Gardening: Green Energy

Plants bring positivity to any environment. Houseplants will invigorate your senses during the darkest time of year – but go easy with the watering, says Flo Whitaker 

Plants constantly respond to stimulus around them, but, unlike us, they cannot shout in protest or run from a hostile environment. They take a while to indicate displeasure, with tell-tale signs often occurring around this time of year as they adjust to diminished light levels. 

The availability of light is the prime influence on houseplants, (they can also detect the difference between natural and artificial light). As a response to shortened day length, their active growth has slowed significantly now and many are simply ‘ticking over’. Most cacti and succulents, (excluding winter-flowering kalenchoe and schlumbergera, appropriately known as ‘Christmas cactus’) have now entereda semi-dormant phase and require minimal food/water. 

Houseplants that have spent summer outdoors can find the return to indoor living particularly stressful. Gentle leaf-shedding is part of the natural process, but a large quantity, particularly if lost in a sudden drop, may be an indication that all is not well, so be vigilant. Knowing the characteristics of your plants and honing your observational skills are the keys to good gardening.

Over-watering is the primary reason why houseplants perish in winter. During spring and summer, most plants are in full growth mode. They will often survive a short period of waterlogging as their clever vascular systems enables them to efficiently syphon excess water away from their roots and evaporate it through leaf pores. However, in winter, the vascular process is greatly diminished, so roots sit in permanently wet soil and begin to rot. 

The first signs of overwatering or underwatering look remarkably similar. Parched, underwatered leaves droop, while overwatered ones flop as excess moisture ruptures their leaf tissues. You can’t necessarily tell one from the other with a casual glance, so inspect the compost and, if possible, turn the plant out of its pot. 

Over-wet soil has a distinctive stagnant aroma and the pot will feel conspicuously heavy. Temporarily moving the plant to a warmer/sunnier spot will accelerate the drying-out process. Laying the plant on its side will hasten drainage, but if soil is wringing wet, re-potting into fresh compost may be required. In contrast, underwatered specimens feel super-light, with desiccated compost that has shrunk away from the pot sides.

Adding a drop or two of washing-up liquid to water will break its surface tension, making it easier to re-wet the soil. Small plants can be submerged entirely in a bucket of water for a couple of hours – then drained thoroughly. 

Common garden pests can be troublesome on houseplants. In an outdoor habitat, natural predators offer good pest control, but an indoor setting gives aphids and slugs a cosy, predator-free playground, enabling them to reproduce all year round. Pay particular attention to plants that have lived outside during summer – they can bring unwelcome stowaways indoors. 

Bedding geraniums, pelargoniums and citrus plants can be successfully overwintered indoors. They’ll stoically survive in a dry, cold, (minimum 100 C) frost-free conservatory or porch environment, but must have a brightly- lit spot, otherwise they’ll drop excessive amounts of foliage and may not recover in spring. As a space-saving measure, geraniums and pelargoniums can be cut back by half. This also greatly assists with air circulation, as their velvety leaves are prone to attracting damp and mould spores. 

Consider the position of your houseplants. Areas that are too sunny in summer may become good locations in winter. Conversely, a lightly-shaded summer spot could be too dark currently – and the plant that was happily trailing over a cold radiator in August will now be turning crispy! Review the situation and make a switch-around if necessary. If possible, move plants from windowsills at night. They suffer when pressed against chilly glass, while drawn curtains create a barrier that prevents warm air within the room reaching them. 

Although in a wintry slow-grow phase, plants still need to photosynthesise and can do this most efficiently if their foliage is clean. Regularly inspect and dust your houseplants using a gentle-bristled brush, or wipe leaves with a soft cloth moistened with cool water. Oh, and if you ‘temporarily’ evict a houseplant to make way for your Christmas tree, remember to put it back in January. A forgotten, dust-covered plant shoved into a dark corner is a miserable sight.