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The requirements for light in cacti are special, unlike other indoor plants, cacti never have a lot of light. True, some cacti require direct sunlight, while others require bright, intense, but diffused light.
Some types of cacti need direct sun all the time, even in the hottest hours of the day, some types require shading from 12 to 15 hours on sunny summer days in the form of a light mesh. If the day is not sunny, the net should be removed. This has its own difficulty, since from morning to noon the cactus should be in intense light, and when the sun begins to bake at lunchtime, you need to arrange shading. As soon as the rays fade a little, the shading is removed. All this applies to the option when the cacti are on the south window. Shading is usually not required on the west and east windows.
Starting in September, sometimes earlier, shading is not needed even on the southern window, the sun is already low enough, the days are shortening. The winter sun never leaves burns on cacti, and if there is no cold wintering, then the sun is sorely lacking.
Placing cacti on the window is very important: pay attention to the photo, such a setting steals light from the plants, all the light passes over the tops, the main part of the cacti does not catch the sun, because the frame covers it. It is necessary to raise the cacti on a stand so that the whole body of the cactus is well lit.
Under natural conditions, in autumn and winter with a natural decrease in the intensity and duration of the sun, the air temperature drops and stays slightly above zero. All life processes in the cactus organism freeze, it goes into a state of rest. In spring, with lengthening daylight hours and the simultaneous onset of warm days, cacti resume growth, often blooming at the same time.
Our pets expect the same conditions from us. They need a cold rest period! If you do not rearrange them in a cooler room (from +5 to + 15 ° C for different species), then the cacti will continue to grow, if at the same time the lighting is not maintained at the appropriate level, their stems are stretched, tilted in one direction - they stretch towards the light, and disfigured. Many cacti never bloom for 3-4 months without a winter dormant period.
The photo shows how I placed the cacti on the glass shelves. Three sheets of glass of the same size are suspended at different heights on strings, which are fixed with hooks in a wooden frame or above a window opening (anchor hooks). This allows the pots to be placed as close to the glass as possible and the glass shelves steal less light. If the pots were on the windowsill, they would have to be arranged in rows, and those in the back rows would receive less light.
Signs of a lack of light
If the top of the cactus begins to stretch and thin out, it means that it lacks light. I brought such a freak from a computer class. The wavy body of the cactus shows that at times the sun fell on it - in these happy times, its body developed in width. But then the poor fellow was again put to the next monitor, far from the window, so that he could catch the "harmful" radiation, and he became thinner, because in warm room conditions he continued to grow with watering.
It is worth remembering that pollution - dust, dirt and streaks from rain greatly delay lighting. You need to wash the glass several times a year both from the inside and from the outside, because even after spraying the plants with clean boiled water, stains remain on the glass.
Sign of excess sun
There are also cacti, although there are few of them that cannot tolerate the sun's rays in a wider range of the day - they need shading from 11 to 17 hours - these are mainly epiphytes and semi-epiphytes (Ripsalis, Schlumberger, Epiphyllum). But this rule applies in central Russia for the period from March to August, and from about September to February the direct sun does not threaten them.
Any cacti need shading if they have just been transplanted (within a week or two) and when the cacti are sick. In the spring, after a long winter that is stingy on sunny days, cacti should be gradually taught to the bright sun.
If the sunlight is too intense, the stem of the cactus, its skin becomes reddish or slightly purple. It looks like a tan and is not a permanent defect. If you re-saturate the cactus to a more diffused light, the redness will disappear. But in forest cacti (epiphyllums or Decembrists) from the excess of direct sun, the stems first turn red, but if not shaded, burns can form - oblong dry spots, usually whitish or gray. This usually happens on the southwest windows.
If a tan appears on cacti, this is generally not even a reason to create shading, it all depends on the type of cactus and its requirements. Many cacti in nature under the scorching rays of the sun not only turn red, but slightly wrinkle, but at the same time bloom wildly, literally covered with flowers.
It is better to use a mosquito net or organza as shading. If your cacti are located on the south window, which is not shaded by anything from the street, then you can pull the string along the glass (as is usually done in kitchens) and hang a piece of tulle. If you leave for work and see that the day will be hot, then curtain the window in the morning.
Artificial lighting of cacti
Oddly enough, but children of deserts can be grown even completely under artificial lighting. Of course, this is an extreme case when you really want to grow thorny pets, and the windows are either very dark (northern, shaded with trees from the street, the first floor) or at work, where there are no windows at all. But usually in such conditions supplementary lighting is required all year round both in winter and in summer, only the intensity depends on the temperature: the cooler the content in winter, the less need for supplementary lighting.
If you are going to grow cacti from seeds, then you cannot do without additional lighting - so that the seedlings do not stretch, they need a lot of light.
What lamps to use for artificial lighting of cacti
Plants need light of a certain spectrum, not at all what we see. The plant needs blue light for the growth and development of roots and greenery, orange-red for the development of leaves and flowering. It is on this fact that special phytolamps are designed. There are fluorescent phytolamps and LED ones. The difference in energy consumption - LEDs consume less, but lamps are much more expensive than all others.
Craftsmen versed in electronics, able to design supplementary lighting for their plants on their own. They make lamps, connect blue and red LEDs, and collect metal halide lamps. But what to do to mere mortals who do not think anything in electrics? We do it simply - we buy ordinary fluorescent lamps. Now such lamps are available with a conventional E27 base, with a narrow E14 base. But we need lamps with an improved (above average) color rendering index. These have the Russian LBC nomenclature, on European lamps the designation is 865 light color. It is designated as follows: "Color: Day Deluxe 865" or "Color Code: 865 (Color Temperature 6500K)".
In the people, such lamps are affectionately called lumkas. So, the main thing for the hatches to be effective is a sufficient number of lamps. The distance to the tops of cacti or seedlings is no more than 5-7 cm, otherwise the cacti will stretch. The distance between the lamps depends on the shape of the lamp. If under a conventional cartridge, then after about 20-30 cm, depending on the power, if the tubes, then the distance between in parallel is 5-7 cm. To increase the efficiency of the lamps, reflectors can be made. For example, instead of a cardboard lamp shade, bend the collar and glue it with foil from the inside.
Fresh air for cacti
Fresh air is much more important for cacti than for most other plants. Many cacti may fail to bloom just because they lack fresh air. Therefore, for the summer, it is better to place them on a balcony or veranda. At the same time, care must be taken that they are protected from dust, wind and rain. If the balcony is glazed, then the cacti are provided with shelter and fresh air, and if not, then you can make a canopy above the shelf with cacti from light-transmitting material, for example, from a greenhouse film.
If there are a lot of cacti, then it is best to arrange the pots on one common tray, so they are easier to carry. Ideally, it would be good to gradually accustom the cacti to the street, and leave them until the end of summer and even until the beginning of autumn around the clock in the fresh air. Accustoming cacti to nighttime temperature changes helps to strengthen the skin on the plant stem, the hardening procedure prepares it for cold wintering. Such cacti are distinguished by shiny thorns, bloom better and more easily and have greater resistance to disease. However, for all the love of cacti for fresh air, drafts can be disastrous for them
When there is no balcony or veranda, you still need to find a way to provide the cacti with as much fresh air as possible. As far as possible, keep a window or window open, while avoiding cold drafts.
Of course, if you have patience and skillful hands, you can make a shelf behind the window. Those. attach something to the windowsill from the street, on which you could put trays with pots of cacti. You can assemble a low wooden box to fit the window sill and fasten it tightly. True, besides this, you will have to take care of shelter in case of rain or strong wind.