Plant Spotlight – Agave americana

Cacti and succulents play an important role at Winterbourne. Since 2008 our amazing Arid House has been used to display hundreds of species of desert dwelling plants. We even use them outdoors in summer as part of the many different seasonal displays we create around the Arid House and the Terrace.

However, of them all there is always one species in particular that attracts the most attention and at Winterbourne it is  Agave americana, commonly known as the ‘century plant’ as they can take many decades to flower. This giant of the arid landscape makes for an impressive specimen, growing huge fleshy leaves up to 1 metre in length, that unfold one-by-one from a central cone-shaped point.

Although tipped by vicious spikes, Agave are really classified as succulents rather than cacti, which not only have spikes and spines to keep hungry predators at bay, but areoles which are modified leaves from where the clusters of spikes are grown. Only true cacti have areoles, and all other fleshy, spiky plants are deemed to be succulents instead.

A native of southern USA and Mexico, Agave americana has beautiful blue-grey foliage and sprays of yellow flowers held aloft atop a huge flowering spike that can be up to 8 metres tall! Our oldest specimen in the Arid House is now probably large enough to flower, and when it eventually does, we will have to remove the glass panels above its head so it has enough room to grow.

Several years ago, another impressive Agave in our back-up collection behind the scenes,  Agave victoriae-reginae, or the ‘Queen Victoria century’ plant,  surprised us and started to flower. There was a lot of head scratching as we considered where we could display the rapidly growing plant without hindering its skyward ascent. Eventually we resolved to put it in the stairwell on the ground-floor of the House, where it could extend upwards spanning two floors and be seen up close by visitors when climbing the stairs. The move was a success and the huge flower spike grew to 3.5 metres tall in just 5 weeks, although it did need to be turned every day, to stop it leaning dramatically towards the light of a nearby window.

Sadly Agaves are monocarpic, meaning that they die once they have flowered. This is not an uncommon phenomenon in the plant world and makes the wait for long anticipated flowers a rather bitter-sweet affair. Happily they usually produce lots of baby offsets long before they die, which are easy to detach from the mother plant and if potted on will create a succession of new plants to be used as replacements at a later date.

Agave americana ‘Variegata’

There are lots of other species of Agave which merit inclusion in the garden. A. americana ‘Variegata’ is commonly grown, having brilliant yellow and green variegated foliage. A. americana ‘Mediopicta’ is also grown for its variegation, but this time steely-blue and white. We have paired some nice specimens of A. americana ‘Mediopicta’ in pots on the steps at the end of the Pergola this year, alongside other blue-leaved succulents such as Echeveria and Sansevieria.

Agave americana ‘Mediopicta Alba’ with Echeveria and Sansevieria

Agave tequilana, or the blue agave, has long been cultivated in Mexico for its use in the production of Tequila. First, when the plants are about 7 years old, their succulent hearts are removed. These are called piñas. The hefty piñas are then stripped of leaves and roasted in a hot oven before being crushed to release a sugary liquid which can then be fermented and converted to alcohol. Traditionally the finished product is flavoured with a mezcal worm, an insect larva with a very pungent taste.

Agave are tolerant of relatively low temperatures but should never be allowed to freeze. Therefore specimens grown outdoors will either have to be brought indoors into a glasshouse for winter, or afforded some other form of protection in-situ, such as a cloche. They should be grown in good quality, free draining cactus compost, watered twice-weekly through the summer, and kept near dry in winter. A balanced feed every 2 weeks during the growing season will keep your plants growing strong.

Agave make good house plants if placed in a sunny spot but most species simply grow too large (and too spiky!) to be practical. However, Agave parviflora is a perfect option, growing to only about 20 centimetres tall. It has familiar lanceolate, sharp-tipped leaves, but the foliage is also decorated at its margins with wisps of bright-white thread, like an old man’s beard. Worthy of adding to any indoor plant collection, Agave parviflora has even been bestowed the coveted RHS Award of Garden Merit.