How to grow a cactus - Encyclopedia

Introduction

Cacti grow in many parts of the world, especially South America and Africa. There are several different kinds of cacti accommodated by our planet. Cactus plants like to grow in places where little other plants like to grow since most cacti grow in arid regions, people often associate them with deserts. However, only a small part of cacti grow in extremely dry areas.

Cacti have always been popular plants, partly due to the enormous variety of cacti we can find and the little care they require to grow and live. This means that cacti are the ideal plant for any kind of gardener.

Because most cacti need very little care to enjoy a healthy environment, they are extremely easy to keep in and/or outdoors. Due to the great variety of cacti, it can be quite difficult to describe the ideal circumstances for each to grow. They each have their own preferences. However, there are many growing environments that apply entirely or partly to most cacti.

Pots

The size of the pot is very important for the cactus. If the pot is too small it can cause the roots to asphyxiate. The cactus will hardly grow, or growth will stop and eventually the cactus will die. If the pot is too big and it has too much soil it will hold too much water and this can eventually cause the roots to rot.

In general, you can say that the bulbous cacti (i.e. from the Lophophora family) are most comfortable in pots that are just slightly bigger than their roots. The tuberous cacti (i.e. from the Trichocereus family) normally need a bigger pot than the bulbous cacti.

The pots are normally clay/ceramic or plastic. The hobby growers normally choose pots made of clay. These pots allow the cacti to breathe better and the soil dries faster inside. Clay pots are more expensive than the plastic ones.

Make sure the pot has one or more holes in the bottom. Cacti prefer to soak up the water from below rather than from above.

Cactus soil

Good soil mixture can make a big difference for the health of your cactus. However, the choice of the soil mix largely depends on the climate conditions.

Normal pot soil is generally not suitable for most cacti, this soil has the capacity of keeping water for a long time. This is something that horrifies cacti. Garden centres offer special cacti soil. This soil will work just fine for most cacti. However, most hobby cultivators prefer to use mixtures that they have prepared themselves after many years of experience.

Ingredients which are often used in cacti soil mixtures:

• peat
• coconut fibre
• pot soil
• small gravel
• perlite
• pumice stone
• lime stone

Most mixtures are made of 20-25% organic material and the remainder is an inorganic material. It's very important that the mix is loose and light. If this is not the case, it will hold too much water, and this can cause the roots to rot. Cacti also need sufficient nutrients and trace elements. Eventually, the soil will be depleted of these nutrients. It is therefore recommended to add a little manure to the mixture once a year to keep a buffer.

Light

The right amount of light is the most difficult part of the maintenance of cacti. Especially if you live in a cold dark country you should make sure that now and then your cactus receives plentiful light. Cacti are naturally used to receiving lots of light. Most cacti can survive with less light, but this will slower their growth and they will never start flowering. During the summer, cacti normally receive more sun light than in the winter. Most cacti actually need just a few hours of full sun light. Don't forget to always place the (mature) cactus near the window. It is also possible to provide the cactus with artificial light. The fluorescent lamp is an option, as it provides plenty of light. The disadvantages are that these lamps give little warmth, and they have to be placed at a maximum distance of 10-30 cm above the cacti. Another alternative is the halogen lamp. This lamp gives off a lot more heat. HPS (High Pressure Sodium) lights are great, but energy usage is high.

Keep in mind that too much light can cause problems. Should the cactus receive too much light, the side exposed to the sun will lose colour, resulting in burn marks. This can cause permanent scars.

Temperature

It is well known that cacti enjoy the warmth. That is why they grow mostly in the warmest regions of the planet. But even the warmest countries often have cold nights. For that reason, many cacti can withstand colder temperatures. Some cacti are even able to endure frost for a short while, provided they receive plentiful heat and light during the daytime.

Indoors, cacti can generally be kept at room temperature. In the regions where cacti also survive outdoors, it may be better to keep them inside during the winter time.

Watering

The most common death cause for cacti is overwatering.

Our advice, therefore, would be:

Do not over-water your cactus!

Most cacti die because people give them too much water. Most people find it difficult to know when their cactus is in need of water. So the best thing to do is let the soil dry out completely before watering again. A humidity meter can be very useful in this case. When in doubt, it is best not to water your cactus yet.

In summer cacti need more water then in the winter.

General guidelines:

Summer: water your cactus once a week

Winter: water your cactus once to 2 or 3 times during the entire winter period

However, these amounts can vary tremendously depending on the cactus and environment!

Watering from the bottom is preferred. Cacti like to absorb water from bellow where their roots are. Therefore the pot must have one or more holes in the bottom and a dish/saucer underneath it. When you fill the dish with water, the soil will absorb the water from bottom to top, easily reaching the roots of the cactus. Get rid of any water that has not been absorbed within two minutes. Larger cactus plants might take a minute or two extra to soak up the water.

Transplanting

Cacti, and especially their roots, don't like being repotted. However, some cacti grow really fast. If they live in a too-small pot, the cactus can become root bound. The cactus will stop growing and eventually dies. That's why they need to be transplanted once in a while to a bigger pot to keep on growing.

Some care is needed when repotting a cactus. It is not just the cactus that can be damaged. The prickly needles are hard not to notice (ouch!) Therefore, always wear thick gloves or a folded cloth to protect your hands when handling a cactus. Be careful!

The best time to transplant cacti is right after the winter period.

Diseases

Most cacti are vulnerable to the same sicknesses and plagues as the normal home and garden plants. Therefore it's really important to check your cacti regularly for whatever vermin may appear. Also here prevention is better than cure. So make sure you create the right environment where the cactus can grow at its best, but germs and insects stand no chance.

Fungicides and pesticides can quickly eradicate nasty bugs and pests. However, be aware of overdosing of such fungicides and pesticides. Often the cactus will die because of these products. Always carefully follow the instructions printed on the package, always use animal and environment-friendly products.

The most common diseases are:

Rot

• infestation of roots and bottom of stem by fungi and bacteria
• recognizable by a dark colouring
• cactus feels soft/mushy
• it spreads to the upper part
• problem: soil mixture not permeable enough and/or too much watering

solution: save what can be saved. = make cuttings from the healthy parts

Frost damage

• recognizable by parts of the stem getting brown/black and chubby after de-icing
• can be prevented by enough warmth and ventilation

The most common plagues are:

Mealy bug

• the most common plague amongst cacti
• normally white coloured
• small, oval insects
• produces a white waxy substance
• it sits around the roots, stems, leafs and/or young plant sprigs
• it is a slow-moving insect
• solution: special insecticide for mealy bug
• when you notice that a cactus is infected, immediately separate it from the others

Aphids (plant lice)

• small round/convex insects
• normally green coloured
• normally appears in great amounts
• can cause black fungus
• solution: insecticide, gauze-flies, ladybugs

Scale insect

• different types varying from 1 mm to 1 cm
• different colours varying from white to brown
• quite uncommon on cacti, and is normally brought in by new plants in the collection
• remove the insects with your hand or a brush, most pesticides don't work well enough to get rid of adult scale insects

Trips

• winged insects smaller than half a millimetre
• yellow brownish with the shape of a rice grain
• move fast forward on the plant
• withdraw food from the plant spreading a bronze to silver colouring on it
• show up for no reason and often disappear again by themselves
• easy to fight of with the appropriate products

Multiplying your cacti

Growing from seeds

An easy way to set your first steps in the cultivation of cacti is by growing from seeds. Most cacti seeds germinate quite easily and do not require too much care or a very specific growing environment.

The first step is choosing the soil mixture. There are several different recipes for a proper soil mixture.

A proven and widely used soil mixture consists of:

• 1/3 pot soil
• 1/3 peat
• 1/3 small gravel (1-3 mm)

As upper layer, use sand or gravel (1/2 - 1 cm.).

One of the risks when growing from seeds is the huge amount of bacteria contained in the soil mixture. Especially in the early growing phase, the seeds are very vulnerable to various diseases and plagues. It is therefore important that the soil mixture and the top layer of sand or small gravel are sterilized before the seeds are planted. This sterilization can be done with a pressure-cooker or a microwave. It is preferable to use the pressure-cooker because it delivers better results.

Pressure-cooker: 60 minutes on 15 psi

Microwave: 8 - 10 minutes maximum watt

When the soil mixture has cooled down and the pots (with holes underneath) are filled, cover the upper part with a thin layer of sand or gravel (also previously cooled down). The seeds may now be planted. Do not press the seeds any further in the soil. These very small seeds will not germinate if they are placed too deep in the soil. Spreading them carefully is more than enough. Finally, give the seeds and the soil a good spray with water. The seeds will then sink down a bit all by themselves. It is advisable to use a (light) fungicide at this time to prevent bacterial contamination. Place the pot in a bucket with water for about 5 minutes, so the soil can also absorb the water through the bottom holes.

Now it is time to let the seeds germinate. Keep the pots in an environment that meets the followings requirements:

• Warmth. Keep the pot with seeds in a warm spot with a (constant) temperature between 20 and 30 °C
• Light. The seeds need some light to germinate. However be sure to keep them somewhere away from direct sunlight. Seeds and small cacti are very sensitive to (bright) sunlight
• Humidity. Germinating seeds love a high level of humidity in the air. The ideal percentage of humidity is between the 60 and 90%. To easily reach these levels, keep the seeds in the smallest possible growing space. This means that in the early phases of germination the seeds should be kept in a closed pot or bag.

After 3 to 10 days the seeds should start germinating. From this point on most of the work will be processed by itself. However, make sure the growing environment constantly meets the optimal conditions, to assure a good start to the newborns. After 2 - 3 months, punch a few holes in the bag every two weeks so that the small cacti can slowly get accustomed to the dry (or less humid) air.

After 6 months the cacti are already much bigger and stronger and can be removed from the closed pot or bag.

Cuttings

Growing from a cutting is done by simply cutting off a piece from a cactus and placing it back into the soil. However, wait two to three weeks before replanting. This gives the cutting time to heal the wound created when it was cut off.

The best time for making a cutting is the beginning of the growing season. If you cut a part from the cactus, always use a sharp and sterilized knife. If you don't sterilize the knife the cutting can suffer from infections.

Afterwards, let the cutting dry well before you place it again in the soil to grow. This drying period can vary per cactus from a few days to a few weeks. To let the cutting dry really well it is best to keep it in a warm spot with some air circulation.

A lot of cacti from which a cut was extracted will develop new shoots where the cutting was made. After a while, you can also cut these new shoots to use as cuttings.