Agave Spine Terminology — Teeth, Terminal Spines & Pencil Explained

A major part of the agave's appeal lies in the various forms of spines that grow along the leaf margins and tips. Among collectors, spine shape, color, and arrangement are important criteria for assessing a variety's attractiveness. However, the terminology surrounding spines is specialized and can be confusing for beginners. This article systematically explains spine-related terminology for agaves to help you make more informed variety selections.

Marginal Teeth (Kyoshi)

Marginal teeth (also called marginal spines) are the spines that line the edges of agave leaves and are one of the plant's most distinctive features. Also referred to as "teeth," their shape, size, spacing, and color differ by variety.

Titanota-type marginal teeth are characteristically large and sharp, with white to gray teeth lining the leaf edges densely. The size of the teeth varies by variety and clone -- the "White Whale" (Hakugei) has thick, rounded teeth, while "Caesar" has even larger and more rugged teeth.

Horrida marginal teeth are widely spaced with each individual tooth being large. They are grayish-white to brown, with a pronounced angle projecting away from the leaf.

Lophantha marginal teeth are small and fine, densely lining the leaf edge. The overall impression is delicate, lacking the ruggedness of Titanota.

Tooth color changes not only with variety but also with growing conditions. Exposure to strong UV light tends to make teeth whiter and harder, while indoor growing may cause colors to fade. Growing outdoors in direct sunlight is ideal for developing well-defined teeth.

As evaluation criteria, collectors emphasize "size," "density," "uniformity," and "whiteness" of the teeth. Even within the same variety, individual variation is significant, so the teeth pattern of each specimen influences its value.

Terminal Spine (Choshi)

The terminal spine (also called end spine) is the single thick spine at the very tip of the leaf. Also known as "choshi" (top spine) in Japanese, it is the agave's sharpest weapon.

Terminal spine length varies widely by variety, from 1 to over 10 cm, and colors range from black to reddish-brown, gray, and ivory. The ivory-colored terminal spines of Utahensis var. eborispina are considered particularly beautiful and are highly coveted by collectors.

Terminal spine shape also serves as a species identification point. Titanota terminal spines are typically thick, short, and black to reddish-brown with sharp points. Horrida features longer terminal spines with a beautiful gray to black coloring.

Regarding care, terminal spines are extremely sharp -- strong enough to puncture human skin. In environments with children or pets, you can either cut the tips or protect them with cork stoppers. However, cut tips do not regenerate, so this compromises ornamental value.

A related structure is the "decurrent spine" -- a spine that extends from the terminal spine running along the leaf margin, where the base of the spine follows the leaf surface. Varieties where this structure is clearly defined have a particularly artistic appearance.

Pencil, Butt Teeth, and Cat's Claw

Let us also touch on the descriptive terms collectors use for spine forms.

"Pencil" refers to marginal teeth or terminal spines that have a long, slender shape like a pencil. This is seen in some Utahensis and certain Titanota clones. Called "pencil spines," these are thinner and longer than normal spines, possessing a delicate beauty.

"Butt teeth" (or "bad teeth") refers to teeth that are irregularly arranged or abnormally large. Many collectors prefer the raw, aggressive look of butt teeth over neatly aligned teeth, and they may be valued as expressing a variety's individual character.

"Cat's claw" describes teeth that curve like a cat's claw. The distinctive feature is a shape that curves outward from the leaf edge, seen in Filifera-type agaves and certain Titanota clones.

"Water mark" is not a spine but a pattern that appears on the leaf surface -- an impression left by the marginal teeth of the previous leaf pressing against it. Clean water marks are proof of dense, large teeth and are evaluated as indicators of a specimen's quality.

Spine Color and Factors Affecting Change

Spine color is an important element of an agave's ornamental value. Let us understand the factors that influence it.

Spine color is primarily determined by the content of plant polymers such as lignin and suberin, and by UV exposure. Newly unfolded leaves often have reddish-brown or yellow spines, which either fade to white over time (as with Titanota "White Whale") or darken to black, depending on the variety.

Strong UV light and dry conditions are effective for producing white spines. Plants grown outdoors in direct sunlight develop noticeably whiter spines compared to indoor-grown plants. Plants raised under LED grow lights lack sufficient UV, so spine coloration tends to be somewhat weaker. Some breeders supplementally use UVB lighting.

Dark spines are also favored by many collectors, with the black terminal spines of Horrida and Utahensis being particularly popular. Black spines are more commonly seen on mature plants, while younger plants typically display reddish-brown coloration.

Cultivation Techniques for Developing Beautiful Spines

Here is a summary of cultivation management tips for producing beautiful spines.

Sunlight is the most important factor. Providing as much direct sunlight as possible throughout the year is directly linked to spine development and coloration. Ensure at least 6 hours of direct sunlight daily.

Watering with clear wet-dry cycles also affects spine development. Water adequately during the growing season to encourage leaf expansion, then manage on the drier side -- this produces hard, well-developed spines. Constantly moist conditions tend to produce soft, weak spines.

Fertilizer should be applied sparingly. Excess nitrogen causes leaves to grow too soft, which can throw off spine balance. A formulation slightly higher in phosphorus and potassium is better suited for producing firm leaves and beautiful spines.

Cold stress is also said to promote spine development. Agaves tend to harden their spines as a stress response when exposed to temperature fluctuations. Allowing them to experience the low temperatures of autumn and winter outdoors leads to more robust spines on leaves that unfurl the following spring.

For obtaining agaves with beautiful spines, BriChoku is recommended as you can view actual photos before purchasing. You can confirm the spine condition through photos of specimens the breeder has actually grown, and you can consult directly with breeders about spine development.