What you need to know about a cactus
Name: cactus (cacti in the plural). Various genus and species.
Plant type: succulent, evergreen perennial
Height: from less than 10cm to over 10m. In home gardens, usually less than 50cm.
Foliage: most have no true leaves.
Climate: arid, semi-arid but adaptable to most zones.
Position: generally full sun.
Flowering: varies with species.
Appearance and characteristics of a cactus
The cactus is probably one of the most misunderstood plants. Often seen as a spiky thing that thrives on neglect, the cactus can in fact make an incredible landscape or potted plant.
Although the majority of cactus plants don’t appear to have leaves, they actually do, but we call them spines—these are actually heavily modified leaves. These spines are the difference between a cactus and a succulent. A succulent that has thorns or spines on its leaf ends or margins is not a cactus.
Cacti respond very actively to their environment. Many have a short growing season that is synchronised with the ideal growing conditions. A cactus tends to be shallow rooted—this allows it to quickly take up any moisture in the soil from rain or dew. It can have rapid growth surges, or even burst into flower, after heavy rains.
The body of a cactus is technically its stem or trunk. Often green, grey or bluish in colour, it photosynthesises with this.
The appearance of a cactus can vary enormously, from globe shaped to column form to tree-like branched forms. Cactus flowers are simply stunning. They are often very short lived, but their colours include white, yellow, red, magenta and just about every other colour blend you can imagine. Most will not flower with regularity. They may flower like clockwork, or in response to heavy rain after a dry period, or they may only flower every few years, seemingly at random.
Uses for a cactus
A cactus can be used in many ways, such as:
• A feature plant in a hot, sunny, dry spot.
• A bold statement plant, using its form to architectural advantage.
• In a rockery.
• In garden areas where regular maintenance may be difficult.
• In pots and tubs.
How to plant and grow a cactus
Your cactus will likely come with detailed care instructions on the label. Keep hold of the information for later reference. Your cactus will thrive in full sun positions. Most types must have very open, sandy free-draining soil—putting a cactus into regular garden soil or potting mix will kill it very quickly. You may need to create an elevated bed or rockery filled with this type of soil. If planting your cactus in a pot, use a specialised cactus potting mix.
During peak growth times and the warmer months, water your cactus regularly, but allow it to dry out between waterings. In winter, when the cactus is dormant, only water very lightly when dry.
Your cactus does not need to be feed, however an annual application of a controlled-release fertiliser at half rates will give you healthier plants and increase the likelihood of flowering.
How to plant cactus
Do not try to push the roots deep into the planting hole or pot. A cactus is shallow rooted.
To make planting, potting or re-potting a cactus a less painful experience, wrap newspaper six or eight layers thick around the part of the plant you plan to handle and secure it with sticky tape. Remove once planted.
Caring for a cactus
The most common cause of cactus death in the home garden will be overwatering. Follow the general tips above and any specific instructions on the label.
Growing cactus from seeds and cuttings
There is a lot of variation as to which method will be most appropriate, depending on your cactus. As a general guide:
• If seeds are available these will germinate readily if sown when fresh in moist, not wet, propagating mix and kept warm.
• Some species throw out “pup” plants or offsets from around the base. As they mature, these can often be removed and planted out into the garden or individual pots.
• Many types of cactus will grow readily from cuttings. Allow the cutting to dry completely before positioning it in a pot or tray of propagating mix.
If you like this then try
Indoor plants: find the perfect potted plants to grow indoors.
Agave: this succulent is the perfect companion for a cactus.
Dragon tree: a spectacular larger succulent for the garden or pots.
Start planting today
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Asbestos, lead-based paints and copper chromium arsenic (CCA) treated timber are health hazards you need to look out for when renovating older homes. These substances can easily be disturbed when renovating and exposure to them can cause a range of life-threatening diseases and conditions including cancer. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page.
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