How to Plant, Grow, and Maintain the Globe Amaranth Plant

Globe amaranth is a tropical annual that has globe-shaped blooms that last for a long time, and they come in a range of colors. They work well in rock gardens, beds, borders, and xeriscapes as they’re very tolerant to drought. This plant is one of the 90 Gomphrena species of flowering plants that you find in the Amaranthaceae family. It’s native to northern and central South America, and you’ll find classic magenta flowers dotting along the landscape. Cockscomb, Love Lies Bleeding Amaranth, and Spinach are close relatives to globe amaranth.

The bright flower heads look a little like clover, and they feature tubular bracts instead of petals. If you touch them, you’ll notice that they’re just like strawflowers as they’re very paper and stiff. Each bract has tiny yellow or white flowers that you can only see at close range, and this is a very tender annual in zones two to eight. It’ll start to bloom in this climate early in the summer and continue through fall until the first hard frost hits.

If you live in zones 9 to 11, you can grow globe amaranth as an annual and remove it in the fall or grow it as a short-lived perennial. It’s self-sowing, so it may produce more plants, but the seeds have a very low germination rate. Due to hybridization, there are now a range of colors to choose from, including pink, magenta, lilac, red, purple, white, and orange. In this quick guide, we’ll outline everything you need to know to grow and care for globe amaranth.

1 Pink Globe Amaranth
Globe amaranth is a very cheerful, bright flower that can stand out in your garden from spring until late fall.

Globe Amaranth – General Information

Attracts: Butterflies, bees, and other pollinators
Bloom Time: Early summer to the first frost
Common Diseases/Pests: Thrips, aphids, damping off, leaf spot, gray mold, and powdery mildew
Companion Planting: Mexican petunia, celosia, marigold, and zinnia
Exposure: Full sun
Family: Amaranthaceae
Flower and Foliage Colors: Magenta, lilac, pink, red, purple, orange, green, and white
Genus: Gomphrena
Growth Rate: Slow
Hardiness Zones: 2 to 11
Height: 6 to 48 inches
Maintenance Needs: Low
Native to: Northern and South Central America
Planting Depth: ⅛ inch
Plant Type: Short-lived perennial or tender annual
Soil Drainage: Well-draining
Soil pH: 6.1 to 7.5
Soil Type: Average
Spacing: 12 to 18 inches
Species: Globosa
Spread: 8 to 24 inches
Tolerance: Drought, deer, poor soil
Uses: Borders, beds, containers, xeriscapes, rock gardens
Water Needs: Medium

History and Cultivation of the Globe Amaranth

As this is a tropical plant by nature, it has a very high tolerance for humidity and heat, and it thrives in sunshine. It has a long taproot, and this lends to the above-average drought tolerance, but it prefers to have consistent moisture, especially when it germinates and is a seedling. When it comes to picking out soil, it can do well in everything from clay to loam as long as it has good drainage. This plant has a very upright growth habit, and it tends to get more leggy unless you pinch the flowers early in the spring months.

You can choose from a range of mature heights for globe amaranth, and they range from the six-inch dwarf cultivar to four-foot options. And while some may have taller growth habits, they are generally compact plants that will spread between 8 to 24 inches. The upright stems have vertical branching too, and the leaves are covered in fine hair and display a thin purple margin. They tend to grow in pairs opposite of one another, and this plant works to fix carbon using the C4 pathway. So, this means that globe amaranth is genetically predisposed to breathe differently than other plants. This allows the plant to retain moisture, conserve energy, and survive in soil that has lower nitrogen content as you’ll find in tropical climates.

The leaves, flowers, roots, and seeds on globe amaranth have immune-boosting phytochemicals and antioxidants in them, and many herbalists have used them to help treat a range of issues, including respiratory problems and GI upset. This plant originally came to the United States in the 1700s, and many people choose to grow it as an ornamental, including a young Thomas Jefferson at his residence in Shadwell.

In the gardens at Monticello, globe amaranth is the highlight of the space. The blossoms are long-lasting and colorfast, and they’re used in ceremonial gardens throughout Hawaii. However, this species is also classified as being invasive in Cuba, Costa Rica, and parts of Hawaii.

Popular Globe Amaranth Cultivars

Picking out different globe amaranth cultivars can be fun because there are so many sizes and colors available. A few popular options include:

  • Audray White – This cultivar offers crisp white flowers that sit on 18-inch stems. It’s a middle-sized variety that works placed in the middle of your borders or beds or in containers. It has a neutral tone that makes it a great buffer for plants of different hues.
  • Fireworks – If you want to add an impressive specimen in your garden, Fireworks is it. This plant can get between 36 and 48 inches tall, and it has very bright yellow flowers. It’s a great choice to help grab attention when you go into the garden.
  • Mixed Gnome – This is a grab bag of purple, pink and white mixed flowers that grow on a very low profile and top out at six inches. It’s perfect to plant at the front of your borders or in mixed containers.

2 Globe Amaranth Cultivars
There are dozens of cultivars you can get for this plant that come in a range of colors and styles to suit your wants and needs.

Globe Amaranth Care

You normally get globe amaranth from inexpensive seedling packs from nurseries. It’s a very low-maintenance plant that likes to be in well-drained soil and full sun. It will bloom freely from spring until late fall without any deadheading, and it takes nicely to clipping a few blooms off to add to a vase on your table. To keep it healthy, you’ll:

Fertilizer

This plant is generally a very light feeder, and if you add a mulch with compost around them, you can skip fertilizing them entirely.

Light

Globe amaranth will grow well in partial shade to full sun. If you give it too much shade, it’ll reduce how much it blooms and cause the plant to grow lanky as it stretches to meet the sun.

Soil

This plant isn’t picky about soil, and it grows very well in your average garden soil or something that is slightly sandy. They will still bloom if you plant them in a heavy clay-based soil, but it’ll stunt the height. This plant also doesn’t like alkaline soil conditions, and you want a pH to range from 6.1 to 6.5.

Temperature and Humidity

Globe amaranth is hardy, and it’ll grow in virtually any planting zone. You don’t want to put them outside until the soil temperatures start to warm up in the spring months.

Water

Make a point to water these plants regularly. They can tolerate dry spells, but it will grow the best if you keep the soil consistently moist. They need roughly an inch of water a week from irrigation or rainfall to thrive.

Growing Globe Amaranth – Conditions

To grow this plant in your garden, you’ll want to wait until the last frost date of the season passes before you transplant anything. You can directly sow the seeds or transplants if you have no worry of frost, like you’ll see in zones 9 to 11. Pick a spot that gets full sun. Provided the soil drains very well, it can be anything from clay to organically-rich loam.

Ideally, the pH will range from 6.1 to 7.5, or slightly acidic to just barely alkaline. To learn about the soil’s characteristics in your yard, you may want to do a soil test with your local agricultural extension office. Adding compost to the soil is one way to boost the acidity in the soil, and mixing in lime will reduce it. Given the fact that this plant grows on a longer taproot, you’ll need to make sure your garden soil has a crumbly texture to a depth of 12 inches at a minimum and add in any amendments as necessary.

Also, keep the taproot in mind when you grow globe amaranth in containers. The taller the plant, the deeper your pot will have to be, and depths of 12 to 24 inches should be fine. Sow your seeds ⅛-inch deep and scatter a few seeds every four to six inches while covering them lightly with soil. To transplant your thinned out seedlings, bury the individual biodegradable containers to the same depth as the soil in the cells in your chosen spot.

It’s not necessary to fertilize globe amaranth plants. However, if you’re someone who regularly applies a liquid fertilizer to your space, pick one that has a lower nitrogen content. Make sure the moisture levels are even, but make sure you don’t overdo it. Overwatering can make your plants prone to damping off, and this is a fungal disease that causes your plants to fall over and die off. When the seedlings develop one or two sets of true leaves, thin them out to roughly 12 to 18 inches apart. Good circulation will also help head off fungal disease issues.

As your globe amaranth matures, give it no more than an inch of water a week through supplemental watering and rainfall. Always aim your watering can or hose at the soil level and not on the foliage to help inhibit fungal growth. When you see the first flower buds start to form, you can pinch them off to encourage your plant to take on a bushier form. If you have leggy plants, you’ll have to stake them to keep them upright.

Throughout the spring and summer growing months, periodically cutting flowers for arrangements or deadheading them will help stop leggy growth and encourage more blooms. For the best results, get rid of a portion of the stem and not just the flower, at the point where it meets a second stem or where two leaves meet. Since this is a tropical plant, it loves heat but requires higher humidity. It can also survive mild drought conditions, but you’ll get the best results from plants that are in an environment that mimics the tropics.

3 Growing Conditions
The closer you can mimic this plant’s growing conditions, the better the flowers and foliage will look all growing season long.

Propagating Globe Amaranth

You can grow your plants from seeds. Keep in mind the germination will be slow, and it can take anywhere from one to four weeks. The germination rate also tends to be lower, and this means that a large portion of the seeds might fail to sprout. Maturity takes between 85 and 100 days, and you want to make a point to disturb the taproot as little as possible. For annual or perennial cultivation, soak the seeds overnight and start them indoors roughly eight weeks before the last frost date of the season to jumpstart the growing season.

Consider using biodegradable seed starter cells or cardboard egg cartons that you can easily separate to plant them. The seeds are tiny, so try to only get four of them into each cell. Cover the seeds with ⅛-inch potting soil and thin the seedlings out to one per cell when they get one or two sets of mature leaves.

Once the frost danger passes, you want to acclimate your seedlings to the outdoors but putting them outside for a few hours each day for three to five days before you actually plant them. Transplant the individual cells right into deep containers or in the garden after the frost danger passes. To grow them as perennials, you can directly sow your seeds in the garden, but they may not bloom until year two.

Potting and Repotting

Globe amaranth does surprisingly well in container gardens when you use it as a tall accent plant. You can combine it with a mounding plant like vinca or petunias as a trailing plant to get a very lush, full look. Put it in a container that has larger drainage holes and keep in mind that you’ll have to water your container plants more frequently than plants in the garden. You won’t need to repot it.

Overwintering

Since globe amaranth is traditionally a true annual that has a life cycle that will only go through one growing season, you don’t need to worry about overwintering it. Instead, you pull it up and discard it late in the fall when it dies back.

Harvesting and Preserving Globe Amaranth

Many people grow globe amaranth as an ornamental plant, but you can also harvest the tender flowers, young leaves, sprouts, and seeds to eat if you like. Also, the intense coloring on the traditional magenta plants make a nice natural food dye. You can easily pick through the sprouts and eat them as microgreens, along with the tender foliage before it gets tough and fuzzy.

Harvest the flower heads as desired by carefully pinching them off at the base of the stem where they meet a pair of leaves or another stem. Pick the flowers that are almost fully but not 100% open. At the end of the active growing season, you can harvest this plant’s seeds and roots. To harvest the roots, you’ll dig up your plant when it finishes blooming before the first frost hits. Cut the stems off at the plant’s crown and rinse away the soil before you use them.

To harvest your plant’s seeds, you’ll wait until the flower heads turn tan and dry. Carefully snip them off and pull them apart over a light colored paper or cloth to see the seeds better. You’ll separate and release them from the chaff as you work. If you’re gathering the seeds to sow next year, note that the seeds of any hybrids aren’t always viable, and when they are, they are very prone to producing traits that are different from the parent plant.

Young leaves and tender sprouts should get eaten as soon as you can after you pick them, and they work well tossed into a salad or into a stew. You also want to use fresh flowers right away, and they can make pretty garnishes or an earthy tea if you brew them. If you want to dry the flower stems when they’re as colorful as possible, you’ll:

  • Cut the stems as soon as the flowers are fully open, but you can also include a half-open flower or bud if you like. Avoid any flowers that are starting to fade or go to seed.
  • Whether you keep the foliage attached or remove it is 100% up to you. Gather the stems like you would a bouquet. Bind them with twine, and leave the long ends to suspend them from a nail or hook. Hang them upside down and leave them to dry for three or four weeks. The leaves and stems will turn brown while the flowers stay colorful. You can use full stems in arrangements or cut some of the dried flower heads to brew into tea, add color to potpourri, or make a dye.

You can keep your dried flower heads for up to a year in an airtight jar. Edible roots generally get eaten like you would other root vegetables. Depending on the thickness, they can last for a few days in the refrigerator before they turn limp. You can keep dry seeds in an airtight jar for up to a year. If you see any mold, discoloration, or if you smell odors, get rid of them.

4 Bright Flower Coloring
As a bonus, globe amaranth is one flower that you can dry and it won’t lose the brilliant color on the flowers. This makes it great to use in dried flower arrangements.

Best Ornamental Uses for Globe Amaranth

As this plant is available in sizes that start at six inches and go up to four foot plants, they work well when you plant them in borders, beds, rock gardens, pots, xeriscapes, and window boxes as long as they get full sun. Also, the taller flowers make nice cut flowers for fall or summer centerpieces, and all of the sizes will dry nicely to use in wreaths.

If you plan on growing them in containers, make sure they have larger drainage holes before you fill the container with your soil. No matter where you find them in your garden or landscape, they add welcome pops of color. You can try pairing them with the following plants to fill in spaces:

  • Celosia
  • Marigold
  • Mexican Petunia
  • Salvia
  • Zinnia

Globe Amaranth Pests and Disease Issues

Globe amaranth isn’t hugely prone to problems with diseases or pests, and you should have no issues when you follow the best gardening practices. However, there are a few sap-sucking insects that will destroy the foliage when they latch on and spread diseases. Two of the biggest pests to keep an eye out for are:

  • Aphids
  • Thrips

If you can’t dislodge these bugs with a spray from the hose, you may want to apply neem oil. As for diseases, there are a few that can wreak havoc on your globe amaranth and make it hard for them to thrive. They include:

  • Alternaria Leaf Spot
  • Damping Off
  • Gray Mold
  • Powdery Mildew

Alternaria leaf spots can cause dead brown patches with yellow rings on your plant’s mature leaves. If you leave it unchecked, the entire leaves will curl and turn brown before dying and falling off. You want to discard any infected leaves in the trash and apply a fungicide. Powdery mildew and gray mold are both fungal diseases that will damage the plant’s foliage by producing a fuzzy, gray-hued mold. You can treat them both by picking off the infected leaves and getting rid of them before applying a fungicide.

Damping off is another fungal disease that can occur when your seedlings are oversaturated, and it can cause them to fall over and die. There is no cure for it, and prevention is key. To avoid this issue, you should:

  • Plant globe amaranth in full sun to help keep the plant’s foliage from staying wet when you water it and inviting fungal issues.
  • Follow the spacing recommendations when you plant them because good airflow can prevent moisture buildup.
  • Weed your garden regularly to deter any pests from hanging around and eating your plants.
  • Water at the soil level to keep from soaking the plant’s foliage and making it more prone to fungal issues.
  • Don’t overwater your plants, especially during the seedling stage. The goal is to maintain an even moisture level.

When you grow this plant as an ornamental cultivar, foliage that is under attack by diseases or pests isn’t pretty, but if you can catch it early and treat it, your plants stand a good chance of surviving.  If you plan on growing this plant as an edible, you’ll need to be very careful when it comes to eating infected or infested portions of the plant. You should also only use treatment products that are for edible plants.

Bottom Line

In most growing zones, globe amaranth is a great addition to your garden as an annual plant because it will infuse your garden with spring to frost color and texture. They make wonderful arrangements, and you can dry them and get a bright natural dye too. You can use this quick guide to help your globe amaranth thrive in your space this year.

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