Grow Light for Lupine Seedlings: Light Distance Plus Hours
A grow light for lupine seedlings gives these sun loving plants a good start a windowsill cannot. University of Minnesota Extension advises lights no more than 4 inches above seedlings, with 2 inches ideal, for 12 to 16 hours daily. Scarify the seed first plus sow one seedling per cell.
The short answer
Hang fluorescent or LED lights 2 to 4 inches above lupine seedlings plus run them 12 to 16 hours a day, as University of Minnesota Extension advises for indoor starts. NC State Extension notes that scarifying lupine seed helps improve germination. Sow in divided cells so roots do not tangle before transplanting.
Why do lupine seedlings need a grow light?
NC State Extension notes that lupine species tend to do well in full sun. Indoor seedlings need light near full sun.
University of Minnesota Extension explains that a windowsill is not a good location for starting seeds. Spring sunlight is relatively weak compared to artificial light sources placed close to the plants.
University of Maryland Extension adds that seedlings in window light usually stretch and lean toward the light. They fail to form sturdy plants.
How close should lights hang?
University of Minnesota Extension advises lights no more than 4 inches above the tops of seedlings. As close as 2 inches is ideal.
Plants need 12 to 16 hours of light daily, the same source notes. Standard fixtures with two cool white fluorescent tubes give adequate light at low cost.
University of Maryland Extension notes that full spectrum grow lights produce thicker stems than cool white tubes. Incandescent bulbs give off more heat plus less light and will not produce good transplants by themselves.
| Setting | Guideline | Source note |
|---|---|---|
| Light height | 2 to 4 inches above seedlings | 2 inches is ideal |
| Light hours | 12 to 16 hours daily | Use a timer |
| Lamp type | Fluorescent or LED | Better than window light |
| Container | One seedling per cell | Roots do not tangle |
Source: University of Minnesota Extension plus University of Maryland Extension.
Why scarify lupine seed?
NC State Extension notes that scarification of sundial lupine seeds helps improve germination.
The same source lists root cuttings or seeds for propagation. For the wider genus, NC State Extension suggests planting seeds in the fall when sowing outdoors.
University of Minnesota Extension gives a rule of thumb of planting a seed two times as deep as its width when unsure of depth.
How to: step by step
- Scarify lupine seed to help germination.
- Sow into divided cells, one seedling per cell.
- Plant seed about two times as deep as its width.
- Hang lights 2 to 4 inches above the seedlings.
- Run lights 12 to 16 hours daily on a timer.
- Move seedlings into containers 1 to 2 inches wider once they outgrow their cells.
Troubleshooting
Seeds not sprouting: seed not scarified. Scarify before sowing.
Stretched stems: lights too high or too weak. Lower them to 2 to 4 inches.
Roots tangled at transplant: shared containers. Use one seedling per cell.
For related reading see cannabis seedling light schedule, leggy cannabis seedlings plus potting up cannabis seedlings. Kind Seed Co also stocks cannabis seeds.
Sources
- Lupinus (lupine), NC State Extension Gardener Plant Toolbox
- Lupinus perennis (sundial lupine), NC State Extension Gardener Plant Toolbox
- Grow lights for starting seeds indoors, University of Maryland Extension
- Starting seeds indoors, UMN Extension
FAQ
How many hours of light do lupine seedlings need?
University of Minnesota Extension notes that seedlings need 12 to 16 hours of light daily. A timer makes this easy to hold steady.
Can lupines be direct sown instead?
Yes. NC State Extension suggests planting lupine seeds in the fall for outdoor sowing. Sundial lupine also spreads by short rhizomes plus seeds and can be propagated by root cuttings. An indoor start under lights gives more control over early growth.
Do lupines bloom the first year?
NC State Extension lists lupines as annual, biennial or perennial depending on the species. Many bloom from late spring into early summer, and sundial lupine flowers last about a month. Timing of first bloom depends on the type grown, so check the seed packet.
Why do lupine seedlings stretch?
University of Maryland Extension notes that seedlings grown in window light usually stretch plus lean toward the light. University of Minnesota Extension advises lights no more than 4 inches above seedlings, with 2 inches ideal. Lowering the lamp is the first fix for stretched stems.
When should lupine seedlings be potted up?
University of Minnesota Extension advises moving seedlings that outgrow cell packs into containers 1 to 2 inches wider in diameter. Single seedlings per cell avoid roots growing into each other, which the source notes can lead to injury during transplanting. Harden plants off before planting outside.
