Amaranthus: Sow in Love with Your UK Tropical Garden

Amaranthus, commonly known as amaranth, is a vibrant and versatile plant that can add a dramatic flair to your UK tropical garden. Known for its striking foliage and eye-catching flower spikes, amaranth is as functional as it is beautiful, with some varieties being grown as ornamental plants, while others are cultivated for their edible leaves and seeds. Here’s everything you need to know about growing amaranth in your garden, from propagation to care, and a bit of its rich history.

History of Amaranthus

Amaranthus has a long history, dating back thousands of years. It was one of the staple crops of the Aztecs and was considered sacred, used in rituals and as a food source. The plant has since spread across the globe, adapted to various climates, and is now grown in many parts of the world for its nutritional and ornamental value. In recent years, amaranth has gained popularity for its resilience, ease of growth, and striking appearance in garden landscapes.

Propagation: How to Start Your Amaranth

Amaranthus is easily propagated from seed, making it an accessible plant for gardeners of all levels.

1. Sowing Seeds: Amaranth seeds are small but straightforward to handle. They can be sown directly into the ground once the danger of frost has passed, usually around late May or early June in the UK. Alternatively, seeds can be started indoors about 6-8 weeks before the last expected frost, then transplanted outdoors.
2. Seedling Care: If starting indoors, sow seeds in trays filled with a light, well-draining potting mix. Keep the soil moist and place the trays in a warm, bright location. Germination typically occurs within 7-14 days. Once seedlings have two sets of true leaves and the outdoor temperatures are consistently above 10°C (50°F), they can be gradually acclimatized to outdoor conditions before being planted out.
3. Transplanting: Space the seedlings about 30-45 cm (12-18 inches) apart in a sunny location with well-drained soil. Amaranth thrives in warm conditions, so ensure they are planted in a spot that receives plenty of sunlight.

Best Varieties for UK Gardens

Amaranthus comes in a variety of species and cultivars, each offering unique colors, textures, and growth habits. Here are a few that are particularly well-suited to UK tropical gardens:

1. Amaranthus caudatus (Love-Lies-Bleeding): Known for its cascading, deep red flower spikes, this variety adds a dramatic, tropical feel to any garden.
2. Amaranthus tricolor (Joseph’s Coat): This variety is prized for its multicolored foliage, with leaves that range from red and yellow to green, providing a stunning display of color.
3. Amaranthus cruentus (Purple Amaranth): With its tall, purple flower spikes and edible leaves, this variety serves both ornamental and culinary purposes.
4. Amaranthus ‘Oeschberg’: A compact variety with dark burgundy leaves and flowers, perfect for smaller gardens or container planting.

Self-Seeding and Weediness

One question many gardeners have is whether amaranth will self-seed and potentially become a weed. The answer depends on the variety and growing conditions:

• Self-Seeding: Amaranth can indeed self-seed, especially if allowed to go to seed and if the seeds are not harvested. In warmer climates, this might lead to amaranth popping up in unexpected places. However, in the UK, where winters are colder, self-seeding is less aggressive. Any volunteers that do appear can usually be easily removed or transplanted.
• Weediness: While amaranth is not considered a weed in the traditional sense, its ability to self-seed means it can sometimes appear where it’s not wanted. Regularly deadheading the flowers before they set seed is an effective way to control this.

Care and Maintenance

Amaranth is relatively low-maintenance, but following a few key care tips will ensure it thrives in your garden:

1. Watering: Amaranth is drought-tolerant once established but benefits from regular watering, especially during dry spells. Ensure the soil remains evenly moist but not waterlogged.
2. Feeding: Amaranth is not a heavy feeder, but adding compost or a balanced fertilizer to the soil before planting can give it a good start. If you notice slow growth or pale leaves, a light feeding with a nitrogen-rich fertilizer can help.
3. Pruning: Regular deadheading will not only prevent unwanted self-seeding but also encourage more flowers to bloom, extending the display season.
4. Pests and Diseases: Amaranth is generally pest-resistant, though it can occasionally be affected by aphids or leaf miners. These can be managed with insecticidal soap or by encouraging beneficial insects like ladybirds.
5. Winter Care: Amaranth is an annual, so it will die back after the first frost. The seeds can be collected for planting next year or left in the garden to see if any plants return naturally.

Conclusion

Amaranthus is a show-stopping addition to any UK tropical garden, offering vibrant color, interesting textures, and even edible benefits. With its easy propagation, variety of stunning cultivars, and low-maintenance care, amaranth is a perfect choice for gardeners looking to add a touch of the exotic to their landscape. Whether you choose it for its ornamental value or its ancient history, amaranth will surely be a conversation starter in your garden.

Amaranthus – Grow Guide

Common name: Amaranth, Love-lies-bleeding
Family: Amaranthaceae
Type: Half-hardy annual (some perennial in warmer climates)
Hardiness: RHS H2 – frost-tender; grown as a summer annual in the UK
Ultimate size: 60 cm–2 m tall × 40–60 cm wide (varies by species)

Overview

Amaranthus is grown for its bold foliage and dramatic tasselled flower heads, which can be upright or cascading, in shades of red, burgundy, lime, gold, and green. It is equally valuable as an ornamental plant and, in some species, an edible crop (leaves and seeds). Perfect for exotic borders, cutting gardens, and containers.

Position

• Light: Full sun
• Needs warmth and shelter for best colour and growth
• Avoid cold, exposed sites

Soil

• Type: Fertile, free-draining soil
• Tolerates a wide range of soils but dislikes waterlogging
• pH: Neutral to slightly alkaline

Sowing & Planting

• Sow indoors: March–April at 18–21 °C
• Direct sow: May, once soil is warm and frost risk has passed
• Transplant outdoors after hardening off
• Space plants 30–50 cm apart, depending on variety

Watering

• Water regularly during establishment
• Once growing strongly, Amaranthus is fairly drought tolerant
• Avoid letting young plants dry out completely

Feeding

• Moderate feeder
• Apply a balanced fertiliser at planting
• Avoid excess nitrogen, which promotes leaves at the expense of flowers

Growth & Habit

• Fast-growing, upright or spreading annual
• Large leaves in green, red, or variegated forms
• Flowers form long tassels or upright plumes from midsummer onwards

Flowering

• Months: July–October
• Flowers: Tassels or plumes in deep red, crimson, lime, gold, or bronze
• Excellent for cut flowers and drying

Maintenance

• Minimal maintenance
• Stake tall varieties in exposed sites
• Remove spent flowers if self-seeding is not wanted
• Leave seed heads for winter interest or wildlife

Propagation

• Seed: Easy and reliable
• Self-seeds freely in warm summers

Pests & Problems

• Generally trouble-free
• Slugs may attack young seedlings
• Poor growth in cold or waterlogged soil

Garden Use

• Exotic and tropical-style borders
• Cut flower and dried flower gardens
• Containers (compact varieties)
• Excellent companion plants:
  • Cannas
  • Ricinus
  • Cosmos
  • Cleome

Quick Reference Table