Agave filifera aka Thread Agave

Agave filifera is an evergreen succulent known as thread agave. It belongs to the asparagus family, Asparagaceae. Kew places its native range in central Mexico, from Querétaro to México State. It grows in a subtropical climate. Gardeners grow it mainly for its dense leaf rosettes. These form a low mound without a trunk. The RHS gives a height of about 1.5 feet [0.45 metres]. Its listed garden size reaches 1.6 feet [0.5 metres] tall and wide. Other accounts give widths up to 2.1 feet [0.65 metres].

The stiff leaves spread out and curve slightly upward. They have a dark green surface and a leathery feel. Thin white threads peel away from the leaf edges. White marks from nearby buds also cross the leaf surface. Each leaf ends in a strong, sharp spine. The spine starts brown and turns grey with age. Most leaves measure 0.5–1 foot [0.15–0.30 metres] long. Some reach 1.3 feet [0.40 metres]. New shoots grow from the base and form more rosettes.

Flower stems rise far above the low leaf mound. They can reach 8.2 feet [2.5 metres] in height. Dense groups of bell-shaped flowers fill the upper stem. The RHS describes their colour as greenish white. LLIFLE reports that green flowers turn red as they age. Chicago Botanic Garden lists red blooms from November through April. Its record concerns a plant grown in a greenhouse. The main rosette dies after flowering, while basal shoots can continue growing.

Both the RHS and Chicago Botanic Garden list full sun. Under glass, the RHS advises strong light filtered from direct rays. Use cactus compost or soil with good drainage. The RHS lists sand and loam, with acid or neutral pH. Give moderate water during growth and very little in winter. Feed growing plants every two to three weeks with balanced liquid fertiliser. Hardiness reports differ: Chicago lists USDA zones 8–11. The RHS assigns H2, which calls for protection from freezing. The RHS gives a maturity period of ten to twenty years.

Its firm shape suits gravel gardens and small courtyards. It also serves as a specimen in coastal or Mediterranean-style planting. No routine pruning is needed. Take offsets in spring or autumn to raise new plants. Scale insects may attack, though the RHS reports few disease problems. Contact can irritate human skin, so wear gloves when handling. The RHS also warns that eating it can harm dogs and cats.