Why I have fallen for the houseplant

As the days slide into darkness, let’s enjoy indoor plants, says Monty Don and the houseleek tree is the most dramatic

NOVEMBER is one of my favourite months.The clocks have gone back and the days are sliding inexorably into darkness until the New Year starts to tilt things back up into the light.

It is the time to enjoy some of those plants that do not grow outside braving the weather, but which need the warmth and protection of our houses, conservatories or greenhouses.

I never used to be much of a houseplant fan until I visited the desert in Mexico and realised the incredible beauty of cacti and other succulents. Since then I have accumulated a modest array – a collection would be too grandiose a description – that I enjoy most at this time of year when so much else is fading into a soggy demise. It is not so much their flowering that astonishes me – although that can be truly extraordinary – but the sculptural shapes they cast; clean and clear and dry in a season when all around me everything is collapsing.

Perhaps the most dramatic, if only because it can easily become quite large, is Aeoniu marboreum or the‘ house tree ’. This is a sub shrub( or dwarf shrub) that can reach 1.5m (5ft) in its original Canaries and Madeira habitats.

They are members of the Crassulaceae family, which includes another favourite of mine, echeveria, which is also easy to grow as a houseplant that can happily spend its summers outside.

Aeoniums have rosettes of ‘flowers’ (which are in fact leaves) on long wrinkled stems and will produce panicles of small, star-shaped flowers although these are far rarer on home-grown plants. I have A. arboreum ‘Zwartkop’, with deep-purple leaves, and ‘Voodoo’, whose leaves range from a light green tinged with burgundy to a rich bronze.

Like most aeoniums these are both monocarpic, which means that if they do flower, they will die. So enjoy the leaves!

Aeoniums are often used as tender bedding although mine spend most of their lives in a greenhouse.

In winter it is important to let them become completely dry although they can be quite cool and do not mind some shade.

If the very dark leaves start to turn green or the lower ones fall off don’t be alarmed – they will regain their dark beauty in spring.

A very leggy plant can be rejuvenated by cutting the tallest rosette off with secateurs so it has just a couple of inches of stem. Let this dry for a few days then stick it in potting compost mixed with its own volume of grit – it is important that it is very gritty – and it will re-root and create a new plant.

The parent plant will grow new shoots from below the wound.

Don’t be alarmed if the roots appear ridiculously insubstantial when you repot it, All aeoniums have very meagre root systems as they use leaves and stems to store water rather than roots.

Despite this they will need a weekly water during their growing season and then to be kept almost completely dry throughout winter. All succulents have evolved to cope with extreme water shortage by preserving moisture within their cellular structure that they can draw upon when there is no other supply. Many also keep the stomata in their leaves closed during the day to preserve moisture and only open at night to transpire.

This tendency means that many succulents are very well adapted to extremes of both cold and heat and indeed thrive when there is a noticeable difference between day- and nighttime temperatures. Hence they are a rare example of a plant that enjoys a south-facing windowsill or greenhouse that can become really hot during the day then dramatically cool at night.