Winter Hardy Agaves & Yuccas

Germany's Jürgen Eisel chooses a selection of these exotic plants.
Jürgen Eisel, Schalltorstr. 19, 5455 Rengsdorf, Germany
Chamaerops No. 6, published online 23-10-2002

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Succulent supermarket: Spoilt for choice.

At the age of thirteen, the view of a few large Trachycarpus on a promenade near Saint Malo awakened in me a passion for collecting plants, which has remained to this day.

Meanwhile my garden houses a notable collection of subtropical succulents and shrubs, which draws attention not only from plant experts.

Beside different palms (Butia capitata, Butia yatay, Sabal minor, Trachycarpus fortunei, Trachycarpus wagnerianus) there are also Acacias, Eucalyptus, Laurus, Cistus, orchids and different bamboos planted in the garden. Another large portion is inhabited by succulents such as Agaves, Yuccas and 200 species of cacti. In this article, I will report on Yuccas and Agaves, other subtropical shrubs and succulents will be dealt with in a later one.

All plants, which have the capability of storing water in the tissues of their stems or leaves are defined as succulents. Succulents grow in arid regions where rainfall is low and limited to specific times. In many cases, these plants have to endure long periods of drought in their native habitats, which alternate with only short periods of rain.

Some desert inhabitants near the coast can also utilize nightly dew or mist as their water supply, besides the rain.

Through the ability of succulents to store water, they are perfectly adapted to their native stands and can survive the dryness without damage, but along with this goes a corresponding transformation or reduction of leaves and stems. To reduce evaporation during the dry periods to a minimum, many succulents have a thick cuticle, wax cover or tormentous hairs on their leaves, or rosette-like structures like Agaves for instance.

Agaves and Yuccas are generally known as house or tub plants. That there are many species that are winter-hardy under the climatic conditions of central Europe, if certain requirements are met, is only little known.

In their native habitat, many of these plants survive frost and cold in total dryness, whereas our early winters are often cold and moist and winter alternates many times between frost and thaw. That is why some succulents that are frost-hardy here, need protection from too much wetness, through drainage or a roof for instance.

For outdoor planting of all winter-hardy succulents, the selection of a location that will suit their requirements is a most important factor. Microclimate and soil quality play an essential role. One can proceed on the assumption that most succulents suitable for planting out prefer a sunny, warm location and are sensitive to too much moisture, especially in winter. With suitable drainage with gravel, etc. and maybe a rain shelter from October/November to March/ April, depending on the weather situation, the plants can be protected. Another positive influence on the microclimate can be obtained if the ground between the plants is covered with expanded clay granules, such as those used in hydroculture, or rocks and stones.

Some species suitable for planting in central and northern Europe are:

Agave megalacantha, Mexico. Although from Mexico, this species is fully, hardy. It grows loose rosettes with 20-25 leaves, 15-25cm in diameter. The leaves are broad (8-12cm), 18-20cm long and are oval, grey-green to blue-green in colour, with sharp brown thorns on their margins.

Agave parryi, Western North America. Compact growing, stem-less with leaves 20-30cm long and 6-10cm wide. The tip thorns are 2-2.5cms long. Hardy. Variety Couesii is very hardy.

Agave utahensis var. utahensis. Utah, USA. Bluish leaves 12-20cms long and 2-5cm wide in rosettes 20-30cms dia. Suckering. The varieties Eboruspina, Diskret, Kaibabensis and Nevadensis are not similar. They are very sensitive to moisture but very hardy (-20°C) if kept dry.

Agave lechugilla. Texas, USA. Sickle-shaped green leaves 20-35cms long and 2.5-3cms wide in rosettes 75cm in diameter. The leaf tips have brown thorns l.5-2cms long. Suckering. Hardy.

Agave toumeyana var. Bella. Arizona, USA. Dense, carpet-forming rosettes to 30cms in diameter. Leaves 1520cms long and 10- 2Ocms wide - light green with white colouring - with fine white threads on the margins. Hardy.

Agave schottii. Southern Arizona, USA. Leaves to 27cms in length and 5-8cms wide, margins with fine threads. Tip thorns 7-10mm. Tender.

I guess Yucca filamentosa, Y. flaccida, Y. glauca, Y. recurvifolia and Y. gloriosa are quite well known. These plants don't need rain cover here and survive our frequently wet winters without damage.

Agaves and Yuccas are the stars of every succulent collection and together with palms and other subtropical shrubs, they complete the exotic appearance of a 'Riviera garden'.

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