Knowing your climate zone will help you decide the best time to sow the vegetables, herbs and flowers you want to grow, and which varieties should perform well in your garden. Growing plants that are suited to your climate zone will usually give you the best results in your garden.
This How to Grow guide details everything a home gardener needs to know to plant, grow and care for Amaranth (Amaranthus sp.).
Amaranth (Amaranthus sp.) can be grown for its foliage or its flowers. Varieties grown for their ornamental foliage have flowers but they are insignificant rather than showy. Globe amaranth (Gomphrena globosa) is a different species; refer to individual product listings for growing instructions.
Amaranth is one of my favorite plants to grow for its beautiful long-lasting flowers and nutritious seeds and greens. However like any plant, amaranth is susceptible to fungal diseases that can cause devastating root and stem rot. If left unchecked, rot can rapidly spread, killing the plant.
In this article, I’ll share the common causes of rot in amaranth and effective solutions to prevent it With proper care, you can keep your amaranth thriving and rot-free for years of enjoyment.
What Causes Rot in Amaranth Plants?
Several factors can contribute to the development of fungal rot diseases in amaranth plants:
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Excess Moisture – Fungal pathogens thrive in wet conditions. Overwatering and poor drainage cause water to pool around roots creating the perfect breeding ground for fungal infections.
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Wounds or Damage – Open wounds from pests, tools, or rough handling provide an entry point for fungal spores. Damage to roots is especially problematic.
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Dense Growth – Crowding amaranth plants prevents proper air circulation, which allows fungal spores to accumulate.
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Cool Temperatures – Amaranth prefers hot, dry conditions. Cool, damp weather favors fungal growth and infection.
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Weakened Plants – Already stressed plants, such as those lacking proper nutrients, are more vulnerable to fungal diseases taking hold.
Recognizing the Signs of Rot
To effectively treat and prevent rot, it’s important to promptly identify symptoms:
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Wilting – Leaves droop and flag as rot limits the plant’s ability to take up water and nutrients.
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Discolored Stems – Stems turn dark brown or black at soil level as rot spreads up from the roots. Mushy, disintegrating stems soon collapse.
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Foul Odor – Rotting plant tissue gives off a distinctive rotten smell, especially when stems are broken.
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Root Decline – Inspecting roots reveals mushy, discolored tissue with foul odor. Healthy white roots are replaced by brown and black decay.
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Premature Leaf Loss – Rot interrupts the transport of water and nutrients, causing leaves to yellow, wilt, and drop early.
Effective Preventative Measures
While some fungal diseases are difficult to control once established, taking proactive measures can help prevent problems in the first place:
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Avoid Excess Moisture – Water only when the top few inches of soil become dry. Ensure pots and beds drain well.
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Allow Space for Airflow – Give amaranth plants 1-2 feet between them to encourage air circulation and rapid drying.
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Use Sterilized Tools – Disinfect shears, trowels, and other tools before using to prevent spreading spores.
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Promote Vigor – Apply balanced fertilizer and prune regularly to keep plants robust and better able to resist diseases.
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Scout for Issues – Routinely inspect plants for early signs of pests or damage that could allow fungal invasion.
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Employ Crop Rotation – Avoid planting amaranth in the same spot each year to prevent disease buildup in soil.
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Control Weeds – Remove weeds promptly to eliminate alternate hosts and sources of fungal inoculum.
Treating Existing Rot in Amaranth Plants
If rot is detected, aggressive measures are needed to save the plant and protect other vegetation:
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Remove Infected Parts – Prune out all visibly diseased roots, stems, and leaves, cutting at least 2 inches into healthy tissue.
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Disinfect Tools – Prevent spreading fungal spores by sterilizing shears after each cut. Dip tools in isopropyl alcohol or a 1:10 bleach solution.
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Improve Soil Drainage – Saturated soil prolongs fungal issues. Incorporate compost, sand, or gravel to improve drainage around plants.
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Space and Prune – Opening up growth improves air movement to quickly dry foliage and soil.
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Allow Soil to Dry – Hold off watering until top several inches of soil are crumbly and moist, not wet.
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Apply Fungicides – Treat remaining plants with broad spectrum fungicides containing mancozeb, myclobutanil, or chlorothalonil.
When to Sow Amaranth Seeds
Amaranth is a warm season crop. Use the table below to identify the best time of year to sow amaranth seeds in your climate.
| JAN | FEB | MAR | APR | MAY | JUN | JUL | AUG | SEP | OCT | NOV | DEC |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Cool | |||||||||||
| Temperate | |||||||||||
| Sub-Tropical | |||||||||||
| Tropical | |||||||||||
| Arid |
- Includes: Alice Springs, Mildura, Albury-Wodonga, Shepparton, Wagga Wagga, Dubbo
- Hot dry summers, winters can be warm or cool depending on the region. Includes a large area of central Australia from the WA coast to Charleville (Qld), Tamworth (NSW) and Albury-Wodonga (NSW/Vic).
- Includes: Darwin, Cairns, Townsville, Exmouth
- High humidity summers with most rainfall in summer and dry, warm winters. Includes northern Australia from Exmouth (WA) across to south of Townsville (Qld).
- Includes: Brisbane, Bundaberg, Coffs Harbour, Gold Coast, Hervey Bay, Mackay, Rockhampton, Sunshine Coast
- Warm humid summers with high summer rainfall and mild winters. Includes coastal Queensland and northern NSW from north of Mackay to just south of Coffs Harbour.
- Includes: Sydney, Perth, Adelaide, Newcastle, Toowoomba, Central Coast NSW, Wollongong, Bunbury
- Moderate humidity and reliable rainfall, with four distinct seasons. Includes coastal areas from north of Port Macquarie to south of Woollongong in NSW, coastal SA and the southeastern coast of WA.
- Includes: Melbourne, Canberra, Hobart, Launceston, Ballarat, Bendigo, Geelong, Mt Gambier
- Low humidity with most rainfall in winter; hot dry summers and cold winters. Some regions will experience frosts and snow. Includes coastal areas of south-eastern Australia and alpine areas of Victoria, NSW and Tasmania.
Amaranth plants are best grown in full sun. Choose a location that will receive at least 6 hours of full sun each day.
Amaranth plants need a well drained soil enriched with plenty of organic matter. Prepare soil by weeding it thoroughly, digging it over to loosen it and adding aged animal manure or compost. Keep the area free of weeds until planting. Learn more about preparing soil for planting here.
Amaranth plants can be grown in containers. If possible choose a variety that’s recommended for container growing. Use a good quality potting mix and make sure your container is large enough for mature plants; a minimum of 20 litres is recommended for amaranth. During the growing season, keep in mind that container grown plants may need additional fertiliser to encourage healthy growth.
How to Sow Amaranth Seeds
Amaranth seeds do not require any treatment (eg soaking, stratification) before sowing.
Amaranth seeds grow best when they are sown directly into the garden.
- Sow seeds directly in the garden 3mm deep and 60cm apart.
- Keep soil moist but never wet or dry.
- Seeds should germinate in around 7-10 days at a soil temperature of 20-25°C.
- Young seedlings will need protection from pests, pets and weather until they are established.
Amaranth is a tender crop that’s sensitive to frost. Do not transplant seedlings or sow seeds outside until all danger of frost has passed.
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FAQ
What causes holes in amaranth leaves?
How can the root rot disease be prevented?
What is a natural anti rot for plants?
Can amaranth plant diseases be prevented?
A: Yes, you can prevent amaranth plant diseases by practicing good sanitation in your garden, including removing any infected plants or leaves immediately and keeping your tools clean between uses. Q: Can I eat amaranth plants affected by diseases?
How do I get rid of pests in my amaranth plant?
If you already have a pest infestation in your amaranth plants, here are some methods you can use to control them: 1. Insecticidal Soap Insecticidal soap is a safe and effective way to control aphids, spider mites, and other soft-bodied insects. Simply spray the affected areas of the plant with the soap solution. 2. Neem Oil
Are amaranth plants immune to pests?
Amaranth is a popular plant with edible leaves and seeds. It is also known as pigweed, redroot, and love-lies-bleeding. However, amaranth plants are not immune to pest infestations. In this article, we will discuss some common amaranth plant pests and how to prevent and control them. 1. Aphids
How do you care for Amaranth?
Amaranth is easy to care for and requires little maintenance. While the seedlings are young, it is important to remove any weeds from around the plants to prevent competition. Applying a layer of mulch will help to prevent weeds and conserve soil moisture.