How to Grow Spinach in a Window Box

Do you want to experiment with growing veggies indoors in winter? We tried to grow spinach in a window box in the dead of winter.

If you have always wanted to try growing edibles indoors, spinach is the ideal crop to experiment with during the winter months. Spinach is a cool season crop that grows well in containers.

A lot of the wacky things that go on here at ImaginAcres are experimental. We’re learning from every experience. This is what makes it fun. Even when things fail, it was exciting to try.

This time around we attempted to grow spinach in a window box in the dead of winter. This experiment was super fun, because it actually worked!

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Growing Spinach Indoors

We have a glorious sunroom on the second level of our house. It faces southward and has big old windows all the way around.

In the summer time I grow a lot of our potted edible plants in this sunroom. They love the bright light and lack of leaf eating insects.

In the winter this room gets plenty of light, but there is no insulation, so it is mighty chilly. Most of our plants move downstairs for the winter months.

In late autumn, I started wondering if I could grow cold weather crops in the sunroom and have fresh produce in winter. I grabbed an old window box from our shed and dumped some soil and compost inside. Tiny little spinach seeds were carefully poked into the soil. I moved it into the sunroom and waited.

Nothing happened.

The soil was a bit dry so I watered it and waited again. Still nothing. Then a light bulb went off. Literally! I realized I needed to warm the soil in order for the seeds to germinate. Our handy dandy heat lamp came to the rescue! I clipped it to the box, turned it on and waited once again. Victory!! After a few days, tiny little seedlings were popping up out of the soil.

I took care of the little babies for weeks, they grew and they grew. They were at baby spinach size in a few short weeks. Finally, they were ready to harvest. So, it’s official, you really can grow spinach in a window box!

Those of you who follow these posts know that we’ve had our fair share of garden failures so it’s nice to have something work out right once in a while.

How to Grow Spinach in a Window Box Indoors

Growing leafy green edibles indoors is very similar to growing houseplants. All they need is good quality soil, water, and sunlight.

What You’ll Need to Grow Spinach Indoors:

Window Box: Any size window box will do. Aim for at least 6-8 inches deep. You will need one with a tray to catch extra water.
Organic Potting Mix: Enough to fill the window box. Don’t use soil from your garden. It may introduce disease to your young seedling.
Organic Fertilizer: A granular, slow release fertilizer that you mix into the soil before planting is best, or you can water with fish emulsion to fertilize. Fish emulsion does have an unpleasant odor to it, but if your window box is in an area away from you living space, it may not matter.
Spinach Seeds: Varieties to consider include Renegade and Butterflay.
Heat Mat: Spinach seeds will germinate at a temperature between 40˚F to 75˚F, but will sprout quicker in warm soil. Use a heat mat until they sprout.
Sunny South Facing Window
Water as Needed: Fill a watering can and keep it handy to make watering easier.

Directions for Planting Spinach in a Container

Fill the window box with potting mix.
If using slow release fertilizer, follow the directions for the amount to use for your container. Add and mix to combine with the potting mix.
Pre-moisten the potting mix before sowing your seeds. Add warm water into the window box and let it drain. You will want the soil mix slightly damp, but not soaking wet.
Sow your spinach seeds. Go ahead and sow your seeds heavily and plant them about 2 inches apart. Push them slightly into the soil about 1/8-inch deep, cover, and mist with water.
Place the window box on a heat mat.
Check the window box every few days for germination, mist with water if the soil surface has dried out, and wait for seeds to emerge from the soil. Once the seeds sprout, remove the container from the heat mat and place in a sunny window.
Water when the soil feels dry at the surface. You want to keep the soil moist but not waterlogged.
Harvest baby spinach by snipping individual leaves from the outside of the plants. The center of the plant will continue to grow and produce more foliage.
As the spinach plants get crowded, thin them to about 6 inches apart by cutting the entire plant right below its crown. This will give the remaining plants room to grow larger.

When spring arrives, slowly adjust your spinach plants to outdoor temperatures and continue to grow outside.

Spinach is finished growing when the plant bolts, or sends up a seed stalk. Since spinach is a cool season crop, hot weather and increased daylight naturally triggers spinach to bolt. Pull the plants, compost them, and try growing something else.

I hope our experience will encourage you to try growing spinach indoors in containers.

Do you want to experiment with growing other edibles indoors? Check out this article at Grow a Good Life: How to Grow an Indoor Garden.