Jiromaru Spinach

About This Plant

Jiromaru is a Japanese heirloom spinach prized for its thick, tender, and flavorful leaves. It thrives in cooler weather and is an excellent choice for spring and fall gardens.

This variety is well-suited for small spaces and containers, making it a great option for beginners who may not have a large garden plot.

Planting

Sow seeds directly outdoors in early spring as soon as the soil can be worked, or in late summer for a fall harvest. Plant seeds about half an inch deep and thin seedlings to 6-8 inches apart once they sprout.

Work compost or a balanced fertilizer into the soil before planting to give your spinach a strong start.

Watering Tips

Consistent moisture is key to producing tender, succulent leaves. Water regularly to keep the soil evenly moist, but avoid letting it become soggy. Mulching around the base of the plants helps retain moisture and suppress weeds.

Avoiding Bolting

Spinach bolts (goes to seed) when temperatures climb above 75°F. To extend your harvest, plant in a spot that gets afternoon shade during warmer months, and keep the soil consistently cool with mulch.

If you see a tall center stalk forming, harvest your remaining leaves right away — once bolting starts the leaves turn bitter quickly.

Common Issues

Watch for aphids, leaf miners, and slugs. These can be managed with insecticidal soap, neem oil, or hand-picking. Avoid overhead watering and ensure good air circulation to reduce the risk of downy mildew.

Growing in South Jersey (Zone 7a)

In the 08071 area, the average last spring frost is around April 15 and the first fall frost is around October 15, giving you a roughly 183-day growing season. Spinach is a cool-season crop, so you have two great planting windows here.

For a spring crop, direct-sow seeds outdoors as early as mid-March — spinach tolerates light frost and actually prefers cool soil. You should get several weeks of harvest before summer heat causes bolting in late May or June. For afternoon shade, the east side of a fence or taller crop works well in the South Jersey sun.

For a fall crop, sow again in late August to early September. The cooling temperatures into October and November are ideal for spinach, and light frosts will sweeten the leaves rather than harm them. With a simple row cover, you can often extend the harvest into December.