Senposai is one of the most interesting hybrids to come out of Japan. It’s a cross between the Japanese mustard green (Brassica rapa) and cabbage (Brassica oleracea). The resulting cross looks like spinach, tastes like cabbage, but grows as well as mustard.

This delicious leafy green has only been around for a few decades, so don’t worry if you’ve never heard of it before.

We are going to tell you all about growing Senposai in your garden. You’ll love this fast-growing species that produces tasty greens packed with nutrition. And you will learn the best way to plant, grow, and harvest the unique and rare senposai plant.

Once you know how to grow and harvest senposai leaves, we will let you know some common ways to eat this fantastic healthy green.

What Is Senposai?

Senposai originates from Japan along with many other hybrid crosses of various brassica varieties. Senposai is often considered to be a subspecies of the Japanese mustard green Brassica rapa var. Perviridis, one of the two parent plants. The other parent is thought to be the ordinary cabbage, another Brassica species that is easy to cross.

The result is a leafy green plant that combines the mustard’s quick-growing nature and tender leaves with cabbage’s sweet and delicate flavor.

Where to Buy Senposai Seeds

Because senposai is a rare hybrid, you’ll rarely find it in the store. Even specialty stores rarely carry senposai greens, so your best bet is to grow it yourself. Gardeners wanting to grow senposai should find a reputable seed company online to purchase high-quality seeds free of diseases.

Senposai seeds are typically an F1 hybrid, meaning seeds from these plants may be sterile or produce unexpected and less desirable plants the following season.

What Does Senposai Taste Like?

Being a cross between mustard and cabbage, you’d expect the spiciness of the mustard to be the star. With senposai, the mustard lends little flavor. It instead lets the slightly sweet taste of cabbage shine through. The young leaves are tender and crisp, with a texture similar to spinach greens. Senposai is eaten raw in salads or cooked in stews, soups, and stir fry recipes.

How To Grow Senposai

Senposai follows many of the same practical considerations you’ll deal with when growing other Brassica varieties. Most regions will succeed in growing senposai in the spring and fall with a break in the hottest summer months.

Senposai is tolerant of frigid temperatures, with gardeners reporting crop survival to temperatures as low as 12 degrees Fahrenheit. It does not tolerate high heat well, so it’s best to plant and harvest senposai in spring and late summer.

1. Sprouting Senposai Seeds

Gardeners can sow seeds directly in the garden two weeks after the last frost, but you’ll have more success starting seeds indoors a week or two before the last frost.

Senposai is an astonishingly fast grower that will mature in 30 to 40 days. Gardeners want to start seeds to ensure they can grow plants before temperatures start to warm up to prevent bolting.

2. How To Plant Senposai in Your Garden

You should start your garden by preparing the soil for optimal growth. Senposai is a big nutrient consumer that will need well-draining and fertile soil, so mixing aged manure into your garden soil in the fall before planting is a must. This step gives you a perfect gardening bed that will ensure the rapid growth of senposai greens.

Gardeners planting senposai from seed should place seeds shallowly to a depth of about one-fourth of an inch. Plant seeds 6 inches apart in rows 18 inches apart. Once seedlings have three or four true leaves, you must thin to 12 inches to 18 inches.

The seedlings will be five to six weeks old when they are ready to transplant. It’s a great idea to use row cover when your seedlings start popping out to prevent pests and encourage fast growth.

This plant grows so fast that you can plant senposai a week or two apart to extend your growing and harvesting season. You can produce successive generations between your established plants to take advantage of limited space in your garden. You can plant two seasons in most growing regions.

3. When to Harvest Senposai Greens

Senposai greens are fast-growing and will be ready to harvest in as little as four to five weeks. The best way to harvest is simply to pluck off the lower leaves. You should leave eight leaves on the plant, counting from the center out. This allows enough vegetative material to keep the plant healthy.

Gardeners will want to ensure they harvest all of their growing senposai before the summer heat kicks in. It would be best if you planned on removing senposai for a month or two during the summer to let the soil rest. You can turn the soil with fertilizer during the rest so that your garden is ready for late summer planting.

4. What to Do About Bolting

Bolting happens when a senposai plant switches from vegetative growth to flowering. When bolting happens, the leaves will begin to harden and will have a bitter flavor. Early bolting is a common problem in regions that experience temperature changes from cold to hot weather rapidly. There are some simple strategies gardeners can employ to prevent the fast-growing senposai from bolting early.

The Causes and Solutions to Early Bolting

Research on the causes of Brassica bolting reveals that the length of the day plays a significant role in causing early bolting. It turns out that for many Brassica species, the ideal length of daylight is eight hours. Plants grown during longer daylight periods bolted quicker. Gardeners can use row cover to limit the daylight’s intensity.

High temperatures also play a role in early bolting, but research has not concluded whether lack of water due to high temperatures is a greater factor causing premature bolting. Either way, you can avoid early bolting due to temperature or dry soil during hot weather using a layer of mulch around plants or ground cover companion plants that hold in surface moisture.

5. Correctly Watering Senposai

Many Brassica plants are picky about watering, and senposai is no different. Senposai requires moist soil that drains well.

Avoid allowing the soil to dry because senposai is easily stressed and will bolt quickly. You should give water carefully around the base of the plant. Avoid spraying the leaves with water to help prevent disease and bacteria growth.

How To Use Senposai in Meals

Senposai leaves can be eaten raw in salads, but it’s most common to use it in stir fry recipes and soups. It’s delicious when sauteed with garlic and butter. At home, you can use senposai in any recipe that calls for spinach or cabbage. Use it as a tender alternative to any recipe that uses cabbage, too.

Common Pests and Diseases

Senposai grows best during spring and fall, which is unfortunate because those are also seasons when pests are hungry. Spring larvae develop when the soil temperature warms and emerge as hungry caterpillars ready to devour tender seedlings.

Then in the fall, a whole host of pests consume as many greens as possible to prepare for winter. If you don’t immediately treat the signs of pests and diseases, they can quickly destroy your entire crop.

Signs of Pests

Pests will usually leave tell-tale signs when they are eating your garden. Learning the signs of bugs can help you treat the problem before an infestation happens. You should look for leaves with irregular holes and chewed edges as the first sign of pests. You may even spot insects on your plants.

What Types of Insects Are Common to Senposai

The types of insects will depend on the location you live, but some of the common pests include cabbage loopers, harlequin bugs, cutworms, aphids, mites, flea beetles, slugs, and snails. Mice, voles, and birds will also feed on senposai plants.

It’s best to avoid using chemical pesticides on your plants, and these should be considered only a last resort. There are organic methods that you should consider first.

A great way to treat insects that eat the leafy greens is to sprinkle diatomaceous earth on growing plants between waterings. A spray mixture of 70 percent neem oil will work to kill aphids and spider mites.

Rings of diatomaceous earth, copper wire, and sharp objects around the base of plants will deter slugs and snails. You can also use baited slug and snail traps or even make them at home to kill these pests before they eat your greens.

Common Diseases in Senposai Crops

Senposai is susceptible to numerous diseases common to other Brassica varieties. Root rot is common in senposai crops that receive too much water. Wilt and blight are also common.

You’ll notice brown or black spots on the leaves, which eventually wilt and die. Bacterial and viral infections often come from the soil and can be carried from different varieties.

If you see any signs of root rot, viral, or bacterial infection, you need to remove and discard the infected plant and treat the soil. It’s an excellent preventative method to avoid planting crops of Brassica species in the exact location for more than three seasons. You can rotate other crops that are known to replenish the soil, like legumes.

Conclusion

  • Senposai is a hybrid cross of Japanese mustard spinach and regular cabbage.
  • The leafy greens taste like cabbage but grow like mustard.
  • Gardeners should start with a new seed each season because senposai is an F1 hybrid that won’t produce reliable results.
  • Senposai grows best in the spring and fall when days are around eight hours long.
  • Bolting is due to long days and high temperatures, which gardeners can avoid using shade cloth.
  • Seeds can be direct sown or started indoors two weeks after the last frost.
  • Plant seedlings 18 inches apart to allow for excellent growth.
  • Harvest leaves after 30-45 days, leaving eight leaves from the center to encourage continued growth.

It’s most commonly eaten in stir-fry and soup recipes, but you can also use it in salads.
Insects and diseases can kill entire crops, and gardeners can take steps to prevent both.

If you have always wanted to grow a delicious leafy green, but you live in a region with short growing seasons, the senposai is an excellent choice. It matures quickly in as little as 30 or 45 days, allowing you to harvest a delicious crop in a short time.

You can even get two growing seasons in many parts of the U.S. by planting in the spring and fall. Growing senposai is a fun way to add a rare and exciting leafy green vegetable to your garden.

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