Cacti – Exotic plants for the home and garden

The cactus family is vast, with around 1,700 different species, mostly native to the American continent. Just as diverse as the number of species is their appearance: Alongside dwarf varieties with only a few centimetres in diameter, there are giant cacti reaching up to 15 metres tall, and a wealth of attractive growth forms. Some grow in columnar, cylindrical, or spherical shapes, while others have a disc-like form. Some cacti have ribbed stems, others are segmented or wart-like. By the way, cacti don't have ‘spines’ – what we commonly call spines are actually thorns. There are also cacti with bristles or hair.

In addition to so-called leaf cacti, such as the Christmas cactus or the sawtooth cactus, there are also farmer's cacti and candelabra cacti, pachypodiums like the Madagascar palm, living stones, and many other interesting species suitable for cultivation indoors. Despite all this diversity, cacti have one thing in common: they can store water and, with a few exceptions, are classified as succulent plants.

The various species of cacti that thrive as houseplants have somewhat different requirements. Generally, you can't go wrong with care if you place the plants in a bright and sunny spot. Windows facing east, west, or south is optimal. However, be careful: direct sunlight right against the window is not ideal. Most cacti cannot tolerate it for long, as they can get sunburned. It’s better to have a spot on a shelf near the window: 10 cool DIY ideas for where your cactus can find a stylish place. You can also create beautiful plant stands or flowerpots for your cacti from tree trunks.

In the natural habitats of cacti, it is often very dry, making them ideal for living rooms and offices. In bathrooms or other humid areas, succulents are less likely to thrive. What cacti cannot tolerate is moisture. Therefore, pots must have drainage holes to allow excess water to escape. If the cacti are in decorative outer pots, you often can't see if water has accumulated. Regular checks are therefore important. If there is water in the outer pot, pour it out to prevent waterlogging. Otherwise, the roots will rot, and the plant will eventually die.

Very important for cacti: It’s better to water too little than too much. Cacti don’t need much water; as succulents, they can store water and can go without it for a while. Especially in winter, watering is often a no-go.

Pay attention to the growth, drying, and resting periods of your cacti. Here, we explain when and what to focus on.

The winter dormancy of most cacti ends in early March. Now you can place them in a warmer spot and resume watering. To avoid shock, the temperature should be gradually increased, allowing the plants to acclimatise to their new environment slowly. Between March and September, cacti should be watered regularly, but only when the soil is dry. You should water thoroughly so that the root ball absorbs water, and then pour out any excess water. Alternatively, the root ball can be placed in a container of water. Small air bubbles will form as the root ball absorbs the water. Once no more bubbles are visible, you can remove the cactus from the water and return the pot to its original place. Fine misting of water over your cactus from time to time is beneficial and helps to remove dust deposits.

During the main growing season between April and August, it is beneficial to provide your cacti with nutrients about once a month. However, they are not properly nourished with regular houseplant fertiliser. Cacti grow slowly and they require much less nitrogen than other plants. Special cactus fertilisers are tailored to the needs of these plants.

Many cacti, such as the golden ball cactus, also known as the ‘mother-in-law's seat,’ are usually cultivated indoors but can spend the summer outside. In mid-May, when no late frosts are expected, you can move them outdoors. Initially, a shady spot is best; it shouldn’t be too hot. Once your cactus has acclimatised to the outdoor conditions, you can place the pot in a bright and sunny location, but protected from heavy rain and wind.

In September, it’s time to find a nice spot indoors. From late summer onwards, gradually reduce watering so that your cacti can acclimatise to their winter dormancy.

In the cold season, many cacti enter a period of winter dormancy and growth rest. Some species, like the Christmas cactus, already require a rest starting in August/September, while most others need 3 to 4 months of dormancy beginning in October/November. For good development in the following year, temperatures during the dormancy period should be between 10 to 15 °C. Fertilisation is not necessary. When the root ball is dry, place your cacti in a cool location. At lower temperatures, their light requirements also decrease. A windowsill is sufficient at around 10 °C.

Snake cacti and some other species can tolerate warm spots year-round. If you don't have a cool wintering option, these plants are ideal for your home. It’s best to consult a specialist retailer for more information.

The optimal time for repotting is from early March to mid-May. Cacti are typically repotted every two to five years, or when the pot has become too small. It’s particularly urgent when the roots are already growing out of the drainage holes. The new pot doesn’t need to be much larger; an increase of 1 to 2 cm in diameter is usually sufficient. Many plants are thoroughly watered before repotting and then given a generous watering afterwards. However, cacti are different. They should only be placed in a new pot when the soil is dry. After that, let them rest for a week before watering. This allows the roots to acclimatise to the new soil; otherwise, they may rot.
 

Repotting very thorny varieties is not that easy. In addition to special gloves and cactus tongs, two polystyrene sheets, cut to the size of the cactus, are also very helpful, acting as a buffer between your hands and the thorns.

Cacti are hardy and low-maintenance, no doubt about it. However, only a few will flower without your attention. The most important factor is the dormant period, during which the plants form their buds. If they are watered, kept too warm, or fertilised during this time, no flowers will appear. If you’ve done everything correctly and still don’t see flowers, it could be due to the age or size of the cactus. Some cacti flower after two years, others can be after ten years, and some need to grow a bit before flowering. In that case, a little patience is needed.

There are exceptions: For the Christmas cactus to develop its first flowers in November, it needs to be placed in its resting spot as early as September. In November, it can be watered again and kept in a bright, warm location.

Cacti don’t just thrive indoors; there are also species like the hardy opuntia, also known as prickly pear or bunny ear cacti, and cylindropuntia varieties that you can cultivate outdoors in a suitable location. Their natural habitats aren't limited to deserts and steppes – cacti also grow in high-altitude regions, making some species well-suited to withstand freezing temperatures in our climate. They can be placed in pots on a balcony, terrace, or in the garden, either individually in rock gardens or as part of a full cactus bed with various species.

These exotic plants thrive in a spot with plenty of light and several hours of sunshine each day. In areas where other plants may struggle due to dryness and heat, cacti are perfectly suited. A location protected from the wind and having proper drainage are also important, as waterlogging is harmful whether in pots or in the ground. For the top layer of soil, it's recommended to apply a 3 to 5 cm layer of lava, gravel, or crushed granite between the planted cacti. This mineral material warms up quickly and allows for good air circulation.

A covering made of brushwood will help your cacti get through the winter, and a temporary roof to protect them from excessive moisture is also beneficial for these exotic plants. You can also build them a mini greenhouse or use a plant cover shaped like a tipi for added protection.

If you want to know more about when certain gardening tasks need to be done, you can find that information in our garden calendar, which provides the right timing for all important activities.