Grow Light for Sunflower Seedlings: Short Indoor Start
A grow light for sunflower seedlings gives these fast growers a short indoor start. University of Minnesota Extension notes that sunflowers can be direct seeded or germinated indoors plus planted once true leaves have formed. Use biodegradable pots plus move plants out young.
The short answer
University of Minnesota Extension notes that sunflower seeds germinate within 7 to 10 days plus can go into the garden once true leaves have formed. Sow indoors in biodegradable containers so the whole pot can be planted without disturbing roots. Use fluorescent grow lights rather than window light to limit stretching.
How long should sunflowers stay indoors?
University of Minnesota Extension notes that sunflower seed can be germinated indoors plus planted in the garden once true leaves have formed. So the indoor stage stays brief.
Seeds germinate within 7 to 10 days, the same source notes. UF IFAS Gardening Solutions adds that sunflowers grow rapidly.
NC State Extension describes the common sunflower as a warm season, fast growing annual. It also notes that the plant has a taproot.
Which lights suit sunflower seedlings?
University of Maryland Extension notes that the natural light from a window is seldom enough for good seedling growth. Seedlings on a sill usually stretch plus bend toward the light.
Sowing seeds under fluorescent lights is the easiest way to control growing conditions, the same source notes. Shop lights with two T8 tubes are inexpensive plus widely available.
University of Maryland Extension adds that full spectrum grow lights produce thicker stems than cool white tubes. Incandescent bulbs give off more heat plus less light.
| Step | Guideline | Source note |
|---|---|---|
| Container | Biodegradable pot | Plant the whole pot |
| Seed depth | One inch | Large seed |
| Sprouting | 7 to 10 days | Fast start |
| Plant out | Once true leaves form | After frost has passed |
Source: University of Minnesota Extension plus University of Maryland Extension.
What pots suit sunflowers?
University of Minnesota Extension advises sowing sunflower seeds indoors in biodegradable containers. This allows the entire pot to be planted without disturbing the seedling roots.
Plant seeds one inch deep, the same source advises. Once outside, sunflowers enjoy full sun.
University of Minnesota Extension suggests about 6 inches between varieties 2 to 5 feet tall. Space taller sunflowers at least 1 foot apart plus giant types 2 feet apart.
How to: step by step
- Sow seed one inch deep in biodegradable pots.
- Place pots beneath fluorescent grow lights.
- Expect sprouts within 7 to 10 days.
- Plant out once true leaves have formed.
- Plant the whole pot without disturbing the roots.
- Space plants according to mature height.
Troubleshooting
Leaning seedlings: window light only. Move under grow lights.
Root disturbance at transplant: plastic pots. Use biodegradable containers.
Weak tall stems later: wind exposure. Stake plus shelter tall varieties.
For related reading see cannabis seedling light schedule, leggy cannabis seedlings plus potting up cannabis seedlings. Kind Seed Co also stocks cannabis seeds.
Sources
- Sunflowers, University of Minnesota Extension
- Sunflowers, UF IFAS Gardening Solutions
- Helianthus annuus (sunflower), NC State Extension Gardener Plant Toolbox
- Grow lights for starting seeds indoors, University of Maryland Extension
FAQ
Is direct sowing better for sunflowers?
Either way works. University of Minnesota Extension notes that you can direct seed into the garden or germinate indoors, plus the cultivation is the same afterward. Direct seed sunflowers after all danger of frost has passed. An indoor start simply gives plants a short head start.
How fast do sunflower seeds sprout?
University of Minnesota Extension notes that sunflower seeds germinate within 7 to 10 days. The seed is large plus easily handled, which makes it one of the easiest flowers to start from seed. Plant seeds one inch deep, whether indoors in pots or directly in the garden.
How tall do sunflowers grow?
UF IFAS Gardening Solutions notes that most garden cultivars are 4 to 5 feet tall, though some types can grow to 12 feet. NC State Extension lists stems from 2 to 10 feet tall. Taller varieties may need a sheltered spot plus stakes to support the stems.
Can sunflowers bloom all season?
Yes. University of Minnesota Extension notes that sunflowers can be planted in succession for season long color. Sunflowers also come in colors from pale white to deep red, not just yellow, according to the same source. Seeds germinate within 7 to 10 days, so each new round comes up quickly.
What soil suits sunflowers?
NC State Extension notes that the common sunflower prefers full sun plus moist, well drained loamy, sandy or clay soils with a neutral or alkaline pH. The plant is easy to grow plus needs very little maintenance. It can be prone to powdery mildew, leaf spots plus rust.
