How to increase the humidity in the greenhouse
Not only can the wrong temperature kill the plants in the greenhouse - the moisture level is also important. The simplest indoor hygrometer will help to measure it.
Why can't you deviate from the recommended moisture level for the selected crop? Because when it is lowered, the plants will begin to dry out, and if exceeded, they can rot or become a victim of fungal diseases. In addition, if the humidity is too high, pollen will stick to the flowers, and the ovaries will simply not appear.
However, if you can lower the humidity level in the greenhouse with ordinary ventilation and mulching, then you will have to try to increase it.
Watering paths in the greenhouse
The easiest way to increase the humidity in your greenhouse is to regularly water it. However, this has its own subtleties. If the plants are watered too often, the nutrients will be washed out of the soil, and soon this will be noticeable by the change in the color and shape of the leaves. That is why it is better to water the paths in the greenhouse, and not the ridges themselves, and also to mulch the plantings in order to reduce the rate of moisture evaporation.
It is advisable to water the lanes in the first half of the day, so as not to breed cold night dampness in the greenhouse, which contributes to the development of pathogenic microorganisms.
Steam generators or water sprayers
Another way to solve the problem with the help of technology is to install water sprayers or cold steam generators. True, it is worth remembering that only crops that like high air humidity, such as cucumbers, will like this approach, but for tomatoes it will be unacceptable.
The system itself is installed quickly enough, it works by the clock, but for its functioning it is necessary that you have water constantly available, and not supplied on a schedule, as is often the case in summer cottages.
If you live in the dacha all season, you can simply attach the spray nozzle to a standard irrigation hose and spray the greenhouse with water daily.
It is better to foresee all these measures at the stage of greenhouse construction or before planting, but some of them are never too late to apply. If you notice that your plantings are clearly overheating, hurry to lower the temperature in the greenhouse, otherwise you may be left without a crop.
Changing the color of the leaf to a darker one
Why did the orchid's leaves darken and why is this happening? Sometimes, when buying in the winter, a florist acquires a flower with ordinary green leaves. And after a while he notices that the leaf has begun to darken, but at the same time he does not look sick or affected.
Orchid leaves can darken during the winter season.
If the leaf has not lost its turgor and no foci of damage or harmful insects are found on it, we can say that with the onset of spring, under the influence of ultraviolet radiation, the leaves change their color to a darker one. The flower, as it were, sunbathes under the influence of sunlight. Not to be confused with a burn of the same leaf, when the flower is exposed to the sun and the leaves are simply burned out from the excess of ultraviolet radiation.
In what species is it observed?
Sometimes a dark leaf is inherent in a certain type of orchid, and in the summer, the color of the leaf plate becomes slightly brighter than the winter version. This happens in the following species:
- Ludisia - its variegated leaves have a dark purple hue. Homeland - East and Central Asia;
- Phalaenopsis Schiller - has colored leaves with a red tint. Homeland - Philippines.
External signs
Under the influence of the disease, the color of the plant changes on the leaf plates.Various colors and types of spots may appear on them, which will signal the improper care of the orchid.
Blackheads and spots
The disease is called Urticaria. It arises when:
- High humidity in the room;
- Or frequent irrigation of the leaves;
- And also, if during this period the air temperature is low.
Therefore, oval spots of a dark brown hue appear on the leaves. They initially have a diameter of 3 mm. Later they begin to grow. To cure a flower, you need:
- Cut off the damaged part of the sheet;
- Treat the cut with an antiseptic and fungicide;
- After that, the plant is taken out into a room with warmer air and the humidity is monitored.
Darkened leaf veins
Leaf veins can darken for two reasons:
- Lack of nutrients;
- An excess of nutrients.
Due to the lack of Potassium and Phosphorus, the leaves:
- They stop growing;
-
And they can change their color.
Also, with an overabundance of trace elements, the plant transfers too much mineral fertilizers from the roots to the leaf and the leaf cannot cope with this, getting a burn of the leaf tissue.
IMPORTANT! Apply fertilizers only according to the instructions, without increasing the dose.
Partial or complete necrosis
Leaf cells die when:
- Heat burn;
- Or frostbite in the winter.
To get rid of the stain, if the damaged area is small, then:
- Cropped;
- Treat with brilliant green and an appropriate fungicide.
If the lesion is close to the trunk, then the sheet is removed completely. This will prevent the entire plant from becoming infected.
Wet dark spots
If we exclude that this is the action of ultraviolet radiation, then this is a bacterial disease. The spots spread quickly and destroy the plant. This produces an unpleasant odor. To save a plant, you need to:
- Trim the sheets to a healthy spot;
- And process all sections with trichopolum;
- And spill the plant with a solution of tetracycline 500 mg., Diluting the tablet in a liter of water.
Dark rot in the middle of the leaf plate
This is bacterial rot that appears on the leaves of the plant and spreads through it. To get rid of it, you need to cut off all the blackness to a healthy place and treat the leaf with an insecticide. Spraying is carried out 2-3 times until the threat of plant infection disappears.
If rot appears on the leaves of an orchid, it must be removed.
To prevent this disease from occurring, the plants must be placed freely so that they have access to air.
Watery spots
Brown bacterial rot mainly appears on young leaves due to improper watering. To get rid of this disease:
- The spots are cut off with a sharp disinfected instrument;
- And the cuts are treated with charcoal or a copper-containing preparation.
The disease is contagious to other plants, and therefore the diseased plant must be immediately placed in the quarantine zone until the end of treatment.
Brown or black bloom
Sooty fungus occurs as a consequence of harmful insects such as:
- Shield;
- Or a mealybug.
Therefore, first we get rid of pests by treating the flower with an appropriate chemical preparation - Actellik. Processing is carried out in stages, three times, with an interval of 5-6 days. To get rid of a fungal disease, the following drugs are used at the same time:
- Speed;
- Ridomil;
- Or Mikosan.
Exotic care features
Among the main points to which a person growing a recognizable flower should pay attention are the following:
- priming;
- a worthy place of residence;
- competent watering;
- adaptation period;
- feeding.
A tropical flower is prone to common ailments
Priming
The queen of the tropics cannot develop in ordinary land. Roots need air. Therefore, the substrate must be special. Among the components, the following components must be present:
- coal;
- bark of trees;
- moss;
- fern rhizome;
- Pine cones;
- shells from walnuts;
- peat.
Thanks to this cocktail, close to its natural habitat, the plant will feel comfortable.
Place of residence
The orchid should be surrounded by diffused light for 12 hours a day. If you leave it on a windowsill, which is exposed to direct sunlight, the plant will get burned. A comfortable room temperature is + 23 ... + 25 degrees in the daytime and at least +18 in the evening.
Additional Information. Humidity is an important factor. Its level should be between 60 and 75%. The best solution would be to install a humidifier.
Watering
It is necessary to moisten the soil in a timely manner. Watering can be substituted for the immersion method. The pot, in which holes have been previously made, are lowered into a basin of water at room temperature. Leave for 5 minutes. The procedure is organized once a week and a half during the warm season and once every two weeks during the cold season.
Top dressing
Exotic should be fertilized with special dressings. Purchase them in specialized stores. Activities are carried out strictly according to the instructions. Some mixtures can be used every 60 days, some - once every 3-4 months.
New plant is quarantined
How to deal with spotting: step by step instructions
On the leaves
Depending on the disease that led to the development of spotting on orchids in the area of the leaf plate, there is a specific method of treatment:
- Hives. To combat this ailment, it is necessary to increase the air temperature in the room and lower the humidity level to 50-70%.
- Late blight. It is no longer possible to save a plant that was struck by late blight, so you will have to say goodbye to it. But there are several rules that will help to avoid the development of the pathological process:
- do not increase the humidity of the air;
- make sure that the room is warm;
- do not leave drops of water on the flower areas.
- Powdery mildew. For the treatment of an orchid, it is necessary to spray it with Scor or a solution of colloidal sulfur. Only at the beginning of therapy, water the flower thoroughly, and after 2 hours proceed to processing.
- Rust. The method of treating this ailment is similar to those given above. Remove the affected areas immediately, and treat the cut with a 25% alcohol solution. The following spray preparations are used to treat a flower:
- Mikasan;
- Speed;
- Ritomil.
- Rot. If the plant has been affected by rot, then it will have to be sprayed with a fungicide. With a secondary lesion, it is already worth using another drug, since rot spores quickly adapt to the means used.
On flowers
Spots on the leaves of the bud are the first signal that a fungal or bacterial disease has struck an orchid. It all starts with the yellowing of the foliage, which darkens over time and becomes elastic. Then the petals are covered with moist ulcers, from which a liquid substance flows.
To save flowers from this infection, it is necessary to cut off the affected petals, and treat the cut sites with iodine. More potent drugs can be used. But to do this in case of neglect of pathology.
Reference! If, after 2 weeks after treatment, new spots have not appeared on the buds, then the plant is no longer infectious and can be removed from quarantine.
Why do the leaves of an orchid turn black?
If black spots appear on the plant, you need to find out the reason for their appearance in order to save your flower. The disease can affect any varieties of orchids (Cattleya, Dendrobium, etc.). For this, the florist must carefully examine the leaves of the plant.
Unfavorable conditions of detention
Most often, blackness is caused by improper content, namely, from frequent flooding with water, the leaves begin to rot. Also, blackness occurs if in the room:
- Very dry.
- High humidity at low air temperatures.
- When overheating in summer, when the ambient temperature is above 30 degrees.
- With hypothermia in the cold season, since temperatures below 16 degrees cause frostbite.
- When a flower is infected with a tick.
If the reason for the appearance of spots is improper care, it is necessary to urgently change the conditions of detention and treat the plant with foundation.
IMPORTANT! If the flower has been inappropriate for a long time, this can lead to bacterial and fungal diseases. In this case, the treatment will be longer.
Irrigation irregularities
When the watering regime is unbalanced and it is done too often, then due to constant waterlogging, black spots appear on the leaves, which grow over time until they merge into one spot.
This is often caused by moldy fungi, which tend to thrive in damp conditions at elevated temperatures. These mushrooms lead to fusarium wilting.
Therefore, if possible, it is worth trimming or cutting out all black spots and waiting until the cuts are healed, and only then treating with an appropriate fungicide.
IMPORTANT! When treating a plant, it is quarantined and after 2 treatments it is kept for at least 2 weeks.
Hypothermia of a flower
When the plant has received hypothermia, then black weeping spots appear on its plates. You need to get rid of them by cutting off the affected part of the sheet.
If the leaf is completely affected, it is removed by cutting the tip of the leaf in the middle and pulling them in different directions. This method ensures that everything is lifted from the base of the plant.
You can supercool:
- Carrying a flower in the cold season without proper insulation;
- Keeping the flower in a cold room.
IMPORTANT! In order not to heal, hypothermia must be avoided.
Bacterial and viral infection
All three diseases described below are caused by bacteria or viruses that can appear as a result of improper care. First of all, it is necessary to remove the plant away from others, since these diseases are contagious.
Fusarium
Fungal disease caused by spores of Fusarium fungi. The spot on the leaf will be slightly convex, after which the leaves in the affected areas crumble into dust.
Often, mushrooms appear due to frequent excessive flooding. Therefore, proper watering will guarantee the absence of this disease.
Fusarium orchid.
Septoriasis
Septoria selenophomoides bacteria carry diseases. In this case, the stains are first wet and then dry and turn black.
If you do not start treatment, the number of spots increases due to the multiplication of bacteria and they merge into one black spot with a yellow dry border.
Septoria.
Black spot
It is a viral disease that can be identified by various black spots, streaks and dots. The disease spreads quickly and it is necessary not only to move the plant to the quarantine zone, but also to cut off the damaged leaves.
It develops if the room has a high ambient temperature and high humidity. Plus the lack of fresh air.
Black mosaic
A viral disease that can be identified by black spots, which are subsequently perforated. The flower can get this disease through mechanical injury. Also, harmful insects that carry this virus on themselves can help with this.
Black spots on orchid leaves
Black spots can be caused by:
- A thermal burn can be heat from a radiator or a stream of steam from a kettle. Such spots cannot be treated, you just need to prevent both heat and sun burns of the plant;
- Black spot - the disease is transmitted with the help of fungal spores and, in order to get rid of it, it is necessary to apply fungicides and normalize the conditions of detention, in particular, watering and air humidity, which should not exceed 80%;
- Bacterial Spot - As the name suggests, it is a contagious disease caused by bacteria. The plant must be immediately isolated from the rest. Treatment is carried out with antibiotics and bactericides.
IMPORTANT! Before starting treatment, the first step should be to quarantine the flower.
A separate article is devoted to the fight against black spots on our website.
Orchid treatment
The treatment of a flower butterfly, as the plant is sometimes called, is mostly a laborious process. The owner of the flower must be ready to fight for the life of his pet. Thanks to the advice of experienced florists, various ailments can be dealt with at home.
Dark spots
How to cure an orchid if dark spots appeared on it, and it got sick with late blight, chlorosis? The very first step is a moderate feeding with iron chelate. Next, the affected leaves are removed with a sharp knife rubbed with alcohol. Places of cuts are sprinkled with fly ash. As soon as the slices begin to tighten, the plant is treated with fungicides. For example
- Alerin;
- Mikosan;
- Bordeaux mixture;
- copper sulfate;
- Quadris, etc.
Additional Information. Fungal diseases, which also appear as dark spots, are treated with copper medications.
Brown rot
This is a bacterial disease. The infected plant is placed on a free windowsill so as not to infect neighbors. Damaged areas are removed. After a couple of days, the flower is treated with Bordeaux liquid. The procedure is repeated every 20-35 days.
Powdery mildew
Fighting the disease at the initial stage is not difficult. The plaque is wiped off with a cloth soaked in soapy water. The solution is prepared from warm water and laundry soap. Further, the means are applied:
- Speed;
- Topsin-M;
- Fitosporin, etc.
Fungicide Skor
White bloom
How to treat white sticky plaque on an orchid? Parasites are removed in a complex manner. The plant is isolated, the affected parts are removed, and the soil is changed. The flower is sprayed with Fitosporin or Aktara, Calypso.
Anthracnose
Anthracnose is treated by removing damaged leaf plates. For this, a disinfected sharp knife is used. Places of undercuts are sprinkled with ash.
Rust
The initial stage of rust is treated in the same way. Damaged leaves are cut out, places are treated with ash.
Information! For reliability, the entire plant can be sprayed with Mikosan.
Foliage stickiness
If there are no other signs besides the usual stickiness, then the flower is placed on the windowsill, where there is more light. You can install additional lighting lamps above it. The room is thoroughly ventilated, but drafts are not allowed. The leaves are treated with antibacterial drugs. Suitable:
- Maksim;
- Fitospirin;
- Sutomai.
All orchid diseases are a nuisance for the grower. To prevent ailment, you need to provide the plant with proper care. If it starts to waste away, gets sick, the first thing to do is to determine the disease. After that, treatment begins. At the same time, it is impossible to start the disease. The sooner the treatment starts, the sooner the tropical beauty will come to her senses.
Root rot
Keep in mind that the roots can be affected by both rot and fungus. Often they are affected by such types of rot as:
- Gray. It affects both roots and leaves. You can determine the presence of a problem by dark areas with a bloom of gray in different parts of the plant. Often the problem is with the leaves. After them, the soil, the roots, and the flowers suffer. The cause of rot is high humidity and low room temperature. Excessive use of fertilizers with an increased concentration of nitrogen can also affect the appearance of gray rot. Keep in mind that gray mold is a fungus. If stains are found, remove all affected areas by cutting out, and spray healthy areas with fungicides. When reappearing, you cannot use the same drug, you need to select another. The appearance of gray rot is typical for cattleya, phalaenopsis, cymbidium and other varieties of orchids with white flowers. For prevention, when watering, you need to use drugs to increase the resistance of orchids to diseases, in addition, do not put the orchids close to each other.
- Root.It appears on the roots of the plant. They become soft and die off over time. Brown leaves are another indication of the presence of the disease. Root rot is caused by high temperature and humidity in the room. If you have already seen the problem, spray the roots with a solution of foundationol (0.2%) or topsin (0.2%). Repeat the procedure three times every 20 days. The disease often includes cymbidium, miltonia, and pafiopedilum. Prevention can be the use of a quality substrate.
All of these orchid root system problems are considered the most common. Moreover, in most cases it is possible to cope with them. The main thing is to notice the problem in time and quickly start treatment.
Some phalaenopsis diseases can be caused by a containment breach
Inspect the plants regularly, this will help to identify pests in time and start treatment.
Improper lighting affects the development of the plant. When buying a flower, be sure to find out what type of orchid you purchased. They are shade-tolerant and light-loving. None of the phalaenopsis species tolerate the open sun and can burn the leaves.
When watering orchids, the rule applies: it is better to underfill than overflow. But be careful, because with too dry air and poor watering, the orchid may shed its leaves, or sticky drops may appear on them. High humidity will contribute to the appearance of fungal and bacterial diseases. Low or too high temperature also does not contribute to the normal development of the plant and can cause the appearance of fungal diseases. Buying orchids in the cold season may cause frostbite on the leaves.
Types of pathogens
There are three main groups of plant disease pathogens: viruses, bacteria, and fungus.
Viruses
Defeat with a viral disease poses the greatest danger to a flower culture. In most cases, this leads to the death of the indoor plant.
An ailment appears along with pests - mites, nematodes, scale insects, which are distributors.
In this case, the development of the infection passes without pronounced symptoms. Indicates damage is only a change in the color and shape of the vegetative mass of the orchid.
The tool used for leaving is also capable of infecting a home flower. Factors contributing to the reproduction of viruses: temperature drops, a decrease in immunity in a flower culture.
Bacteria
Diseases of bacterial etiology lead to decay of the root system and blackening of the vegetative parts (at an advanced stage, this ends with their death). The most common are Ervinia, which causes wet rot, and Acidovorax, which attacks foliage.
Often, a bacterial infection develops with mechanical damage to the vegetative mass.
Fungi
Fungal diseases do not develop as rapidly as bacterial ones, but they are characterized by increased resistance to the action of fungicidal drugs.
It spreads by sporulation, the fungus spreads with air currents contaminated with the substrate.
Means of struggle
Aktara
The drug destroys aphids, whiteflies, thrips, scale insects, false scales, soil flies. In Aktar there is thiamethoxam, it completely eliminates pests.
Thiamethoxam completely decomposes in the soil, dissolves in water, is absorbed by phalaenopsis from the ground. Aktara affects the digestion of parasites, they immediately stop feeding on the orchid.
Aktara effectively and quickly destroys pests.
Pour 4 g of the drug in 5 liters of water, and then use it. You can put the flower pot in this solution for a few minutes, or you can spray the leaves and water the substrate with the solution.
Aktar can be easily mixed:
- With zircon;
- Ribav-ekstroy;
- Epin.
Actellik
Actellik is considered to be an analogue of the Bi-58 drug, which is prohibited from using in Russia.
In Aktellik there is pirimiphos-methyl.Sold in cans of 3-5 liters, in ampoules of 2-5 ml, which are filled with a concentrated emulsion, in the form of a wettable powder.
The parasites die within 10 minutes to several hours.
The composition destroys: aphids, thrips, scale insects, whiteflies, caterpillars, various mites, mealybugs.
Actellic is classified as a hazard class 2 drug.
Use only freshly prepared solution. Pour an ampoule with a volume of 2 ml into 2 liters of water.
If there are a lot of parasites, then dilute 1 ampoule in 1 liter of water. Treat the plant on the loggia.
Moisten the entire surface of the orchid leaves and stems with the solution, then pour under the root.
After a week, do the treatment again.
Cover the treated orchid with a plastic bag, put it for 1-2 days in a well-ventilated room, which you do not go into.
Actellic is incompatible with Bordeaux liquid and products that contain copper.
For treatment with the drug, wear special clothing, gloves, a respirator, and goggles.
Do not eat, smoke, or drink when spraying with phalaenopsis.
Then remove the overalls, wash all exposed parts of the body with soapy water. Rinse your mouth. Eat a few activated charcoal tablets and drink milk.
Put the packaging and containers in a polyethylene bag, tie, burn. Break the ampoules before that.
If required, the antidotes for Actellic are atropine sulfate, R-AM.
Fitoverm
It contains aversectin C, it is obtained from a soil fungus.
Fitoverm destroys ticks, thrips, scale insects, aphids, mealybugs.
To destroy parasites that multiply on phalaenopsis, dilute 1 ampoule in 0.5 liters of water. Do 4 treatments at intervals of 10 days, as the drug will not eliminate the larvae.
In addition, spill the potted substrate with phytoverm solution.
The main advantage of Fitoverm is low danger to humans.
To eliminate the mites, remove the phalaenopsis from the pot. Destroy the pot itself. The plant will lie quietly for a week without a substrate.
Wash the orchid roots thoroughly with hot water, then dissolve 1 mg of phytoverm in 1 liter of water, treat the plant. Use only freshly prepared solution.
Cover the orchid for a day with a plastic bag. Put the bag with the culture in a bowl, place in a place illuminated by the rays of the sun.
After 10 days, do the treatment a second time. Then rinse the roots with hot water and plant in a new pot.
After 5 days, water the plant with water.
Agravertine
It is a transparent emulsion placed in 5 and 10 ml glass ampoules. Parasites do not adapt to the drug.
Agravertine destroys ticks, aphids, thrips. It paralyzes larvae and adults, they cannot feed, and then die.
The drug acts on insects for 2-6 days. To treat phalaenopsis, pour 5 ml of the drug into 2.5 liters of water. Process by transferring the plant to the bathroom, to the loggia. Spray the entire plant with a sprayer.
Wait for the orchid to dry, place it in the sun, but not in direct sunlight.
Advice! If there are a lot of parasites, then repeat the treatment after a week.
Prophylaxis
Take a good look at your new copy.
It is important to know everything about him:
- The name of;
- What he loves;
- What he doesn't like;
- That just suffers;
- For all seasons.
And follow the recommendations for growing it:
Take care of the lighting. He needs it at least 12 hours. And in winter too. Install additional lighting if necessary. And turn it towards the light source after a couple of weeks. Do not do this when buds appear;
Install thermometer
It is very important not to exceed 25 degrees in summer. And in winter it did not fall below 17-18 degrees
The temperature amplitude per day should not be more than 7-8 degrees. My friends put it on the balcony in the summer. It blooms beautifully;
Be careful with watering. Adhere to the rule - after watering, the substrate should dry out to the bottom. The green color of the roots indicates the correctness of the actions.Immerse in prepared warm water for twenty minutes. Place on a wire rack. For the water to run away. And the water can be melted, rainwater and distilled. Tap water will quickly finish off the plant;
One thermometer is not enough. It is also necessary to measure the humidity of the air. But first create the required one. It should not fall below 40%;
Attention! Very important! Watch out for the axils of the leaves. Water should not accumulate there. Then problems cannot be avoided! Spraying indoor air is more advisable than the plant itself
And after watering, wipe the leaves dry.
Then problems cannot be avoided! It is more advisable to spray the indoor air than the plant itself. And after watering, wipe the leaves dry.
- I will not say how he is fed in his native places. I doubt that they do it there. And you just need it. You can "Kemiroi": 1 g per 1 liter of water;
- The soil is specific. It is easier to buy in special stores than to make the appropriate proportion yourself from bark, charcoal, sphagnum and perlite;
- Transplantation is a separate topic. Determine the right time. But not the flowering period.
So there will be healthy flowering plants. With beautiful flowers and leaves.
Root diseases and flowering problems
Diseases of the roots cause problems with flowering, but we will talk about diseases of the root system later, but weak flowering is a problem that is often encountered. The main reasons for the lack of buds are as follows:
- improper watering;
- sudden changes in temperature;
- violation of the rest regime;
- insufficient lighting.
Another problem is that buyers forget to check with the seller what kind of plant they purchased and how exactly it blooms, as well as generally find out the description of the plant.
It is important to understand that different types of orchids produce buds and bloom at different times of the year. It often happens that the owner is looking forward to the first flowers, but only the green mass grows
How to understand that an orchid lacks light? This is not difficult
Pay attention to the color of the leaves. Natural shade - soft green, light and even slightly muted
Bright green tones are a sign of a lack of lighting. If the leaves turn yellow, then this is a signal that an excessive amount of ultraviolet radiation is getting on the plant.
What to do in a similar situation? Place the plant either in a more illuminated place (in the case of bright green leaves - a vivid example in the photo), or in partial shade (if you notice yellowness).
An equally common reason for the lack of peduncles in orchids is root diseases. It is very difficult to identify this problem, especially if the plant is already in bloom. The latter can be observed even in the case of root rot. But if the plant does not please with either flowering or buds for a long time, it's time to check the root system. Rot (most common) is caused by over-watering. Remember to bathe the plant in a bowl of water for 20-40 minutes once a week. This flower is enough. But you do not need to fill it with water so that it stands in the pot.
What to do in a similar situation? The best solution is to transplant the flower into a new pot and remove the damaged areas of the roots. In principle, transplanting is useful as a periodic occurrence in plant care.