Light, temperature, humidity, water, nutrients, and soil all have an impact on plant growth.
Ample light is by far the most crucial factor influencing plant development in interiors. In general, the more light that is available, the more food that is created for growth. Light is necessary for plants to produce food and survive. Foot candles are the units used to measure light. A footcandle (ft-c) is the amount of light a candle casts on a white surface when it is placed one foot distant from it in a pitch-black environment. On a beautiful day outside, the light levels range from 10,000 ft-c in an open location with plenty of sun to 250 ft-c or fewer under a big tree.
Knowing the general amount of light that is present in a certain area of your home is quite helpful. With a handheld light meter, you can obtain a decent approximation, or you can use a 35 mm camera and carry out the following steps:
- Set the shutter speed to 1/60th of a second and the film speed indicator to ASA 25.
- Place a piece of white paper where you wish to measure the light levels, point the camera at the paper from a distance that allows the paper to fill the view, and change the f/stop until the meter reads the proper exposure.
- Read Table 1’s approximate light level.
You can use this table to get a reading of the light intensity from anywhere in your house. For instance, if the f/stop is set to 16, the light intensity will be roughly 2,400 ft-c.
Your home can be separated into four regions using the light readings, each of which has the following light levels for eight hours each day:
- Low-light conditions: 25 ft to 75 ft
- 75 feet to 200 feet in situations with medium light
- places with high lighting (above 200 ft-c), but not in direct sunshine
- places with plenty of sunlight: at least 4 hours of direct sunlight
Figure 1. Native to tropical rain forests with low light levels are several foliage species. If exposed to intense light, these plants are readily damaged. Upright leaves and browned, burned leaves are signs of overexposure. Avoid placing high-light-sensitive plants in the sun’s direct rays (on a porch or in front of a window). In this illustration, high-light damage may be shown in Chinese Evergreen (Aglaonema) and Dumb Cane (Dieffenbachia) symptoms.
In your house, light levels vary depending on where you are.
It is impacted by the presence of trees outside (which may provide shade at certain times), roof overhangs, the color of the walls (which may reflect light), the existence of window curtains, the length of the day, the time of day, and the season.
When choosing indoor plants, consider the approximate light levels in the area before making your choice. Information on the plant’s light needs is typically included on the label. The use of artificial light sources like fluorescent and/or specialized incandescent lights can be utilized to complement natural light when a plant’s label indicates that it should be “high light,” but the chosen area of the house does not have enough light.
Increased light exposure, such as 16 hours of light and 8 hours of dark, can also be beneficial. This increases the amount of time that plants are exposed to light.
While sufficient light is essential for plant growth, excessive light can be harmful (Figure 1).
The type of indoor plants differs depending on how much light they require to flourish. (Table 3 provides a list of plants along with their light requirements.) Generally speaking, look for the following details on the plant’s label:
- Low: 25 ft-c75 ft-c minimum, 200 ft-c 75 ft-c for optimum growth
- Medium: preferable 200 ft-c500 ft-c, minimum 75 ft-c150 ft-c
- High: 500 ft-c1,000 ft-c is ideal; 150 ft-c1,000 ft-c is the minimum
- Very high: 1,000 ft-c or more is preferred as a minimum.
Because plants receive direct morning light from sunrise to almost midday, windows with eastern exposure often offer the greatest lighting and temperature conditions for most indoor plant development. These windows’ footcandle values might range from 5,000 to 8,000. The direct sun leaves the room as the morning goes on.
Because the house absorbs less radiant heat, an eastern room is cooler than a southern or western room. Compared to light coming from the south or the west, eastward light is cooler, which results in less water loss from plants.
The most variance in light and temperature is found in windows that face south. The majority of the day is spent with the low winter sun shining across the room.
The sun rises at a sharp angle in the morning and is high in the sky by noon in the summer, when it is farther north than it is in the winter. Only at midday does direct light enter a south window. The sun might not even shine inside the room if there is a large overhang covering the windows on the exterior. On a hot day, the sun’s height at noon may be 10,000 ft-c. However, a southern window inside with large outside eaves will get about the same amount of light as a window facing north. For the majority of plants, southern and western exposures are equivalent. Most plants can be placed in a room with southern exposure in the winter, with the exception of those that have a clear preference for northern exposure.
The windows that face north let in the least light and have the coldest temperatures. The majority of the sun’s rays reach the United States from the south because it is located in the northern hemisphere. The northern exposure receives the least amount of heat and light out of the four exposures.
Figure 2 shows how the seasons affect how much natural light enters your home.
It can be difficult to keep healthy plants because of the lack of light. On a clear winter day, a northern windowsill can measure light levels as low as 200 ft-c, which is ideal for some plants, such the African violet. Because variegated foliage tends to lose its pigment in low light, plants with green foliage benefit most from this exposure. While most indoor plants won’t thrive in a northern room, some might withstand it for a short while.
The amount of natural light that enters via windows varies with the seasons. For instance, the summer sun rises higher in the sky than the winter sun (Figure 2). As a result, in the winter, more light enters a room.
- The plant is unable to grow.
- Internodes, or the spaces between leaves, are much longer on the new growth than they are on the plant’s older growth.
- Compared to the elder leaves, the young leaves are smaller.
- On the fresh foliage compared to the older foliage, the leaves are a brighter shade of green.
- Older leaves are already dead.
In interior conditions, temperature is the second most crucial factor affecting plant development. Because the majority of indoor plants come from tropical and subtropical regions of the world, people feel most comfortable in a range of 72 degrees F to 82 degrees F, and indoor plants can withstand and thrive in a range of 58 degrees F to 86 degrees F.
Through the processes of photosynthesis and respiration, temperature and light are related. You might think of these processes as the “yin and yang of plant life”—two halves of a circle. Sugars and starches are created by photosynthesis and then broken down by respiration to produce energy for both the formation of new tissues and the upkeep of existing ones. Respiration is accelerated by high temperatures. High temperatures may break down any sugars that are produced if the plant is not producing enough (as in low light situations), leaving little or no sugars for growth. Because maintenance comes before growth, plants cannot grow under low light conditions. The plant eventually perishes if the amount of light is so low that the sugars generated are insufficient for maintenance.
In order to retain new leaves when sugar levels are low, the plant absorbs nutrients and sugars from older leaves. There are two ways to assist plants in an indoor setting: Either (1) increase light levels to boost photosynthesis and sugar production, or (2) decrease nighttime temperatures to slow respiration and promote the growth of additional sugars.
What kinds of temperatures are most common in homes? In the summer, higher-than-desirable nighttime temperatures are caused by air conditioning that may have been left off at night or thermostat settings that may have been increased over the weekend. Lower nighttime temperatures may occur throughout the winter if the heating has been switched off at night or if thermostat settings have been adjusted during the weekend. Avoid allowing temperatures to fall below 50 degrees Fahrenheit as this could cause chill damage to some delicate foliage plants (e.g., Chinese Evergreen, Aglaonema). Lower leaves begin to yellow and/or lose their leaves as a result of chill damage.
The minimum and maximum temperature needs for plants differ. Cyclamen, Wonder Plant, Fatshedera, Japanese Aralia, and Fatsia are a few examples of cool-loving plants ideal for areas where daytime highs are in the 60s and lows are in the low 50s. Table 3 gives a list of plants together with their temperature needs.
Different indoor plants require different temperatures for optimum growth. For instance, ferns, Cast Iron Plant, and Aspidistra really grow better at cooler temps (72F), whilst other tropical plants thrive at temperatures between 90 and 95 F. Rarely are such temperatures permitted indoors.
The ideal temperature range for indoor plants is 70°F–80°F during the day and 65°F–70°F at night.
The amount of moisture in the air is measured as relative humidity. Relative humidity is measured in percent, with 20% being low, 40% being medium, and 50% being high for indoor plants. Although it is simple to ignore, relative humidity is a highly significant component. Relative humidity is at least 50% in a greenhouse. When newly purchased plants are kept at the average 10–20 percent relative humidity of most houses, rapid transpiration and water loss may occur (Figure 3). The majority of houseplants are native to the tropics, where high relative humidity is typical. To assist your plants in adjusting to the low relative humidity in your house, take the following actions.
Image 3a. More water is lost from a leaf the lower the relative humidity. A leaf placed in an environment with 10% relative humidity loses more water than a leaf placed in an environment with 50% relative humidity at the same temperature of 70%F.
Image 3b. The more heated the air is, the more water vapor it can carry, and the more water the plant will lose. A leaf placed in 90°F air loses more water than a leaf placed in 70°F air at the same humidity level of 50%.
- To produce a microenvironment with a greater relative humidity, group plants closely together.
- Use a small container filled with water and lava rocks or gravel to raise the relative humidity by allowing water to evaporate from a vast surface area.
- Apply a humidifier.
- Spray water with mist bottles around the plant; but, in fact, you would need to mist continuously for an extended period of time to noticeably change the relative humidity around the plant.
- Plants with hairy leaves should not have water sprayed on their foliage or blossoms. Such leaves may retain water for a longer period of time, giving disease spores the chance to sprout.
One of the most crucial aspects of caring for plants is knowing how to water them. Too much watering can smother the roots of plants, and not enough watering stunts and inconsistent development. The frequency of watering will vary depending on the growing circumstances for the plants. When determining how much water to use, take into account the following:
- Type of plant: Table 3 provides a list of plant types along with their moisture needs. The amount of water that different plants require varies. On the plant label, along with the preferred light, this information is typically present. For instance, crotons, which favor high light levels, will probably require more regular watering than succulent plants like Opuntia cacti. Both require the same amount of light, but different amounts of water.
- Plant size: In comparison to smaller plants, larger plants require more water.
- Container volume: Watering may be necessary more frequently if the growing container is too tiny.
- Moisture in the soil: How much water is already in the growing medium will also influence how frequently you water it.
- Light level: Under comparison to plants in low light, high light plants transpire more water.
Numerous issues arise from improper watering. Saucer-style containers could result in an excessive buildup of soluble salts (from the applied fertilizer). High concentrations of soluble salts can harm plant roots and slow growth. Apply a lot of water to the soil to leach the accumulated soluble salts. Discard any water that had collected in the saucer after irrigation. Pushing a finger about an inch beneath the surface will allow you to feel the soil and determine when to water. There is no need for additional water if the soil is still wet. To make watering easier, there are also water devices and water meters available.
Plants that are sensitive to fluorine and chlorine, such as Corn Plant (Dracaena), Ti Plant (Cordyline), Peacock Plant (Maranta), and Rattlesnake Plant (Calathea), provide a problem with the irrigation water’s quality (Figure 4). Allowing the water to rest for a few days may help to release some chlorine and fluorine before you apply it to the plants, which will help to solve this issue. To stop water splashes from damaging the foliage, move plants that are vulnerable away from the edge of the pool. Useless plants should not be present near enclosed pools. Fluorine sensitivity is generally higher in plants with long, linear leaves, such as the spider plant.
Figure 4a shows leaf and tip scorching as fluorine damage symptoms in corn plants.
Figure 4b shows leaf and tip scorching as fluorine damage signs on the Ti plant.
Many indoor gardeners struggle with giving their plants too much fertilizer, just as they do with water. Any fertilizer used, whether in liquid, powder, or tablet form, will breakdown in soil water and create salts in the water, posing a risk of overfertilization. The water in the soil becomes so salty when you over-fertilize that it “burns the plant’s roots by taking water from them” (Figure 5). Excess soluble salts build up as a yellowish crust on the growing medium’s surface and/or close to the container’s rim.
Figure 5a: Leaf martini and tip burn are symptoms of soluble salt burn. Dead roots also encourage root infections.
Figure 5b. Soluble salts can burn roots; notice that the healthy roots are white, while the dead roots are brown. Dead roots also encourage root infections.
Prior to feeding plants, take into account the following:
Ficus species, for example, are strong feeders, whilst other plants require little to no additional fertilizer over the course of months (e.g., succulents). Smaller pots need less fertilizer than larger ones since they have less soil in them, which is the growing medium that is present. Light levels: More nutrients are required for plant growth at increasing light levels.
Rarely does a newly acquired, healthy plant require fertilizer right away. The amount of fertilizer used by the industrial farmer will often be sufficient to supply the residence with nutrients for two to three months. This guideline is supple. Fertilizer application is preferred if deficient signs are noticeable.
Applying modest amounts of fertilizer as the plant grows is the key to fertilizing indoor plants. The plant’s requirement for further fertilizer is minimal without new growth. A plant need less fertilizer in the winter when there is less light. The plant needs more fertilizer in the summer because of the increased light levels and active growth. Use around one-fourth of the label rate as a starting point for monthly applications. Fertilize every two weeks if the overall plant color starts to turn lighter green. Reduce the fertilizer rate if the new growth is dark green but the leaves are tiny and the internodes appear to be longer than on the older growth.
For indoor gardeners, a variety of fertilizer mixes are available. Many fertilizers are available in formulae that are specifically made for indoor plants. To avoid overfertilization issues, they often include a smaller percentage of the necessary mineral components.
A growth medium offers minerals, water, and anchoring. When repotting plants, make sure the new mix is properly pH-balanced, well-drained and aerated, and holds water and nutrients effectively (5.0-6.5). The root system gets plenty of oxygen from a proper potting mix. Most commercial blends are suitable for usage. Bromeliads, orchids, and African violets are just a few of the plants that demand certain mixes. You can either buy these blends or make your own. The formulas shown below can be used to create a homemade potting mix.
Growing Mix for Flowering House Plants
For the majority of gardeners, the following potting mixture will produce suitable flowering plants in most homes:
- 1 part potting soil or garden loam
- one part perlite, vermiculite, or sand
- portion peat moss
To 4 gallons of potting mix, add 2 to 3 ounces of 20 percent superphosphate and 3/4 ounce (by weight) of either bonemeal or dolomitic limestone. Add 3 tablespoons of a 6-6-6 or another equally balanced fertilizer to every 4 gallons (1/2 bushel) of mix after disinfecting the soil (see “How to Sterilize Soil”). In accordance with the manufacturer’s guidelines, add a minor element formulation.
Growing Mixes for Foliage Plants
Although the majority of foliage plants will thrive in the growing medium suggested for blooming house plants, they will thrive even more if the medium has a larger content of organic matter.
- 2 parts peat moss or 1 part sand
- Pine bark, one part
- 2 components peatmoss
- sand, one portion
4 gallons (or half a bushel) of mix should have 2 to 3 ounces (dry weight) of dolomitic limestone added. Set the pH for fluoride-sensitive plants no lower than pH 6.5. Fluoride levels in superphosphate are high enough to burn the leaves of delicate plants. To each 1/2 bushel of soil after sterilizing it, add 3 tablespoons of a 6-6-6 fertilizer or another fertilizer, such as 5-10-5. Fertilizers with plastic coatings can also be utilized; the majority call for 2 ounces per 1/2 bushel. In accordance with the manufacturer’s advice, mix in a minor element formulation.
Growing Mixes for Bromeliads
In Central and South America, bromeliads are either epiphytic (growing on tree branches or in tree crotches) or terrestrial plants (they grow in the ground). Although the majority of bromeliads can be grown successfully in soil mixtures for foliage plants, most thrive in specifically formulated soil mixtures. Any bromeliad mix needs to be well drained and aerated.
- 2 components peat moss
- Perlite, one part
- fir bark, one portion
- peat, one portion
- 1 part shavings of cypress
To 4 gallons (1/2 bushel) of soil mixture and a minor element mix, add 2 ounces of dolomitic limestone. 1 ounce of water-soluble fertilizer 10-10-10 should be dissolved in 3 gallons of water. When repotting plants and once a month when watering, use this solution. Add water until the vase-shaped formation created by the overlapping leaf bases is full.
Growing Mixes for Orchids
Because they both grow as terrestrial plants and as epiphytes on trees, orchids and bromeliads have a lot in common. Excellent aeration and drainage are essential in an orchid mix. Useful soil mixtures include the following:
- Osmunda tree fern fiber, 3 pieces (moisten before use by soaking in water for 12 hours)
- Redwood bark, one part
- 5 parts bark of fir
Epiphytic orchids can also be grown on tree fern slabs. For each 4 gallons (or half a bushel) of soil mixture, add 1 ounce (dry weight) of dolomitic limestone. Don’t mix in any fertilizer. Add 1/4 ounce of liquid 10-10-10 with minor components per gallon of water once the plants are potted, and fertilize once every six weeks (if the plants are growing in osmunda fern fibers). Use a liquid 30-10-10 fertilizer with minor components every six weeks rather than a 10-10-10 fertilizer if plants are growing in fir bark.
Growing Mix for Succulents and Cacti
- 2 parts potting soil or garden loam
- sand, two portions
- Peat: two portions
- Perlite, one part (crushed charcoal can be substituted)
To 4 gallons (1/2 bushel) of soil mix, 2 ounces (by weight) of bonemeal, and 1/2 ounce (by weight) of superphosphate, add 2 ounces (dry weight) of dolomitic limestone. Add a minor element supplement once the soil has been sterilized, as directed by the manufacturer.
Growing Mix for Ferns
Ferns thrive in the majority of suggested mixtures that have a high percentage of organic matter together with favorable soil drainage and aeration qualities. Use any of the listed plant combinations for foliage. However, the majority of ferns cultivated indoors thrive in the mixture shown below:
1 component fine sand
For every 1/2 bushel (4 gallons) of soil mix and 1/2 ounce of either bonemeal or 20 percent superphosphate, add 2 ounces (dry weight) of dolomitic limestone. Add minor components to the soil mixture after pasteurization. For every half bushel of soil mixture, add 1 tablespoon of a 6-6-6 or other similarly balanced fertilizer.