As you know, Cactus plants can stand drought and high temperatures. Ideal for deserts, they can survive for long periods of drought. Large cactus plants that you see in desert pictures are anywhere from 50 years old and up.
From seed to germination, depending on the species type, can grow anywhere from 3 weeks to a year. This takes time and patience in learning how long each species takes to grow. It is not something you can teach, as it will depend on equipment you use, condition, and time of year you plant them. Factors that you must consider when planting your seeds are, various times it takes to germinate and growing seedlings indoor or outdoor will change the growing conditions depending if you can control the weather or not.
After you have achieved germination stage, keeping them alive in a 70 mm pot is a challenge. You are introducing them to light, warm air and less water. Things can change from better to worse, by having too much light as it can burn the seedlings easily. Mealy bugs and other diseases can affect them as well. Keeping an eye on them is so essential to their needs. Cactus plants grow in spring and summer periods, followed by a dormant period in the fall and winter. The age of the plant can be up to 3 years at this stage.
By the time, they reach 100 mm size pots, they are anywhere from 4 to 7 years old, and the growth of the plants have slowed down dramatically. At this stage, re-potting each year will help keep the roots healthy. Fertilizing every 3 months helps keeps their rich colour from fading. You will need to give them insecticide at least every 6 months, especially plants with less thorns. If you are thinking of starting a garden this size and up the plants will cope with the conditions of the weather, as long you give them time to adjust to the climate. Planting them in late winter will help and it is the best time to start a garden, as it is cool outside.
When planting them into the next size pot, make sure there is enough room left to grow. Especially larger plants, you will find they will break the plastic and clay pots because their root system is so strong. Choosing the right spot, is so important to their growth and well-being and they are getting heavy at this stage. When they are starting to reach the age of 15 years plus, they will need 200mm size pots and up, good for gardens and feature plants on verandas or stairs.
Cactus plants can live for many years all depending on their species. They can even outlive you.