Why Do Plants Need Sunlight?

Understanding the crucial role of plant sunlight is essential for any plant enthusiast, whether you’re tending to a lush indoor jungle or a vibrant outdoor garden.

Two things are crucial to plant health: water and plant sunlight. Plant sunlight powers photosynthesis, the process plants use to synthesize food. More specifically, photosynthesis is how plants make glucose, combining carbon dioxide and water. When caring for plants, indoors or outside, it’s critical to know how much water they need as well as the proper amount of plant sunlight.

Just how much plant sunlight a plant needs depends on the plant species. Plants can’t talk, but they sure know how to communicate. It’s all visual with them, like when they’re not getting enough light. This guide will help you recognize the tell-tale signs of insufficient light and provide actionable strategies to ensure your green companions get the proper amount of plant sunlight to thrive.

How to Tell If Your Plant Needs More Sunlight

It’s Leggy

According to Patch Plants, “A leggy plant is one that’s got a lot more stem than leaf… If a plant has become ‘leggy’ it usually means it’s growing so that it has really long stems, with just a few leaves on the top. As plants grow they look for light. If they’re in a spot that’s bright enough for them they’ll be getting all the light they need and will grow normally. If they’re living in too little light they’ll start hunting for more.” Whether it’s a houseplant or an outdoor plant, stems that seem longer with fewer leaves are signaling they need more plant sunlight.

It Leans

Is your indoor or outdoor plant growing to one side or another, instead of straight up? That’s a red flag. When a plant leans toward a light source, it’s phototropism in action, trying to maximize its exposure to the plant sunlight it needs to survive.

Its Leaves Are Different

Changes in size and color can signal a critical plant sunlight shortage. For indoor and outdoor plants, watch for leaves getting smaller or looking pale. Another sign that your plant may need more plant sunlight: That beautiful variegation in the plant’s leaves that caught your eye at the nursery is fading or has disappeared. Shrubs, such as variegated dogwood, need sufficient plant sunlight for the green and cream-colored mottling to develop and maintain its vibrancy in the leaves.

It’s Not Flowering

Some indoor plants are forced to bloom by growers, and you can have a challenging time getting them to re-bloom. But an outdoor blooming plant like a flowering shrub? It should be flowering each year. If a potentilla isn’t flowering, or if it’s only producing a few flowers, lack of plant sunlight could be the culprit.

How to Provide More Plant Sunlight

Follow the Guidelines

Indoor and outdoor plants are always sold with recommendations for how much plant sunlight they need. Does the plant tag suggest north, south, east or west exposure? An indoor plant requiring low light might do well by a north-facing window. A perennial that needs lots of direct sunlight will do best facing southern or western sun. If you ignore the guidelines, there’s a good chance the plant won’t grow as it should.

Move Them Closer

If your indoor plants seem to be in a room where they should get enough plant sunlight, but they’re still suffering, move them closer to the window or light source. No place to set them? Hang them from the ceiling with plant hangers or elevate them with plant stands. Another option: Provide artificial lighting. (The University of Missouri has some great info on artificially lighting indoor houseplants.) Full-spectrum lights are sold in a range of configurations, from the classic style of long tube lighting to contemporary lamps.

Follow the Sun

Sometimes you have to chase the sun during the day so that your plants get enough plant sunlight, whether they’re indoors or outdoors on a sometimes-shady patio. To make them easier to move, put houseplants or patio plants in baskets with handles or on wheeled platforms. Then you can easily shift them around from sunny spot to sunny spot daily. Or move them every few days to give them more exposure to plant sunlight.

Dig It Up and Relocate

For perennials, Gardening Know How advises, “One rule of thumb is to transplant fall-blooming perennials in spring and spring flowering perennials in fall.” They also emphasize, “You should never move perennials when they are in flower. Wait at least a few weeks after a plant flowers to pick up the shovel.”

Also, if there is a forsythia at the corner of your house that isn’t producing the springtime burst of yellow blooms that it should, accept that it’s in the wrong location, grab a shovel and move it. Transplanting is sometimes the only way to ensure a plant gets the plant sunlight it needs.

FAQ

Can artificial light fully replace plant sunlight for plants?

While natural plant sunlight is the ideal and most complete source of light for plants, high-quality full-spectrum artificial grow lights can serve as an effective supplement or even a replacement in many situations, especially for indoor plants. The lights copy the sun’s spectrum; they offer wavelengths plants need for photosynthesis. But a person must manage the intensity and duration of the artificial light. This light needs to match a plant’s specific needs. Some plants, especially those that need high light or certain UV wavelengths from natural sun, do not grow to their full potential under artificial light. They do not compare to plants that grow outside in optimal natural conditions. It’s often a combination of available natural plant sunlight and supplemental artificial light that works best for many indoor environments.

How can I know what kind of sunlight a spot in my home or garden gets?

Observing the area throughout the day is the simplest method. Note when direct plant sunlight hits the spot and for how long. For a more precise reading, you can use a sun calculator app or a physical sun Zzard/meter. These tools can help you map out how many hours of direct, partial, or indirect plant sunlight specific locations receive. For gardens, also consider seasonal changes; a spot that’s sunny in summer might be shadier in winter as the sun’s angle changes.

Remember to differentiate between:

Full Sun: At least 6 hours of direct plant sunlight per day.

Partial Sun/Partial Shade: About 3-6 hours of direct plant sunlight, preferably in the cooler morning or late afternoon.

Full Shade: Less than 3 hours of direct plant sunlight per day, or filtered plant sunlight for most of the day.

About the Experts

Patch Plants is an online plant store and resource that helps people select, care for, and enjoy plants in their homes. They have a large assortment of houseplants and offer significant practical information and inspiration to plant parents of all levels.

Gardening Know How is a comprehensive online platform that offers gardeners a plethora of knowledge, how-to articles, and solutions to a wide range of gardening-related issues. Their goal is to assist people learn more about gardening and empower them to grow healthy gardens.