With their architectural shapes and feathery flower heads, thistles are easily recognisable to gardeners and non-gardeners alike. Although native to Europe, Mediterranean and Western Asia, they have found a niche in some gardens where they are grown for their tall silvery foliage and statuesque appearance.
Thistles are plants that can quickly become weeds and indeed many thistles are considered to be noxious weeds in parts of Australia. The scotch thistle, Onopordum acanthium, is the weedy thistle often seen in paddocks, wastelands or along roadsides. The so-called cotton thistle,Onopordum nervosum, is however only known in Australia as an ornamental garden plant.
Common name: Cotton thistle
Botanical name: Onopordum nervosum (also known as O. arabicum)
Description: This tall, upright plant is extremely prickly (the leaves and stem are prickly). It reaches a height of around 3m (10′) with a spread of about 1.8m (6′). It is striking for its size and the blue grey colour of its downy stem and wavy leaves. This thistle is a biennial, which means it takes more than a year to reach maturity so flowers in its second year after planting. The flowers are light purple tufts, rich in nectar, that are plentiful from late summer and autumn.
Climate: The cotton thistle will grow in most areas and can tolerate minimum temperatures down to -16deg.C.
Likes: Although this plant will grow in even the most difficult of conditions a more striking plant is grown if it is given the best garden conditions of:
full sun (will tolerate light shade)
Pests: Slugs and snails may cause damage to plants especially when they are young.
Weed status: Onopordum species have been noted as prohibited or noxious weeds in NSW, Tasmania, Victoria and Western Australia. The seed of all thistles may no longer be imported into Australia. For more information on weeds contact your local council or agriculture department.
1. Seeds: Onopordum nervosum grows readily from seed. Tip: To keep the plant from year to year collect a few seeds from your plant but remove other spent flowers to prevent excessive seeding.
2. Plants: Plants will be very difficult to find in nurseries. Limited supplies may be available from:
Red Cow Farm
Sutton Forest 2577
Phone: (02) 4868 1842
(The garden and nursery is open Mondays and Tuesdays. The garden is also open under Australia’s Open Garden Scheme on 25-26 April, 1998 11am-6pm Phone for other times or to make an appointment to visit.)
Mt Macedon Road
Mt Macedon 3441
Phone: (03) 5426 4144