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Thorns, Spines and Prickles

Did you know plants have their own mechanical defences?

Some of them can cause severe discomfort and even pain.

If you get pricked by a thorn, spine or prickle, clean it immediately and watch for infection.

There is something called "Plant Thorn Arthritis" which I will write about soon in another page.

In the meantime, here's what you need to know.

How to Tell the Difference
Between Thorns,
Spines
and Prickles

THORNS

THORNS are shoots or modified stems with very sharp, woody points and appear immediately above a leaf.. or where a leaf would be and each thorn contains a "vascular bundle" (see sketch) -

These are some trees and shrubs that have THORNS.

Hawthorn (Crataegus monogyna),

Quince (Cydonia oblonga),

Buckthorn (Rhamnus cathartica or Frangula alnus) or

Honey-Locust (Gleditsia triacanthos)

WHY?: they form a mechanical protection from plant eaters

Thorn Sketch

WHAT'S A VASCULAR BUNDLE?

It's part of a transport system of tube-like tissues that run through the plant carrying water and nutrition to different parts of the plant..

- shown with red lines in the sketch above, they go up the stem and out the length of the thorn.

Vascular bundles are those dots you see when you cut a piece of celery (sketch below).

Hawthorn Thorns

Quince Thorn

Buckthorn Thorn

Honey Locust Thorns

WHAT ARE SPINES ?

SPINES are sharp, pointed modified leaves that form spikes as the plant evolves, replacing the leaves - especially in plants living in dry conditions like Cacti - as the spines help reduce water loss.

Spines appear in the position of a leaf, just below an axillary bud They also contain vascular bundles and are found in:

Barberry (Berberis)

Black Locust (Robinia pseudo acacia)

FUNCTION: mechanical protection as well as preventing excessive transpiration in plants like Cacti.

SPINE SKETCH

Black Locust Spines

Barberry Spines

Cactus Spine Sketch

WHAT ARE PRICKLES ?

PRICKLES are modified hairs (epidermis) that are sharp, woody outgrowths on the stem or cane of a plant but unlike thorns and spines, prickles do not contain vascular bundles.

They are extensions of the plant cortex and epidermis (outer layer of the stem) and are neither modified stems nor leaves
They are also easy to remove without damaging the stem or cane

FUNCTION:
- protection

- like grappling hooks for stems to climb over neighbouring objects like trellises or trees

LOCATED: anywhere on the twig or cane

Roses (Rosa)

Blackberries. Raspberries (Rubus)

Rose Prickles Sketch