Depending on your climate and outdoor growing conditions through the seasons, you may have to start seeds of certain crops indoors a few weeks, or even months, ahead of outdoor planting days in order to harvest a successful crop. This is where an indoor seeding station comes in handy. You need only a few square feet of space to prepare a couple of seed trays with a small lighting setup.

Sowing new plants from seed is downright exciting. It’s also economical. Starting your own seeds is a very cost-effective way to grow a large quantity of plants quickly, plus you’ll be able to grow a much wider variety than if you buy only finished transplants from a garden center.

Gardening Under Lights Book

Much of the information provided online or by manufacturers for calculating your lighting needs is based on watts. While energy use is an important consideration, it is an input, not an output.

Without any additional sunlight, you can estimate that:

• A 1000-watt lamp lights a 36- to 40-square-foot growing space.

• A 600-watt lamp lights a 20- to 36-square-foot growing space.

• A 400-watt lamp lights a 12- to 16-square-foot growing space.

• A 250-watt lamp lights a 6- to 9-square-foot growing space.

• A 150-watt lamp lights a 3-square-foot growing space.

Gardening Under Lights Book

Small fluorescent grow lamps don’t generate as much heat as incandescent lamps, so you can situate them much closer to your plants, especially young seedlings, for better results.

In a fluorescent fixture that holds four to eight tubes, you can use a combination of lamps with different color spectrums. If you buy a T5 fixture that holds eight fluorescent tubes and is zoned with multiple on and off switches, you can turn on only your blue lamps during the vegetative phase and then switch on the red with the blue to initiate flowering.

Gardening Under Lights Book

If you are looking to boost flower production, HPS lamps traditionally outperform both MH and fluorescent lamps. In terms of total light output, an HPS lamp will provide about six times the light of an incandescent lamp.

Because HPS lamps produce a warmer spectrum of light, they are often used to trigger flowering in plant crops.

Gardening Under Lights Book

If you are growing just a few plants in a very small space, CFLs produce a good spectrum for cannabis and can be placed much closer to your plants than HID lamps. HO T5 fluorescents are also a good option. Both are best suited to growing plants during their vegetative phase, so you might consider supplementing with some red light during the flowering phase with warm-spectrum T5s or red LEDs.

HID LED rigs are good for both growth phases of cannabis. You will need to place HID LED fixtures a bit further away from your plants than you would CFLs or T5 fluorescents.

If you are growing larger groups of cannabis plants, you'll be better served by upgrading to HID lighting (Metal Halide, High-Pressure Sodium, CMH/LEC, or HID LEDs) for best results.

New BOOK! Gardening Under Lights: The Complete Guide for Indoor Growers

I use my quantum flux meter to make decisions about which lamps I’ll use to grow which plants, and at different stages of development.

Don’t confuse a quantum flux meter with standard visual light meters or Watt meters. Using a Watt meter and a standard light meter that measures lumens, you can calculate LPW outputs for a given lamp, which helps you assess efficiency.

You can also use standard light meters to measure footcandles of light. But remember that standard light meters, which measure in footcandles or lux, are not accurate for determining plant light needs.

Gardening Under Lights Book

If you’re growing fruiting crops, you can switch plants or lamps to a warmer spectrum (more red light) once you’ve bumped them up to larger pots to trigger stem elongation and flowering. If you need your plants to flower and they require a specific photoperiod to do so, they will require red light.

Cannabis will need close monitoring of lighting to trigger the plants into flowering.

Gardening Under Lights Book

CMH lamps offer a solid full-spectrum output, including some UV and far red light. They are available in two Kelvin measurements: 3100K and 4200K. The 3100K lamps are good for growing plants from vegetative to flowering to fruit without switching lamps, whereas 4200K lamps are best for propagation and vegetative growth.

Fruiting crops like cucumbers, squash, peppers, and tomatoes flower very well under a 315-watt 3100K LEC (Light Emitting Ceramic) lamp without any additional red-light sources.

Gardening Under Lights Book