Thorns, spikes and prickles are all hard, pointy extensions that grow on a plant's leaves or stems, and sometimes both. Gardeners often use the terms "thorn" and "prickle" interchangeably. However, if you talk to a botanist or horticulturalist and call a thorn a prickle, you may be corrected. There are distinctions between thorns, spikes and prickles.
From a biological perspective, a thorn is actually a modified branch or stem on a plant. Thorns can be thought of as "hang nails" on plants. Thorns can scratch or puncture your skin enough to make it bleed. There are two main species of plants that have thorns. What may come as a surprise to some is that roses are members of neither species. The luscious lemon is used to make a jug of lemonade or to garnish seafood and other foods. It grows on a branch with thorns on its twigs. Popular varieties include the slightly thorny Meyer lemon, the mildly thorny Ponderosa and the very thorny Rough Lemon. The second genus of thorny plants is Carissa. The plants grow as evergreen shrubs and trees with starlike flowers, reminiscent of jasmine. Carissa grow natively in tropical climates of Australia and Africa. and its flowers attract birds and butterflies. After the flowers die, they bear bright scarlet-coloured edible fruits. Carissa is grown as a hedge shrub. Cultivars include Carissa macrocarpa 'Big Num-Num,' Carissa amantungulu -- whose common name Is Natal Plum -- and Carissa bispinosa, which is commonly referred to as 'Num-Num' and grows natively in South Africa.
Prickles are to plants what hairs are to humans. Prickles grow on the outer layer of a plant's stem. The coarse nature of prickles often makes people confuse them with thorns. That's the case with roses. While people refer to them as "thorny," rose stems are actually "prickly," from a biological standpoint. One of the prickliest roses in the family is even named the prickly wild rose (Rosa acicularis). This rose grows as a bushy shrub and can be raised in home gardens or found naturally in forests and along riverbanks. Cacti are also characterised as prickly plants.
The word "spikes" is more of a horticultural term than a biological word. Flowers are often referred to as having "spikes." Clethna alnifolia 'Hummingbird' is one such plant. It's a summer-flowering shrub with fragrant flowers that grow on the plant's long spikelike stem, attracting butterflies and hummingbirds to its nectar. Another favourite is Hosta ventricosa, a hardy herbaceous shade-loving perennial that blooms with spikes of violet-blue flowers from May to July. Then there's the Tylecodon reticulates, a succulent bonsai originally from Africa, with spikes of flat tubular leaves that grow from stalklike shoots that resemble ginger root.
Anyone Interested in thorny, spiky or prickly plants may also want to consider spiny plants. Biologists actually reference plants with "spines" more often than plants that have "spikes." Spines are modifications in the structure of the plant's leaves. Thistle, Ilex and Berberis are examples of plants that have spines. Spines can be as treacherous as thorns. For example, the Artichoke Thistle (Cyara cardunculus) is considered an invasive weed. Its sharp spines set up an impenetrable barrier, crowding out plants in the wild, animals and humans.