The spikes of life
As if their armour isn’t enough cactus also produce striking flowers
WE USUALLY admire cacti for their interesting shapes and sometimes vicious spikes. But in spring, many cacti also have really pretty flowers. Each flower usually lasts a few days, closing in the evening and opening again in the morning. Plants can produce dozens of flowers, so the floral show can last for several weeks. In the nursery, we often see native bees visiting the flowers. Cacti have adapted over the millennia to survive in the harshest of environments. Most have spines instead of leaves because the smaller surface area greatly reduces moisture loss through evaporation. The spines also protect the cactus from predators such as birds.
Most cacti are columnar or globular (spherical), producing a low surface area-to-volume ratio, thus reducing water loss, as well as minimising the heating effects of sunlight.
The ribbed or fluted stems of many cacti allow the stem to shrink during periods of drought and then swell as it fills with water when it becomes available. There are some cacti that look like little mounds of pebbles, and others that have spines so long and sharp they are positively scary. Some of the spines have hooked tips, and some are so fine that they are fuzzy rather than spiky. They are arranged in perfect geometric patterns over the cactus – quite mesmerising when viewed in close-up.
Cacti can be small, only a centimetre or two in height, to large at more than 15 metres tall. They don’t need a lot of care so they are perfect for the time-poor gardener.
A sunny position is best, even a sunny windowsill inside is okay. Cacti will do best if they are in a position where they receive good morning sun but are protected from the worst of the midday heat.
A cactus has a shallow, spreading root system, allowing the plants to capture as much of that scarce desert rain as possible.
These adaptations allow certain cacti to survive three years without water so make sure you water these plants sparingly. A cactus that is overwatered is much harder to save than one that is underwatered.
Cacti and their cousins, the succulents, work well as potted plants, and can co-exist happily together in the same planter. Because of their shallow, spreading root system, a wide shallow bowl is more suitable than a tall narrow pot. Make sure you use a potting mix specially formulated for cactus and succulents.
When handling spiky plants, protect yourself by wrapping the top in newspaper or bubblewrap and wearing gloves and long sleeves. Use a small paintbrush to remove debris that may be trapped between the spikes.
Feed them a couple of times a year with a slow release fertiliser, or use a liquid every few weeks.
CACTUS FLOWERS ARE POLLINATED BY INSECTS, BIRDS AND BATS. NONE ARE KNOWN TO BE WIND-POLLINATED