Spinach plants that thrive in cold conditions excel in cool spring and autumn gardens, yet they have a tendency to bolt during the heat of summer, and harsh winter conditions can be detrimental to their survival. However, cultivating spinach indoors in pots provides the opportunity to harvest fresh, homegrown spinach throughout the entire year.
Though spinach flourishes in outdoor cool climates, cultivating this crop indoors comes with numerous advantages. Indoor growth not only enables winter spinach cultivation but also serves as a preventive measure against pests and bolting.
Additionally, growing spinach on your windowsill facilitates easier harvesting. The process of growing spinach indoors closely resembles caring for an indoor herb garden, requiring the right mix of light, water, and a touch of fertilizer. This guide is designed to assist you in cultivating a thriving spinach crop in your kitchen, regardless of the season.
1. Choose the right containers.
Spinach plants are adaptable to confined spaces and do not require exceptionally deep soil, but it is advisable to select pots with a minimum diameter of 14 inches. A pot of this size can accommodate around 3 or 4 spinach plants. While terracotta pots and planters are conventional options for indoor gardens, spinach can also be grown in grow bags. Ensure that the chosen container, whatever it may be, has ample drainage holes to avoid waterlogged soil.
2. Use a quality potting mix.
If you’re accustomed to cultivating spinach in an outdoor garden, the temptation to use garden soil in your indoor pots may arise, but it’s not advisable. Garden soil tends to have poor drainage when used in containers. Instead, opt for a nutrient-rich, well-draining potting mix for your spinach plants. You may also want to enhance it by incorporating a handful or two of compost or worm castings before commencing the planting process.
3. Pick a bright location.
While spinach doesn’t require as much bright light as certain other vegetables, it’s still necessary for successful indoor growth. Providing at least 4 to 6 hours of light daily is essential for robust growth and the production of lush leaves. To guarantee that spinach gets sufficient light, place your plants on a sunny windowsill or position them under a bright grow light.
4. Follow planting instructions.
Indoor spinach cultivation can begin with nursery-started plants, but starting from seeds is generally more straightforward. Seeds can be initiated at any point in the year, with the option to sow them successively every few weeks. To facilitate proper growth, plant spinach seeds at a depth of half an inch in holes spaced approximately 2 inches apart.
5. Use a heat mat.
Even though spinach thrives in cool weather, the germination of seeds may be hindered in excessively cold temperatures. This may not pose an issue if you are cultivating spinach indoors, but if you choose to grow it in a garage or another outbuilding, it could be beneficial to place a heat mat under your plant pots to expedite germination. Spinach seeds kept within the temperature range of 40 to 75°F should typically germinate in approximately 5 days.
6. Water regularly.
After planting your spinach seeds, it’s important to maintain regular watering to keep the soil consistently moist without becoming waterlogged. In the early stages when the seeds are young and delicate, using a mister bottle can be a gentle way to water the pots without dislodging lightweight seeds. As the spinach sprouts and grows, water the plants when the top inch of soil feels dry. Direct the water stream towards the soil line to ensure the spinach leaves remain dry, promoting a disease-free environment.
7. Thin out seedlings.
When spinach seedlings reach a height of a few inches and develop one or two sets of true leaves, it’s advisable to thin them out. The goal is to choose the healthiest plants and prevent overcrowding in pots, which can result in stunted growth and susceptibility to plant diseases. Thin out the spinach seedlings, leaving them spaced approximately 3 to 5 inches apart. Additionally, the seedlings you remove can be utilized as edible garnishes and microgreens.
8. Avoid excessive heat.
If you grow indoor spinach in winter, you won’t need to worry much about your plants getting too hot, although you’ll still want to keep your spinach away from space heaters. However, if you grow spinach indoors in summer, you may need to protect your plants from heat by moving them away from hot windows when temperatures climb. Remember, temperatures above 80°F cause spinach plants to bolt.
9. Apply fertilizer.
Indoor spinach needs less fertilizer than plants grown in the garden, but spinach crops will still produce more leaves if they’re grown in rich soil. Starting your spinach out in a quality potting mix that has been amended with compost is a good place to start, but you may still want to fertilize potted spinach plants throughout the growing season. For optimal growth, use a balanced, liquid organic fertilizer diluted to half strength and apply it once every 2 to 3 weeks from spring to fall.
10. Harvest frequently.
Indoor spinach is ready to harvest in about 35 to 45 days after planting. You can either harvest entire spinach plants all at once or you can clip away the oldest leaves towards the exterior of the plant and allow the younger leaves to continue to grow. Spinach will have the best flavor if you harvest leaves when they’re still tender, but the flavor of spinach begins to degrade when plants start flowering. If flowering occurs, pull up your spinach plants and sow new seeds to keep your indoor crop going strong.
