Agave havardiana

Agave havardiana, or Havard's Agave, native to the limestone and semi-desert mountains in the central part of northern Mexico, is one of the hardiest of its genus. In dry soil, it can withstand temperatures as low as -23°C (-9.4°F), and will survive our winters at -17°C (1.4°F) as long as it is protected from rain. This perennial plant slowly forms an open rosette of medium size, with regularly arranged, toothed, bluish-grey leaves. The flowering emerges from the centre of the older rosettes, signifying the death of the plant that has taken care to produce suckers near its stump. With its fierce armour that requires some distance from high-traffic areas, it possesses a unique architectural presence that can be enjoyed in a large rock garden, on a slope, or in an elevated bed, in most regions.

Agave havardiana, discovered in 1912, is a botanical species with very slow growth that is adapted to most climates, provided it is planted in soil rich in rocks and coarse sand, with good drainage. It belongs to the Asparagaceae family (formerly Agavaceae), just like yuccas and tuberose. This herbaceous perennial succulent has rhizomes capable of producing suckers, but it reproduces more easily through its seeds than by producing daughter rosettes. It is almost devoid of aerial stems. Its open but well-developed rosette will reach an average height of 50cm (20in) and a diameter of 70cm (28in) at maturity. It is composed of grey-blue to grey-green leaves and has a characteristic shape: they are wide at the base, widen halfway up, and taper towards their tips. Each leaf ends in a long spine measuring 3 to 6cm (1 to 2in) in length, and is brown-black in colour. They are rather flat, not very thick, and have regularly spaced teeth, grey-brown to reddish in young plants. When a rosette is mature, after many years, it produces a flowering stem that can reach up to 3m (10ft) in height. It bears some horizontal branching. The branches carry flat and spherical panicles. The rosette, classified as semelparous, dies after flowering, which lasts several months. While Agave havardiana does not often produce suckers in nature, the few subjects that multiply in this way have been selected and widely spread in cultivation. Thus, it is not uncommon for the plant to be surrounded by daughter rosettes from the first years of cultivation.

This very hardy agave will find its place in a large rock garden, a south-facing slope, or at the edges of a dry garden, where its remarkably architectural silhouette will stand out in a mineral and minimalist setting, punctuated by some wild grasses such as Stipa ichu or Stipa gigantea. It can be planted with Prickly Pear and other Opuntias, Giant Fennel, and fairly hardy columnar cacti (Cleistocactus strausii, Cylindropuntia imbricata), all of which are equally undemanding plants. A good way to highlight agaves is to plant ground cover plants for dry soil at their base: evening primroses, Osteospermum, dwarf artemisias, Ceratostigma plumbaginoides, and Delosperma cooperi, whose foliage will hide the gap left by a dead plant. This agave can also be grown in a pot on a terrace, among a collection of cacti, by carefully choosing the sunniest spot. Remember to keep this beautiful plant away from high-traffic areas and young children!

Agave is also an edible plant, used in Mexico to make mescal, an alcoholic beverage obtained by fermenting its sugar-rich juice. It is also used in traditional medicine in Mexico, Brazil, and India, and has proven antifungal properties. Its inflorescences are highly attractive to many pollinating insects.