What important factors affect the survival of succulent cuttings?
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Text and images: Hello, succulent fans
What kind of material should be chosen for cuttings to have a higher survival rate? Why is it said that succulents that are left to dry for a while are more likely to grow roots? Is it good for succulents to receive light during cutting? Why can succulent leaves placed on a stone slab all grow small pups and roots? Why do leaves placed on moist soil surface not only fail to grow roots but instead rot? What temperature is good for cuttings, and is it good to take cuttings in winter? After reading this article by Fenghua, the questions above will all be no problem at all. Watch it together with the previous article on succulent cutting methods, and succulent cuttings will never stump you again.
Important factors affecting the survival of succulent cuttings: the material basis for rooting in the cutting material
1. Rooting promoters
The substance that plays an important role in rooting is "rooting hormone," which is what we usually call growth hormone. It can transform ordinary cells into root primordium cells, and it can accelerate cell division, promote rooting, and inhibit the growth of lateral buds. During cutting, auxin must be transported to the base of the cutting, making the base the most active part, and only then will rooting occur.
Where is auxin?
Auxin is mostly concentrated in the most vigorously growing parts of a plant, such as the apical bud, cambium, coleoptile, meristem at the root tip, ovary after fertilization, young seeds, and so on, while there is very little in tissues and organs that are tending to age. This is also why cuttings should not use perennial plants and woody stems with aged structure for propagation.
Solutions:
A. As the mother plant ages, its rooting ability for cuttings declines. This is because the rooting promoters contained in its body become fewer and fewer, cells age, the functions of various organs decline, metabolism weakens, tissue vitality and adaptability also decrease, and regeneration ability is weak. Therefore, try to choose young plants that are one or two years old.
B. After cutting off the part to be used for propagation, leave it to dry for as long as possible. One purpose is to let the wound heal, and another very important purpose is to let the plant properly shrink. After the plant shrinks, the water in its body will transpire away, but the concentration of auxin will increase, which is more conducive to propagation and survival. The reason is simple: if you mix 10 g of milk powder with 100 ml of water versus 200 ml of water, which one has a higher concentration?
C. For varieties that themselves have low auxin content, you can artificially supplement rooting powder such as indoleacetic acid, indolebutyric acid, naphthaleneacetamide, and naphthaleneacetic acid. ("Rooting powder" is sold on the market.) You can dissolve the rooting powder in water and soak the cuttings to carry this out. In this way, the medicine can be absorbed by the plant into its body, which is more effective than directly smearing rooting powder. But you must not blindly rely on using it, because too high a concentration will instead inhibit rooting.
2. Nutrients needed for rooting
A. Carbohydrates
Carbohydrates are nutrients essential for the cutting and rooting process. From cutting to rooting, the cutting must rely entirely on the carbohydrates stored in itself to maintain complex physiological changes and activities. Carbohydrates are an important energy source in the cutting rooting process. Therefore, if the cutting plant is in good nutritional condition, healthy and intact, with no surface wounds and no pest or disease damage, this is beneficial for rooting. So cuttings should be taken as much as possible when the plant is growing vigorously.
B. Nitrogen compounds
When root primordium cells divide, they need nitrogen to synthesize nucleic acids and proteins. If the cutting is extremely deficient in nitrogen at the time of cutting, the rate of root formation will be weakened. At this time, a small amount of foliar nitrogen topdressing should be applied. You can spray a low-concentration nitrogen-containing liquid fertilizer on the leaf surface, and it is better to use less rather than more. This can help rooting. However, under normal circumstances, the cutting itself contains sufficient nitrogen, and after cutting it is not suitable to carry out foliar topdressing, so as to avoid causing the cutting to rot.
3. Rooting inhibitors
Growth inhibitors and auxin are an old pair of rivals. During plant growth, their struggle and confrontation are everywhere, just like a tug-of-war. If auxin wins the tug-of-war, the plant will grow, such as sprouting and rooting. If the inhibitor wins the tug-of-war, the plant will show phenomena such as dormancy, leaf drop, terminal bud formation, and aging. However, growth inhibitors are also indispensable substances in the growth cycle. They play an important role in controlling growth and ensuring continued survival in unfavorable environments. The two basically exist together, and it just depends on who can suppress whom. Both are substances on which plants depend for survival!
How are growth inhibitors produced?
The production and operation of plant growth inhibitors are related to the intensity of sunlight and the photoperiod. The changes between day and night cause plant growth to form cyclical changes. In sunlight, plants generate growth inhibitors, so plant growth is slower during the day. Also, because the products of photosynthesis are accumulating during the day waiting until night to be distributed, under normal circumstances, plants grow much faster at night than during the day.
Although all things grow relying on the sun, in fact they store the sun's energy to grow at night. Therefore, at night in rural crop fields, you can often hear the sound of jointing, and sometimes in the morning you will find that bamboo and weeds have shot up a big stretch. This is also why in cloudy and rainy weather you will find that new shoots of tree branches grow especially fast, and it is also one of the reasons why plants become tall and leggy in dimly lit locations.
The leggy growth of new branches is also due to the lack of growth inhibitors caused by low light levels (artificial growth inhibitors such as "chlormequat"). This is also why, in crop production applications, cuttings from etiolated branches are more likely to root, because shading causes the plant to produce only very few growth inhibitors.
And the base of the cutting, inserted and buried in a dark environment substrate, will also cause growth inhibitors to gradually disappear, so the rooting position of the cutting is favorable for rooting in a dark environment.
Therefore, plants cannot receive light 24 hours a day either, as this will produce a large amount of growth inhibitors and lead to death. Some impatient flower lovers want to give plants more light, so they also provide supplemental light at night. This is the wrong approach. You still have to follow natural laws!
External environment affecting the survival of succulent cuttings
1. A good cutting substrate
The structure of the cutting substrate must have good physical properties. It should not only have good drainage and aeration, but also have the function of retaining a certain amount of water and air. For example: vermiculite, perlite, rice husk charcoal, peat soil, sawdust, furnace ash, and so on, which can be used in combination with one another. But they must all undergo sufficient disinfection treatment. Most of these substances have the characteristics of good heat preservation, water retention, fertilizer retention, and aeration, and they can all be used for cuttings in winter and in the relatively cold early spring. Because after rooting the plant needs to absorb nutrients to promptly supplement the substances needed for growth, the lower part of the substrate should be laid with planting material containing humus nutrients, so that the root system can penetrate and absorb nutrients. At the bottom, larger-particle planting material should be used to lay a drainage layer.
2. Maintain air humidity
Leaf transpiration will cause the cutting to lose water and die. To maintain the vitality of the cutting, the water vapor in the air around the leaves must be equal to the water vapor pressure between the cells in the leaves, so that activities such as cell division and photosynthesis in the cutting can proceed normally. Be sure to prevent the air humidity from dropping rapidly after cutting. The relative air humidity must be at least no lower than 70%. Especially in the period before the cutting roots, the relative air humidity is best kept at 90%. This is the primary condition for ensuring successful cutting!
Misconception: The 70%-90% relative humidity condition for cuttings refers to relative air humidity, not the relative humidity of the cutting substrate and soil. Too high relative humidity in the cutting substrate will only quickly lead to rot and cutting failure, because excessive substrate humidity will cause a large amount of bacterial reproduction. At this time, adventitious roots have not yet formed and do not need to absorb water. Therefore, high substrate humidity has no practical significance for the cutting and may cause suffocation and rot disease.
In fact, as long as the relative air humidity is sufficient, the cutting can even root in the air without substrate. You may have had this experience: in a greenhouse, branches that were cut with scissors and waiting to be used for cuttings have already sprouted roots. That is very likely because the owner cut them off and forgot them in a corner, and after one or two weeks they rooted in the air... because the air humidity in the greenhouse is absolutely very high!
In addition to spraying water mist, methods to increase air humidity can also include enclosed cultivation, but it must be opened every day for ventilation. This is because the plant needs to breathe and exchange air. Seedling box sets are sold on the market, divided into a box lid, a seedling tray, and a tray base. Using one at home yourself is quite convenient!
3. Provide appropriate light
The light level for cuttings actually needs to be maintained within a range of neither too much nor too little to be most suitable. Too much inhibits adventitious root growth, while too little leads to insufficient nutrient supply. This is because light is the energy source for plant photosynthesis. Generally speaking, with sufficient light and vigorous photosynthesis, more carbohydrates are formed, more nutrients accumulate in the cutting, and enough nutritional supply can be provided for rooting. Generally speaking, after cutting, just place it in a cool location with scattered light. Do not use direct sunlight, and do not use complete darkness. Direct sunlight will rapidly raise leaf temperature, causing strong transpiration, and the cutting will be dehydrated or sunburned.
4. Suitable rooting temperature
Temperature affects the cutting's cell division, photosynthesis, respiration, transpiration, and other physiological activities, thereby affecting the cutting's regeneration process. Different varieties have their own suitable temperature ranges. Within the most suitable range, rooting is rapid, while above or below this range, not only can rooting fail to occur, but it can also lead to death. Therefore, before carrying out cuttings, it is necessary to understand the suitable temperature range for this variety.
Cutting rooting temperature ladder table:
Generally speaking, for succulent cuttings:
When the substrate temperature is in the range of 8-10°C, a small amount of callus tissue forms.
When the substrate temperature is in the range of 10-15°C, callus tissue formation accelerates and adventitious roots begin to sprout.
When the substrate temperature is in the range of 15-25°C, the rooting speed rapidly accelerates as the temperature rises.
When the substrate temperature is around 25°C, it is the optimal temperature for cutting rooting, but it is easily affected by rot fungi.
When the substrate temperature is higher than 28°C, the rooting speed drops rapidly.
When the substrate temperature is higher than 35°C, it is difficult for cuttings to survive.
Therefore, the range of 20-35°C is the most suitable temperature for the cutting substrate and cutting bed, and it can also reduce the harm of rot fungi. Moreover, fluctuating day and night temperature conditions are more favorable for rooting than constant temperature conditions. In other words, the existence of a day-night temperature difference is beneficial for the germination of adventitious roots.
Can cuttings be taken in summer?
Why is it not suitable to carry out activities such as succulent cuttings, seedling transplanting, and repotting in summer? Because the average temperature in summer is too high, most succulents enter a dormant period, metabolism has almost stagnated, the root system hardly absorbs nutrients, and most cells also stop differentiating. Activities such as cuttings, seedling transplanting, and repotting will all cause physical damage to the plant, and at this time the callus tissue has already "gone on vacation," and nutrients and auxin have "stopped transport." Therefore, most cuttings cannot recover, let alone grow new apical buds. At this time, the wound surface is usually very easily invaded by bacteria, causing festering. The wound cannot heal, and on top of that it cannot absorb nutrients, so it dies!
However, cuttings propagation of many non-succulent plants can be carried out in summer. This is a difference between varieties. It will not be discussed in detail here.
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