How to Grow Spinach Indoors
Updated: Jul 30, 2022
It’s funny to think about feeding our food, but it’s actually an important consideration when growing in a container.
It’s especially important when learning how to grow spinach indoors as it’s a controlled environment that’s fully dependant on what you add to fuel your young plants growth.
Other things I’ll walk through today for your indoor growing adventure are:
Seeds – selecting and starting
The best type of containers
Fertilizing spinach plants (aka feeding)
Harvesting and storing Spinach
Although most varieties work well, Baby’s Leaf Hybrid and Melody varieties grow especially well in containers.
Baby’s Leaf Hybrid Spinach Variety:
the leaves of this plant are a little tiny bit sweet which makes it awesome in smoothies. And it’s fantastic for growing indoors where you see it all the time because it matures ultra fast! 30 – 40 days from seed to salad. Plus, it tends to be more leaf than stem so really maximizes your containers space.
Melody Spinach Variety:
Is actually extremely similar to the Baby’s Leaf so you really can’t go wrong with either of these.
Starting spinach seeds
As Spinach plants tend to go into shock easily when transplanted and often halt growth for about a week once moved, it’s best to directly sow spinach seeds right into their permanent home. Another reason that spinach doesn’t transplant well is that it has a long tap root, and that’s always a recipe for discomfort when it comes to transplanting any crop.
Before planting, take the time to soak spinach seeds in water overnight – this will soften the seed coats and speed up germination. Just try not to leave them in water much longer than that or they’ll start to rot. 24 hours is the sweet spot.
Once ready, sow your seeds a half-inch (0.75cm) deep, spaced 1 inch (2.5cm) apart from each other and at least 2 inches from the side of your container.
One of the reasons that Spinach is fantastic at growing indoors is that their ideal soil temperature is around room temperature or a little cooler (depending on your home). They’re usually happies with rich soil that’s between 5-20°C (45-70°F). Give it about 5-10 days for your seeds to germinate. If you don’t see a seeding in 10 days, there’s a good chance that it’s not taking. One thing to consider is that Spinach seeds don’t store well, so, if possible, buy fresh seeds every year.
Caring for spinach grown indoors
Although Spinach can handle lower levels of sunlight than many other crops, what it can’t handle is poor soil. Spinach plants need good drainage, and loose fertile soil that’s high in rich organic matter. Because they need lots of water, but don’t do well being left to sit in water, it’s important that your container offers lots of drainage holes, and that you – yes you – offer your little green plant lots of consistent moisture.
Spinach plants like soil that’s slightly alkaline and can be slightly sensitive to acid soils. Therefore you’ll want to aim for a soil pH that’s between 6.5 -7.5.
Properly spacing spinach plants
Overcrowding spinach plants stunts their growth and encourages them to do what’s called bolting. Bolting is when your plant premature starts producing flowers to go to seed. Since this then also turns the spinach leaves quite bitter, that means that your little green crop is no longer going to be enjoyable to eat, so let’s avoid that!
By the way, bolting also tends to happen if the air or soil temperature gets too hot, or if the plant encounters what it feels is a drought – meaning it hasn’t been watered it regularly. Just FYI.
To avoid crowding, the rule of thumb is to thin your seedlings to ensure they have 4-6 inches (10-15cm) of space between them and least two true leaves.
But rules of thumbs don’t always account for lunch, and I feel that’s equally important. 😉
For this reason, what I personally do is plant my spinach about 2 inches apart from each other, and then when the plants have 2 true leaves and 2 regular leaves, I thin them down to 4 inches apart so that I can eat the seedlings I just thinned. Chop the roots and toss them into a smoothie or whatever makes you happy.
Then I wait until the remaining plants have 2 true leaves and 4 regular leaves, and then I thin them again so that the remaining plants are 6 inches apart. The thinned plants are then big enough to add to your plate rather than the compost, the remaining plants get the space they need to grow big and strong, and their root systems are still small enough to thin without damaging the remaining plants.
Try not to wait longer than that though as it could start getting complicated and harmful for the remaining plant roots.
Top 4 things to consider when you grow spinach indoors
Spinach is a quick-growing, shallow-rooted crop that isn’t tolerant of water stress. You’ll want to maintain enough moisture by frequently watering when needed.
Avoid watering practices that splash soil onto the leaves or otherwise damages them. The leaves like to be dry if possible, especially if they’re getting hit with direct sunlight
Ensure you have good drainage, their roots don’t do well sitting in water.
For best results water the same amount daily. I usually just evenly pour a cut of water throughout the container each morning and then re-use the water that drains out to water other plants in the home. Let’s just say that my palm tree LOVES that I grow spinach near by. 😊
Fertilizing Spinach Plants
Spinach is a heavy feeder and needs rich soil to thrive. Mix in a 1-2 tbsps of a complete organic fertilizer into every foot of soil before you plant your spinach and use a compost tea once every month or two. Spinach only grows for a total of about 3-4 months. So think of it as food to start, and a snack mid growth cycle.
For best results, I like to use either compost tea, fish emulsion, or cottonseed meal once your plants have about four true leaves. Compost tea is usually my first choice. But don’t let the name fool you as it’s not the kind of tea you’ll be wanting to curl up by a fire with. 😊 Unlike the tea you’re used to, compost tea is water that’s been steeped with compost, which then leaches some of its nutrients into the liquid.
Easy peasy, right?! The payoff is huge though – because the better your spinach plants are nourished, the better they’ll grow and then nourish you in return.
Containers for growing spinach indoors
Spinach does amazingly well in a container, just keep in mind you’ll want to allow one plant for each 8-inch pot, but a 10-inch-wide pot is just enough room to fit 2 plants in. This is based on surface space, but it’s also important to keep in mind that spinach plants have a deep taproot, so for best results, loosen the soil at least 1 foot deep before you plant your spinach seeds.
Potential Diseases when Growing Spinach indoors
Damping-off & Root Rot
These diseases will usually cause poor seed germination the disappointing death of newly emerged seedlings. Older plants tend to just wilt and collapse.
Improve your changes of avoiding it by plant your spinach in well-draining soils, while carefully managing watering to avoid soaking the soil.
When possible, use seeds that have been treated with fungicide, and avoid planting spinach successively in the same spot.
At first, yellow spots tend to appear on the spinach leaves which then become larger over time – turning a tan color with a dry texture. Purple fungal growth is usually found on the undersides of leaves, and severe infestations can cause curled and distorted leaves.
To avoid Downy Mildew, I usually just try to either be really mindful of my watering practices, or if it's a busy period in life, I make sure to plant disease-resistant spinach varieties when possible.
There are also preventative fungicides that you can use; however, I haven’t tried them since the ingredient list looks scary to me knowing that the entire leaf will eventually be in my belly. But that’s just me. Your local garden center can point you to the right product on the shelf if you’d like to try it. 😊
Yellow spots appear on the upper sides of leaves while clusters of white, blister-like pustules (pimple-like growths) appear on their undersides. Infected plants can collapse if the disease spreads fast enough.
In this case, crop rotation and ample spacing is what's needed. One of the biggest mistakes I see indoor gardeners doing is trying to fit too many plants in one container.
Like people, plants need space to let stretch and settle their roots. No one wants to be cramped in a small space with many all the time, and that includes your plants. You’ll usually harvest a lot more from fewer healthy plants than from many unhappy ones.
Harvesting Spinach Leaves
Within 6-8 weeks, you can start harvesting from any plant with leaves that are at least six 3-4 inches long. If you want your plants to keep producing, harvest by pinching off the outer leaves once they’re big enough to use.
You’ll want to avoid harvesting more than 50% of the leaves from a single plant. But, if you want to harvest the entire plant, simply cut it at its base and remove the older leaves.
For regrowth, leave about an inch below the leaves before clipping off the stems.
Store your spinach in its ideal conditions – a temperature around 32°F, with 95-100% relative humidity.
Spinach is very perishable, so it can only be stored for about 10-14 days.
Storage temperature should be as close to 32°F as possible, since your spinach will deteriorate faster at higher temperatures.