Invaders such as purple-flowered Asian melastome and strawberry guava threaten to overrun delicate Hawaiian natives such as thornless roses and delicate tree ferns.
As a control she sliced the thorns off a second branch, but left the ants free to roam over it.After six weeks, she found that 45% of the leaves on the experimental branches showed signs of infection, compared with 14% of those (including the thornless controls) over which ants could roam freely.
The Eastern Desert receives sparse rainfall, but it supports a varied vegetation that includes tamarisk, acacia, and markh (a leafless, thornless tree with bare branches and slender twigs), as well as a great variety of thorny shrubs, small succulents, and aromatic herbs.
Others are variously known as knapweed, thornless thistle, cardo-del-valle, dusty miller, blue bottle, mountain bluet, sweet-sultan, hard heads, and Spanish buttons.
A most strikingly thorned American species is the cockspur hawthorn (C. crus-galli), with extremely long, slender thorns up to 8 cm (3 inches) long; a thornless variety is also available.
The branches are mainly thornless and have glossy dark green leaves and white flowers, occurring singly or clustered in the leaf axils.
The thornless remains are kept in the treasury at Notre-Dame Cathedral in Paris.
Glen Ample bears large crops of delicious fruit; Glen Moy has thornless canes bearing large firm fruit early in the season; Glen Prosen is also thornless but needs good soil to produce the best crops; Tulameen has a superb flavour.
Fiona's third choice of unusual plants worth trying was the jostaberry (£7.50), a cross between a gooseberry and a blackcurrant, but thornless.
She imagines swooning in his arms like some gauzy thirties film starlet, propped up on a blue powder puff and surrounded by thornless roses as he tells her he loves her.
The bushes are thornless.
