Kelvin temperature is used to describe the visual color of light that a lamp emits. Technically, it is a measure of how white a piece of tungsten steel is when it’s heated to a specific temperature in degrees Kelvin. A lamp with a Kelvin measurement of more than 5000 Kelvin (K) produces more light in the cool blue spectrum.

Lamps with a lower measurement, in the 3000K or lower range, produce more light in the warm red spectrum. Kelvin temperature is not a measurement of actual hotness or coolness of the lamp, but rather the visual temperature of light, which can have a big impact on how your indoor space looks.

Gardening Under Lights Book

In some cases, every place that a plant leaf is wounded is an opportunity for rooting. This begonia leaf below has been damaged, which caused it to develop tiny baby plantlets along the leaf vein.

Now, the leaf can be laid flat on the soil surface, and the little plantlets will begin to root.

Scale is a tough greenhouse pest,that is prone to attacking citrus. They are oval-shaped insects with either a hard or cottony shell, with different colors. They cluster on stems and base of leaves, and I have even seen them overwinter on pots.

To help control all pests and diseases, always keep your pots, seed trays, and tools clean. You can clean and sterilize reusable pots and trays with solutions of hydrogen peroxide, a 10 percent bleach solution, or diluted vinegar.

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Tomatoes are a warm-season crop that can grow at temperatures between 60°F and 80°F (15–26°C), but that doesn’t mean they will perform their finest at a constant temperature of 80°F (26°C). If you have tomato fruit on your plants but they just won’t ripen, temperatures are consistently either too cool or too hot.

Plants are adapted to cooler nights in their outdoor environment, so they will perform better with temperature changes that mimic their natural habitat.

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A good technique for most in-home growers is to start seedlings, cuttings, and young transplants using cool full-spectrum LED or cool full-spectrum high-output (HO T5) fluorescent lamps. 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.

This grow tent has two separate lighting sections; one with cool-blue light for vegetative plants, the other with warmer red light for flowering.

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Garlic needs a specific temperature and photoperiod combination to form harvestable bulbs, which makes it a bit trickier to grow indoors.

Garlic is not only photoperiodic, but it also requires vernalization to form bulbs. This is why you must plant garlic cloves in the fall, then harvest the following spring or summer. You may find garlic a tough crop to crack if you try to grow it indoors at consistent temperatures and photoperiods.

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Root plugs are typically made from hydrophilic, or water-absorbent, polyurethane foam. Biodegradable organic root plugs are also available.

Root plugs are often inoculated with beneficial microbes to help seeds and cuttings get off to a great start.

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Simple lamp timers, or more sophisticated digital timers, can be used to turn your grow lamps on and off on a set lighting schedule. Timers make it easy for you to deliver the right duration of light, or photoperiod, to your plants.

A quantitative short-day plant may bloom earlier or better if it has longer nights. A quantitative long-day plant may bloom earlier or better when given shorter nights. Both plants will eventually flower, however, even if the photoperiod is not ideal.

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