All of them. My LED Grow Lights are full spectrum, so you can use the same light for every stage of vegetable and fruit growth, from seedlings through vegging to flowering and fruiting. The dimmer switch lets you match the intensity to each stage.
The stages of vegetable and fruit growth
Plants grown for vegetables and fruit pass through a few clear stages, and each one asks something different of a light. Here is what happens at each stage and how the same light handles all of them.
Germination and seedlings
Seeds need warmth and moisture to sprout, but as soon as a seedling pushes up it needs light, or it will stretch and weaken. Young plants do not need intense light. A gentler setting on the dimmer, with the light held at a comfortable distance, is plenty, and a bluer light helps keep seedlings and cuttings short and strong. Seedlings usually do well on 14 to 16 hours a day. See starting seeds indoors with LED grow lights.
Vegetative growth (vegging)
In the vegetative stage plants build leaves, stems and roots, and they use more light as they get bigger. For leafy crops such as lettuce, spinach, kale and herbs, this stage is the whole life of the crop until harvest. For fruiting plants it is the stage when they build the structure that will later carry flowers and fruit. Growers raise the intensity gradually as the plants fill out; a common range for this stage is about 400 to 600 µmol/m²/s. Read what PPFD is.
Flowering, blooming and fruiting
Plants such as tomatoes, peppers, cucumbers, strawberries and citrus trees eventually switch from making leaves to making flowers and then fruit. This is the stage that asks the most of a light, because flowers and fruit take a lot of energy. Commonly quoted intensities run from about 600 to 900 µmol/m²/s. A redder light is traditionally used here, because red light is primarily known for boosting flowering and fruit production.
Ripening and harvest
As fruit ripens, plants still need good light to finish it. Keep the light steady, keep an eye on the leaves and harvest when the fruit is ready.
Why growers used to switch between MH and HPS lights
Traditional grow lights come in two main types. Metal Halide (MH) lights give off a bluer light, so growers used them for the vegging stage. High-Pressure Sodium (HPS) lights give off a yellow and red light, so growers used them for the flowering and blooming stage. That meant owning two kinds of light and swapping from one to the other partway through every crop.
The great thing about My LED Grow Lights is that the full spectrum of light means there is no need to worry about switching from MH for the vegging stage to HPS for the flowering and blooming stage. The LM301b/h LEDs are full spectrum with IR/UV LEDs, so you can use the same light for all stages of growth. Being full-spectrum white light, it also has a more natural color to the human eye than the blue of MH or the yellow and red of HPS, which makes it easier to check your plants for pests and disease at every stage. Read about full spectrum LED grow lights.
How to use the dimmer through the stages
The dimmer switch gives the indoor grower full control of the light intensity as needed. It is how one light does the job of several. As a starting point:
| Stage | Light setting | Hours of light |
|---|---|---|
| Seedlings and cuttings | Low intensity, light kept further away | 14 to 16 |
| Vegging | Raise gradually as plants grow | 14 to 16 for most crops |
| Flowering and fruiting | The highest intensity the plant can use | 12 to 16 for day-neutral crops |
Every plant is different, so watch yours and adjust. Plants that stretch, turn pale or grow weakly may need more light. Leaves that bleach, curl or scorch near the light may be getting too much, so dim the light or raise it. Make changes gradually rather than all at once.
Moving from one stage to the next
With MH and HPS lights the move from vegging to flowering meant changing lights. With a full-spectrum LED light, the move is simply a decision about intensity and timing. Move on when the plant tells you it is ready: a fruiting plant that has filled its space with healthy leaves and starts to show flower buds is ready for the higher intensity of the flowering and fruiting stage. A leafy crop never needs to move on at all. Raise the dimmer a little at a time, watch how the leaves respond for a few days, and then raise it again if the plant looks happy.
Day length matters too
Intensity is only half of the picture. The number of hours of light each day matters as well, and a timer makes it easy to get right. Seedlings, leafy greens and herbs are commonly grown under long days of around 14 to 16 hours. Tomatoes and peppers are day-neutral: they flower as they mature, not because the days get shorter. Some flowering plants, such as chrysanthemums and poinsettias, are short-day plants that need long, uninterrupted nights before they will flower. Read how many hours of light plants need.
Common mistakes at each stage
- Seedlings too close to a strong light. Young plants are delicate, so start low and keep your distance.
- Changing the intensity suddenly. Plants adjust best to small steps, not big jumps.
- Forgetting the timer. Plants thrive on a steady routine, so use a timer rather than the wall switch.
- Ignoring the leaves. They show you whether the light is too strong or too weak long before the plant suffers, and the natural color of full-spectrum white light makes them easy to read.
- Buying for the wrong stage. You do not need a different light for every stage. One full-spectrum light with a dimmer switch is enough.
Vegetables and fruit that suit LED growing
- Leafy crops: lettuce, spinach, kale and herbs. See growing herbs and leafy greens under LED lights.
- Fruiting crops: tomatoes, peppers, cucumbers and strawberries. See growing tomatoes and peppers under LED lights.
- Trees: citrus that must come indoors for winter. See growing citrus indoors under LED lights.
A sample schedule from seedling to harvest
Timing varies a great deal between crops and varieties, so treat this as a pattern, not a calendar. A fruiting plant such as a tomato might follow this path:
| Stage | Roughly how long | Dimmer and hours |
|---|---|---|
| Seedling | The first few weeks after sprouting | Low to moderate; 14 to 16 hours |
| Vegetative growth | Several weeks, until the plant fills its space | Raise in steps; 14 to 16 hours |
| Flowering and fruiting | Many weeks, until the fruit ripens | High; 14 to 16 hours |
A leafy crop such as lettuce skips the last row and is harvested a few weeks after sprouting. Check the seed packet for days to maturity, and plan your light around it.
Key takeaways
- A full-spectrum LED can be used at every stage of vegetable and fruit growth.
- Use the dimmer: low for seedlings, rising through vegging, highest for flowering and fruiting.
- Change intensity gradually and watch the leaves.
- Leafy crops never need the flowering stage; fruiting crops do.
- Day length matters as well as intensity; use a timer.
LED grow lights for hydroponic gardening
One of the best applications for using LED grow lights is in hydroponic gardening, which is well suited for indoor growing, where lights would be used. See LED grow lights for hydroponics for how to light a soil-free garden.
Back to growing with LED lights.
Related reading
- How Far to Hang LED Grow Lights From Plants
- Grow Tent Lighting Setup
- Back to Growing With LED Lights