to where it will take control.
How to grow Arum?
Arums can be gross feeders and so appreciate a highly fertile environment. At Elite Bulbs we fertilise every two or three weeks. They can be planted in any fertile place and let go. They will do alright in poor soils but excel when loved. While Arum maculatum and Arum italicum come from the United Kingdom there are many other species that come from Europe.
How to care for Arum?
Arums are low maintenance. No matter what the conditions as long as they are kept damp. By summer the tubers will have pulled themselves down far enough that they will survive. They are a plant that requires very little care.
- Arums are incredibly easy to grow
- They require a moist (never dry out while growing) environment to do well.
- The color of the spathe can be white, yellow, spotted, and purple.
- Arums can be grown for their foliage.