Thermoperiods for Plants in Grow Tents

March 20, 2019

A crucial temperature measurement for your plants is the difference between day and night. This change is called the thermoperiod. Plants rest at night in cooler temperatures, when photosynthesis, respiration, and transpiration slow, and recover from stress and water loss. Cooler night temperatures can also increase flower size, keep flower color vivid, and extend flower life.

If your tomato plants keep flowering, but don’t set fruit, temperature are too hot.
PC: Leslie F. Halleck

If you’re growing plants in a tighter enclosed space, such as a small closet or a sealed grow tent, pay close attention to the heat output of your lamp. Many grow tents specify that, for example, you need to air-cool the tent when using a lamp that pulls more than 600 watts. Otherwise far too much heat will build up inside your tent.

Gardening Under Lights Book

Light Photoperiods for Growing Squash Indoors

March 19, 2019

If you want to grow squash indoors with grow lighting, you're in luck! Squash will flower under a variety of photoperiods, and you can grow them successfully with anywhere from 12 to 18 hours of light; 12 to 14 hours are adequate with high-intensity lighting.

PC: Leslie F. Halleck

You will have to hand-pollinate indoor squash flowers. Squash and other cucurbits produce male and female flowers on the same plant. Male flowers typically emerge first, followed by female flowers, which have a swollen ovary (looks like a mini fruit) behind the flower.

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

Countertop Grow Lights

March 18, 2019

Many countertop lamp setups allow you to grow small edibles, such as microgreens, small lettuce transplants, small herbs you keep snipped, and seedlings you plan to transplant outdoors. They typically take up only 2 to 3 square feet of space, and they may fit under your kitchen cabinets.

I installed these cool full spectrum grow lamps with small reflectors under cabinets to support small herbs and lower light houseplants.
PC: Leslie F. Halleck

Just remember that as plants grow and reach the lamp they may burn, so harvest herbs and transplant seedlings before they get too tall.

Gardening Under Lights Book

Use a Humidity Dome to Root Cuttings

March 17, 2019

Plant cuttings need slightly higher humidity as they develop new roots. Cover all cuttings with a humidity dome to keep moisture high during rooting. Don’t overcrowd: while you have to maintain humidity around the cuttings during rooting, they also need good air circulation.

An aeroponic propagator.
PC: Leslie F. Halleck

Site cuttings away from intense or high levels of light, which could burn them. Bright light from a window or a couple of feet away from fluorescent or CFL fixtures will be sufficient until the cuttings have rooted.

Gardening Under Lights Book

Some Seeds Need Red Light to Germinate

March 16, 2019

Some plant seeds do not germinate until they are exposed to red light. If you have ever tried to grow lettuce from seed, only to be disappointed when the seeds did not sprout, you most likely covered the seeds with soil and blocked them from the light.

Lettuce seeds require light to germinate.
PC: Leslie F. Halleck

Check the seed pack to see if your seeds need some exposure to light to germinate before you plant them.

Gardening Under Lights Book

Coir for Seed Starting

March 15, 2019

Coir is excellent for growing seedlings and mixing into the growing media for larger plants. You can use coir alone or in combination with other ingredients, or even as a hydroponic substrate.

PC: Sunlight Supply, Inc.

Coir also holds moisture well for an extended period while maintaining a porous structure that drains well. I like to sprinkle a little coir on top of the soil when I'm germinating seeds, as it helps hold just the right amount of moisture for seeds to germinate successfully.

Gardening Under Lights Book

Grow Dwarf Squash Indoors

March 14, 2019

Want to grow squash plants indoors? Standard squash plants are vines - and they can get BIG - reaching 15 to 20 feet long. Dwarf bush squash, on the other hand, will stay in the 3- to 5-foot range and are easy to keep in containers indoors.

PC: Leslie F. Halleck

It's always best to direct seed squash outdoors or into final container you plan to use indoors indoors. While many garden centers will offer transplants of squash plants and their relatives, these plants do not transplant well and growth is often stunted after transplanting.

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

Full-Spectrum Lamps Emit All Colors of Light

March 13, 2019

Full-spectrum grow lamps, whether they skew warm or cool, will emit some percentage of all colors of light within the PAR range. Cool full-spectrum lamps will still emit some red and yellow light, but less of it. Warm full-spectrum lamps will still emit some blue and green light, but less of it.

Seedlings growing under full-spectrum fluorescent lamps.
PC: Homestead Gardens

I can grow young tomato transplants in an open space under a large eight-lamp fluorescent fixture filled with cool-spectrum lamps. As plants grow, I replace half the cool-spectrum lamps with some warm-spectrum fluorescent tubes when I want to trigger more flowering.

Gardening Under Lights Book

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