Spearmint is a member of the mint family and is a common flavor in breath mints and gum. The leaves of spearmint are edible and can be added to salads, smoothies, certain desserts, and even as a flavoring agent for water.
I. Appearance and Characteristics
Spearmint, a species of mint (mentha) scientifically classified as Mentha spicata (,) also known as garden mint, common mint, lamb mint and mackerel mint, is native to Europe and southern temperate Asia, extending from Ireland in the west to southern China in the east. It is naturalized in many other temperate parts of the world, including northern and southern Africa, North America, and South America.
Mentha spicata was first described scientifically by Carl Linnaeus in 1753. The epithet spicata means ‘bearing a spike’.
The species and its subspecies have many synonyms, including Mentha crispa, Mentha crispata, and Mentha viridis.
Spearmint is a perennial herbaceous plant. It is 30–100 cm (12–39 in) tall, with variably hairless to hairy stems and foliage, and a wide-spreading fleshy underground rhizome from which it grows. The leaves are 5–9 cm (2–3+1⁄2 in) long and 1.5–3 cm (1⁄2–1+1⁄4 in) broad, with a serrated margin. The stem is square-shaped, a defining characteristic of the mint family of herbs. Spearmint produces flowers in slender spikes, each flower pink or white in colour, 2.5–3 mm (0.098–0.118 in) long and broad. Spearmint flowers in the summer (from July to September in the northern hemisphere), and has relatively large seeds, which measure 0.62–0.90 mm (0.024–0.035 in). The name ”spear” mint derives from the pointed leaf tips.
Mentha spicata varies considerably in leaf blade dimensions, the prominence of leaf veins, and pubescence.
Spearmint can readily adapt to grow in various types of soil. Spearmint tends to thrive with plenty of organic material in full sun to part shade. The plant is also known to be found in moist habitats such as swamps or creeks, where the soil is sand or clay.
Spearmint ideally thrives in soils that are deep, well-drained, moist, rich in nutrients and organic matter, and have a crumbly texture. The pH range should be between 6.0 and 7.5.
II. How to Grow and Care
Sunlight
Spearmint needs sufficient sunlight during the whole growth period. It is best to place potted plants on windows or balconies with good light. Sufficient sunlight is conducive to the accumulation of organic substances in the plant. The longer the sunlight, the higher the contents of mint camphor and mint oil. Without enough light, its leaves become thin, turn yellow, or even fall off. Its fragrance becomes faint and it becomes susceptible to disease.
Temperature
Spearmint is widely distributed in the temperate zones of the northern hemisphere, and is resistant to heat and cold. It likes moisture, but cannot tolerate waterlogging. It needs a large amount of water during early and middle growth periods. It grows best between 20 to 30 ℃. Seedlings can withstand -5 ℃. The above-ground part withers when the temperature drops to around -2 ℃.
Watering
Spearmint prefers moisture but cannot tolerate waterlogging. Water every 3-4 days depending on the condition of the soil. Determine soil moisture by inserting a finger into the flowerpot soil. If the soil is hard and dry, it needs to be watered immediately.
It is best to water spearmint with rainwater and distilled water, because tap water may contain a lot of calcium, magnesium, and other mineral salts, and its long-term use tends to cause soil hardening. Use more water in dry weather and pay attention to drainage in the rainy season.
Soil
Spearmint adapts to a wide range of soil as long as the soil is not too barren or too acidic. However, the best soil is permeable, well-drained, fertile loam that retains water and is rich in humus. It likes fertilizer and requires nitrogen, phosphorus, and potassium. Nitrogen is most important, as it helps leaves and stems to develop.
Spearmint is a shallow-rooted plant. It roots grow about 15 cm down and around 30 cm horizontally. Choose a flowerpot or a planting area big enough for it. The suitable pH of soil is 5.5-7.5 and neutral soil is best.
Fertilizing
An appropriate amount of fertilizer makes spearmint grow better. Quick-acting fertilizer is best applied frequently in small amounts. If the plant is very short, grows slowly, or shows yellow leaves, it may need fertilizer. It likes fertilizer, and nitrogen fertilizer is most important. With an appropriate amount of nitrogen fertilizer, spearmint will grow vigorously. Potassium fertilizer should also be properly applied.
Generally, watered-down fertilizer can be applied once every two weeks. In summer, the plant is growing the most while the temperature is high and water evaporation is fast. Use a low concentration of liquid fertilizer and apply more in summer, perhaps once a week. In winter, spearmint grows slowly or stops growing, and no fertilizer is required.
Planting Instructions
Sow spearmint in the spring. Expose the soil to sunlight before sowing so as to kill harmful microorganisms. If you worry about uneven sowing, mix the seeds with fine soil in advance and then spread the mixture. Transplant when the seedling is around 13 cm tall.
Pruning
During the growth period, spearmint needs pruning to keep it lush and beautiful. Remove the terminal bud one month after planting. Cut the bud of the main branch by 5 to 8 cm. The buds of other branches should be properly pruned to promote the development of lateral branches.
Cut long branches back to 8 to 10 cm long. Branches affected by pests and diseases or dead branches should be pruned immediately. In winter, the plant is dormant, so only cut off dead branches and leaves.
Propagation
Spearmint propagates strongly. It can reproduce asexually, such as by dividing and cutting. Seed propagation is commonly adopted for breeding.
Cutting is an easy way to make new plants. Cut a healthy and robust branch in late spring or early summer with a length of around 10 cm, and remove the lower leaves. Soak it in clear water for 1-2 hours and insert it in a sand bed for rooting. It takes around 2 weeks to root. During rooting, watch for rust disease and spot blight. Transplant healthy seedlings to flowerpots.
Pests and Diseases
- Fungal diseases
Fungal diseases are common diseases in spearmint. Two main diseases are rust and leaf spot. Puccinia menthae is a fungus that causes the disease called “rust”. Rust affects the leaves of spearmint by producing pustules inducing the leaves to fall off. Leaf spot is a fungal disease that occurs when Alternaria alernata is present on the spearmint leaves. The infection looks like a circular dark spot on the top side of the leaf. Other fungi that cause disease in spearmint are Rhizoctonia solani, Verticillium dahliae, Phoma strasseri, and Erysiphe cischoracearum.
- Nematode diseases
Some nematode diseases in spearmint include root knot and root lesions. Nematode species that cause root knots in this plant are various Meloidogyne species. The other nematode species are Pratylenchus which cause root lesions.
- Viral and phytoplasma diseases
Spearmint can be infected by tobacco ringspot virus. This virus can lead to stunted plant growth and deformation of the leaves in this plant. In China, spearmints have been seen with mosaic symptoms and deformed leaves. This is an indication that the plant can also be infected by the viruses, cucumber mosaic and tomato aspermy.
III. Uses and Benefits
- Ornamental uses
Spearmint (Mentha spicata) is a feature of many herb gardens where it is grown as a culinary herb. The plant’s white flowers are of secondary interest but are nevertheless attractive to look at and inviting to bees. The plant is vigorous and very hardy, and extremely easy to grow, particularly with herbs and vegetables like tomatoes, sage, and thyme. It also makes a great addition to cottage, informal, and wildlife gardens.
- Culinary uses
Spearmint leaves are infused in water to make spearmint tea. Spearmint is an ingredient of Maghrebi mint tea. Grown in the mountainous regions of Morocco, this variety of mint possesses a clear, pungent, but mild aroma. Spearmint is an ingredient in several mixed drinks, such as the mojito and mint julep. Sweet tea, iced and flavored with spearmint, is a summer tradition in the Southern United States.
- Other uses
Spearmint is used for its aromatic oil, called oil of spearmint. The most abundant compound in spearmint oil is R-(–)-carvone, which gives spearmint its distinctive smell. Spearmint oil also contains significant amounts of limonene, dihydrocarvone, and 1,8-cineol. Unlike oil of peppermint, oil of spearmint contains minimal amounts of menthol and menthone. It is used as a flavoring for toothpaste and confectionery, and is sometimes added to shampoos and soaps.
Traditional medicine
Spearmint has been used in traditional medicine.
Insecticide and pesticide
Spearmint essential oil has had success as a larvicide against mosquitoes. Using spearmint as a larvicide would be a greener alternative to synthetic insecticides due to their toxicity and negative effect to the environment.
Used as a fumigant, spearmint essential oil is an effective insecticide against adult moths.
IV. Harvesting and Storage
Spearmint leaves can be used fresh, dried, or frozen. The leaves lose their aromatic appeal after the plant flowers. It can be dried by cutting just before, or right (at peak) as the flowers open, about one-half to three-quarters the way down the stalk (leaving smaller shoots room to grow). Some dispute exists as to what drying method works best; some prefer different materials (such as plastic or cloth) and different lighting conditions (such as darkness or sunlight). The leaves can also be preserved in salt, sugar, sugar syrup, alcohol, or oil.
Find Where to Buy the Best Spearmint (Mentha spicata)
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