What Do Plants Need to Grow?

What do plants need to grow? Plants are a great addition to any home, whether indoors or outdoors, the benefits of adding some nature to your living space have been well documented. However, keeping plants alive and growing might be a daunting endeavor for some, especially those new to gardening. For the uninitiated, there are several factors that contribute to plant growth and different species have varying needs.

Here we take a closer look at some key elements from the amount of water, temperature and what kind of light plants need.

What Do Plants Need to Survive?

Speaking to Newsweek, Dr. Mary Williams from the American Society of Plant Biologists (ASPB) said: "Houseplants are wonderful companions but they depend on you to ensure that they are able to get the sunlight, minerals and water that they need to survive."

The American Horticultural Society says heat, cold and elevation are just a few of the variables that can have a big impact on plant growth and influence which plants will thrive in a given location.

Plant Species

Speaking to Newsweek, Rachel Jabaily, the director at large for education at the Botanical Society of America (BSA) and assistant professor of organismal biology & ecology at Colorado College, said: "It helps to know a bit about where your plant originated and evolved in order to keep it happy."

There are hundreds of thousands of plant species on Earth, with different species adapted to every environment, she added.

All plants require the same fundamental elements for survival (light, water, air and soil) and grow by the process of photosynthesis. But how much and what type of each element is needed depends on the plant you're trying to grow.

Plants on a shelf.
Different potted plants seen on a shelf. Bogdan Kurylo via iStock / Getty Images Plus

Jabaily explained: "Your home or office environment, indoors or outdoors, might be quite different than what the plant might need so be prepared to supplement with additional light, humidity, soil nutrients, or heat if you want your plants to thrive.

"For example, if you are trying to grow succulent plants, these will require high light, well-drained soil, and less moisture than many houseplants that are adapted to the understory of tropical rainforests," Jabaily told Newsweek.

What contributes to plant growth can "vary, often wildly, depending on the specific species" of the plant, David Bryant, a campaigns and engagement manager at the California Native Plant Society (CNPS), told Newsweek.

Bryant explained: "In California alone, we have upwards of 6,000 taxa of native plants, growing in a diversity of habitats from the desert to alpine peaks. Across these places, plants can require significantly different amounts of light, temperature, nutrients, soil and water to grow properly."

A woman looking after houseplants.
A woman looking after different houseplants on a wall. PIKSEL via iStock / Getty Images Plus

What Kind of Light Do Plants Need?

According to an article by Bodie V. Pennisi, a professor at the University of Georgia Cooperative Extension, light is the most important factor when it comes to growing plants indoors. This is because light is required to produce food and ultimately survive. So generally, the more light there is, the more food will be produced for growth.

Pennisi explains the amount of light in any given spot inside a home varies depending on the presence of trees outdoors and roof overhang (both of which may provide shade at certain times), reflectance from the wall color, window curtains, the amount of daylight hours as well as the time of day and year.

Growing plants in the U.S. can be particularly challenging because of the country's location in the northern hemisphere, according to the professor.

Windows with northern exposure to the sun provide the least amount of light. Those with eastern exposure generally provide the best light for indoor plants, as they receive direct morning light from sunrise until nearly midday. Windows that have southern exposure provide the largest range of light and temperature conditions, Pennisi says.

Sunlight over several plants by a window.
Sunlight over several plants by a window. OlgaMiltsova via iStock / Getty Images Plus

Among the four exposure locations, the northern exposure receives the least light and heat year round, she explains.

"Although most plants grown indoors will not grow in a northern room, they may tolerate it for short periods of time,"

The National Gardening Association (NGA) says: "Every plant has a preference for a certain exposure to sunshine. If you put a shade lover such as a hosta [a genus of plants] in full sunshine, it will die in no time at all. The opposite is true for sun lovers—if you put them in the shade, they won't live very long."

Plants usually come with a label outlining its light requirements. If a plant label says "high light" (meaning it requires a high level of light) but you were planning to put the plant in a spot that doesn't have adequate light, artificial light sources (such as fluorescent and/or special incandescent lights) can be used to supplement the natural light. Pennisi says.

The amount of light in a room is also affected by the season. "For example, the summer sun reaches a higher zenith compared to the winter sun. Therefore, sunlight penetrates farther into a room during winter," and the low winter sun shines across the room for most of the daylight hours."

How to tell if your plant is not getting enough light

The BSA's Jabaily told Newsweek: "Pay attention to visual cues from your plant that something isn't right—drooping, buds dropping, leaves changing colors."

Below are some signs that indicate a plant is not receiving sufficient light, as outlined by Pennisi:

  • The plant stops growing.
  • The spaces between the leaves (known as internodes) on the new growth are much longer than those on the older part of the plant.
  • The new leaves are smaller than the older leaves.
  • The leaf color is a lighter green on the newer foliage than on the older foliage.
  • The older leaves are dead.

Temperature

After light, temperature is the second-most crucial factor for plant growth. Most indoor plants can tolerate and thrive in temperatures ranging from 58 to 86 degrees Fahrenheit because most indoor plants originate from tropical and subtropical areas, according to Pennisi.

Temperature and light go hand-in-hand and can be thought of as the "yin and yang" of plant life, forming two parts of a circle, Professor Pennisi says. The two elements are connected by the processes of photosynthesis (a series of chemical reactions) and respiration.

The sugars and starch built by photosynthesis are broken down by respiration to provide energy for the plant's development of new tissues (which signifies growth) and for the maintenance of existing tissues. High temperatures expedite the respiration process.

Pennisi continues: "If the plant is not producing sufficient sugars (as under low light), then high temperatures may break down what little sugars are made, leaving little to none for growth.

"Maintenance takes precedence over growth; therefore, under insufficient light, plants do not grow. If light is so low that sugars produced are insufficient for maintenance, the plant eventually dies," she adds.

Sunlight shining through a room with plants.
Sunlight shining through a room with several plants. LookAod via iStock / Getty Images Plus

Why Do Plants Need Nutrients and Soil?

The ASPB's Williams explained plants get their energy directly from the sun, which they use to produce sugars from carbon dioxide. This process occurs through photosynthesis, which literally means "making things from light," she said. These sugars are used as energy sources by plants.

"Plants are amazing chemists that make their own vitamins. And of course, we get most of our vitamins by eating the vitamin-producing plants," Williams said.

To produce vitamins, plants need minerals, which are also used to produce their DNA, cell walls, and everything else, Williams said.

Plants get their minerals from the soil, so "it's important to replenish the minerals in the soil of your houseplants. Liquid plant foods are a great source, but you can also repot them into fresh soil from time to time," Williams told Newsweek.

Professor Pennisi says when repotting your plants, the new soil should be well-drained and aerated. Growers should be sure the new mix holds water and nutrients well and is within the right pH range (5.0-6.5), she adds.

Plant growers should also take precaution when adding fertilizer to plants.

Pennisi warns: "Danger from over-fertilization occurs because any fertilizer used, whether in liquid, powder, or tablet form, will dissolve in soil water and will form salts in the water. When you over-fertilize, the water in the soil becomes so salty that it 'burns' the plant's roots by removing water from them.

"The secret to fertilizing plants indoors is to apply small amounts of fertilizer as the plant grows. Without new growth, the plant has a limited need for more fertilizer."

Houseplants seen on a balcony.
Several plants in pots pictured on a balcony. loonara via iStock / Getty Images Plus

Water

The ASPB's Williams said plants need to be given "just the right amount of water."

"Too much and the roots literally drown in the soil, and too little and the plant wilts and eventually dies. Trial and error is the best approach to watering, but be aware that the plant's needs change seasonally," she told Newsweek.

Professor Pennisi says giving a plant too much water can suffocate its roots, while too little water could cause growth to become erratic and stunted.

How Much Water Do Plants Need?

The amount of water to apply and the frequency of watering plants depends on the following factors, according to Pennisi:

  • Plant type: Different plants have varying moisture requirements.
  • Soil moisture: Watering frequency is also dependent on the amount of water already present in the soil.
  • Plant size: Large plants need more water than smaller ones.
  • Volume of growing container: You may be required to water your plant more frequently if its growing container is quite small. Containers with saucers may cause a build-up of soluble salts, which can damage plant roots and lead to a decline in growth.
  • Light intensity: Plants under high light may require more watering as they transpire more water compared with plants under low light.
Plants by a window.
Plants by a window being watered. ronstik via iStock / Getty Images Plus