Cacti are often grown from seed in highly sheltered and controlled conditions and even in nature cactus seedlings are often associated with what are known as nurse plants.
However the rainfall patterns of most arid areas are either cycles with periods of rain and then dry periods, or they are sporadic and some years may occur more or less frequently.
For a tiny cactus seed to germinate and become a seedling is but one stage in a long journey for the organism.
Once the seedling has roots and grows towards the light, it is in a race against time.
The coming drought in a seedlings life poses one of the biggest challenges to its existence. If it cannot obtain the right size and mass it will not be able to withstand the approaching dry weather, which may also be quite hot as well. To prepare and survive the drought many cactus seedlings have a hidden strategy, they are often robust and fast growing plants.
Even in the company of protective nurse plants, which typically buffer and shelter the plants from the raw environment, the conditions found in nature are unlike those typically provided for young cactus seedlings in culture. While nurse plants often provide shade or filtered overhead light, they frequently also allow direct sun to reach the seedlings in the evening or morning as it comes in at an angle.
After germination cactus seedlings often need to grow as fast as possible to become as large as they can get to be able to withstand the coming dry and hot weather and they are equipped to handle very bright conditions so as to eat as much light as possible to assist their survival. While excessive heat will kill them, newly germinated cacti are more light tolerant and much faster growing than is often realized . They must also be fed or have nutrition available to them to do this and while cacti respond poorly to high fertilizer concentrations they are well adapted to handling constantly available low concentrations in culture that mirror the fertility of natural conditions. In many examples nurse plants fix nitrogen and gradually shed their leaves enriching and conditioning the soil near them over time.
Cacti including those commonly grown from seed also have their own special microbes, yeasts, bacteria and fungi that assist in their survival and are passed down from mother to seed as endophytes. They can be considered ecosystems not unlike lichen, but the algal component is in this case the cactus itself, which like all flowering plants is considered to have a algal ancestor. The recognition of individual specimens as entire communities of organisms has led to the term Holobiont being applied to them and indeed cacti can be considered such, as can the majority of organisms on this planet.
In nature cacti in niche conditions have nearly unlimited air exchange while in culture it is common to restrict air exchange and retain humidity, while also limiting light and in many cases applying fungicides and or antibiotic substances. This approach, while effective may be somewhat limiting in terms of the rates of growth and health of the seedlings. As mentioned above in order to survive in nature many cactus seedlings are vigorous and fast growers under natural conditions.
Different cacti will always grow at different rates and strategies that allow for neglecting plants for years because of extremely slow growth rates have a place in the culture of the plants. However it is also good for growers to be aware that other strategies that mimic ideal natural conditions may also be more effective and result in healthier, larger plants in considerably less time than some of the more well known methods are capable of providing.
The downside is that more attention is required typically to grow the plants more naturally and the rates of growth are so fast that it is easy for a grower to be overwhelmed with plant material rapidly. A single seed of various popular columnar cacti can often produce a kilogram sized plant or larger in a single season. A few thousand seeds can, in a short time, literally become a ton of plants.
Being able to sow and grow large numbers of cactus seedlings in a short time also allows for the sorting, screening and selection of very large numbers of plants in a relatively concentrated space, as that cacti can often be maintained in miniature or grown more slowly deliberately. When grown in more ideal conditions cactus seedlings often also display traits of distinction, such as monstrose, crested or variegated growth or other alterations and variations in the general growth pattern. Rather than growing small numbers of representatives of crosses, as is a common strategy employed by collectors, it is also possible to grow very large numbers of plants and select the most unique or unusual specimens and then give away, sell or even discard the rest. In fact both strategies are known to breeders. The first is called Single Seed Descent and it's where a grower or breeder randomly selects a seed or plant from a generation to grow and use in crossing. The second method, where large numbers of seedlings are screened and special specimens are selected to grow and use for crossing; is known as the Pedigree Method. Both are very useful methods for breeders but can also be useful to growers and collectors as well.
Ideally, for cactus collectors to use the Pedigree Method, even if they aren’t breeding the cacti they can select the more ideal specimens from among larger populations and methods that grow increased numbers of well developed plants can reduce the time and space required for this to be done.
As mentioned also in the
overview of hybrid introgression, in some cactus populations traits can be linked and tend to be inherited together. If a breeder or grower knows what they are or aren’t looking for and they know the inheritance patterns, they can use natural culture methods to isolate and obtain unique specimens that they would be, statistically speaking; otherwise unlikely to find.
Author
Topic: Nurse Plants and Natural Culture: Cactus Strategy (Read 1467 times)