By: Bonnie L. Grant, Certified Urban Agriculturist
Globe amaranth plants are native to Central America but do well in all the USDA plant hardiness zones. The plant is a tender annual, but it tends to reseed itself for years of consistent blooms in the same area. Learning how to grow globe amaranth is easy and its round blooms will attract butterflies and important garden pollinators.
Globe amaranth plants (Gomphrena globosa) grow from 6 to 12 inches (15 to 30 cm.) high. They have fine white hairs covering young growth, which matures to thick green stems. The leaves are oval and arranged alternately along the stem. The blooms of globe amaranth start in June and may last until October. The flower heads are clusters of florets that resemble large clover flowers. They range in color from pink, yellow, white and lavender.
An interesting bit of globe amaranth info is that the flowers dry well. They make excellent additions to everlasting bouquets to brighten the interior of your home. Growing globe amaranth from seed is common in most zones, but the plants are also readily available in most nurseries and garden centers.
Growing globe amaranth is not difficult at all. Start seeds indoors six weeks before the last frost. They will germinate faster if you soak them in water prior to planting. If you wish to sow them outdoors, wait until the soil has warmed and there is no chance of frost.
Choose a site in full sun with good drainage. Globe amaranth plants will grow in almost any soil type except alkaline. Globe amaranth performs best in garden soil, but you can also put them in containers.
Space plants 12 to 18 inches (30 to 45 cm.) apart and keep them moderately moist. Globe amaranth can tolerate periods of dryness, but they perform best with even moisture.
This plant is not susceptible to many disease or pest problems. However, it may get powdery mildew if watered overhead. Watering at the base of the plant or in the morning gives leaves a chance to dry off and prevents this problem.
Globe amaranth plants are old-fashioned additions to dried flower arrangements. The flowers are dried by hanging. Harvest the flowers when they first open with a good length of stiff stem. Tie the stems together and hang the bundle in a cool, dry location. Once dried, they may be used with the stems or remove the flowers and add to potpourri.
The flowers also work nicely in fresh flower arrangements. General care of globe amaranth flowers is the same for any cut floral. Make clean, slightly angled cuts at the ends of the stems and remove any leaves that might sit in the water. Change the water every couple of days and cut off a tiny bit of stem to open up the capillaries again. Amaranth flowers can last up to a week with good care.
Expect the plants to die back when cold temperatures appear, but don’t get distressed! In most USDA zones, the seeds that set after the flower is spent, will germinate in soils after winter.
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Andrey Zharkikh / Wikimedia Commons / CC BY 2.0
The Amaranthus genus is a complicated one, featuring at least 75 annual and perennial species that easily cross-breed and hybridize. Today, most gardeners are familiar with the species as ornamental plants, and many don't even realize that amaranths are also edible plants that can be grown for their grain-like seeds and edible leaves. In fact, this was once the primary reason amaranth served as a staple in home cottage gardens. Historically, the use of amaranth as an ornamental plant is a relatively recent development.
Edible amaranth is often grown for the plentiful tiny seeds that hang in tassels from the top of the plant after the attractive red flowers fade. The bulk seed is used as a "grain" in porridges or added as a thickener to soups and stews. The seeds are extremely nutritious and protein-packed, with a slightly nutty flavor. You can also use the leaves of amaranth as a leafy vegetable the taste is similar to spinach and it can be used in the same way as many other leafy vegetables, especially in mixed-green salads.
If consumption is the goal, choose annual amaranth varieties marketed as edibles. Nearly all amaranths are edible, including love-lies-bleeding and even the common road-side weedy forms. But those sold as edible varieties are selected for their good seed production and especially tasty leaves.
Amaranth is native to North America and Central America, and is usually planted from seed as soon as the last frost has passed in the spring. If you are eager for early harvest, you can start the seeds indoors as much as eight weeks earlier. If you want to harvest the plants for seeds, it will take about 12 weeks for the plants to reach full maturity. Leaves can be harvested within a few weeks of outdoor planting.
|Common Names||Amaranth, amaranthus, pigweed|
|Plant Type||Herbaceous annual|
|Mature Size||2–5 ft. tall, 1-2 ft. wide|
|Sun Exposure||Full sun, partial shade|
|Soil Type||Moist but well-drained|
|Soil pH||Neutral to acidic|
|Bloom Time||Summer, fall, early winter|
|Flower Color||Red, burgundy, pink, orange, green|
|Hardiness Zones||2-11 (USDA)|
|Native Area||North America, Central America|
Different species of amaranth will produce different qualities of leaves, flowers or seeds. There are over 70 different varieties, so there are plenty of options depending on your goals. Below are a few types to help you pick.
Plants in the gomphrena genus – such as the Gomphrena globosa and Gomphrena haageana, also known as the globe amaranth and the strawberry globe amaranth – are annual flowering ornamentals that sport rounded purple, red, pink, blue, orange or white blossoms. Although native to Central America, gomphrena grows in U.S. Department of Agriculture hardiness zones 7 through 10, making it a fairly good fit for Northern California growers. With proper care, these amaranth plants produce dozens of flowers yearly, making them ideal for bedding and bordering.
Position gomphrena plants in full sunlight. Although the plants tolerate partial shade, full sun makes for more vibrant blossoms. These bedding flowers aren't picky about soil type, but it's best to plant them in well-drained soil during spring. Gomphrena prefers soil with a pH range of about 5.8 to 6.2 and needs about 12 to 18 inches of space.
Fertilize the plant with a balanced, slow-release fertilizer with an N-P-K ratio such as 14-14-14 at planting. Add a water-soluble fertilizer according to the instructions on the label once every few weeks.
Water the gomphrena just enough to keep its root zone saturated. Add water when the topsoil is dry to the touch. Although this plant tolerates the warm weather of the Bay Area well, it flourishes when kept on a regular watering schedule.
Spread a thin layer – about 2 inches – of organic mulch in the gomphrena's bed during summer.
Trim the gomphrena in early spring. Pinch off branch tips to encourage a bushier exterior and pinch off wilted blooms at the stem.
Remove any plants affected by viral disease from the flower bed to prevent spreading. Dig affected plants out by the root, removing the root system completely.
Spray gomphrena with silicone oil NMI-500 or NMI-15 to prevent cutworms, aphids and beetles.
Dan Ketchum has been a professional writer since 2003, with work appearing online and offline in Word Riot, Bazooka Magazine, Anemone Sidecar, Trails and more. Dan's diverse professional background spans from costume design and screenwriting to mixology, manual labor and video game industry publicity.
To cultivate this plant in your garden, wait until the last average frost date for spring has passed before transplanting seedlings. Those who may direct sow have no frost worries in Zones 9 to 11.
Choose a location in full sun. The soil can range in quality from organically-rich loam to clay, provided it drains exceptionally well.
Ideally, the pH is in the range of 6.1 to 7.5, or slightly acidic to the barest hint of alkalinity.
To learn about the characteristics of the earth on your property, conduct a soil test through your local agricultural extension service. Adding compost is one way to increase acidity, while mixing in lime reduces it.
Given globe amaranth’s long taproot, you’ll need to work your garden soil to a crumbly consistency to a depth of at least 12 inches. Add amendments as needed.
Keep the long taproot in mind when container gardening. The taller the plant, the deeper the pot needs to be. Depths of 12 to 24 inches should be adequate.
Sow seeds one-eighth of an inch deep. Scatter a few every four to six inches and cover them lightly with soil.
To transplant thinned out seedlings, cut egg cartons apart if necessary, and bury individual cells or biodegradable containers in their entirety at the same depth as the soil in the cells.
It’s not necessary to fertilize. However, if you routinely treat your garden plants to a nourishing dose, make sure to choose one that’s low in nitrogen, or you may find that you get lots of leaves and few flowers.
Maintain even moisture, but don’t overdo it. Oversaturation can make sprouts prone to “damping off,” a fungal disease that causes them to flop over and die.
When the seedlings have one to two sets of true leaves, thin them out to a spacing of 12 to 18 inches. Good airflow also aids in inhibiting fungal disease.
As plants mature, provide no more than one inch of water per week through a combination of rain and supplemental watering.
Always aim the hose or watering can at the soil, not the leaves, to inhibit fungal growth.
When you see the first flower buds forming, you can pinch them off to encourage bushier growth. Leggy plants may require staking.
Throughout the growing season, periodically deadheading or cutting flowers for arranging serves not only to inhibit leggy growth, but to encourage further blooming.
For best results, cut a portion of a stem, not just a flower head, at a point where it meets another stem, or where two leaves meet.
As a tropical plant, gomphrena loves heat, but requires moisture. And while it withstands drought better than some plants, it thrives best under conditions that mimic the tropics.
You can harvest both the leaves and grains from any amaranth, but if your goal is an edible plant, choose a variety specialized for that. Some types of amaranth are marketed as best for seed production, while others are bred for their attractive, tasty leaves. Regardless of your cultivar, amaranth leaves can be harvested at any point. Small leaves are more tender, but the larger leaves boast a fuller flavor. Large size and heat won’t turn amaranth leaves bitter, as often occurs with other leafy greens, so you can harvest at any point throughout the season.
When harvesting the plant's leaves, make sure to leave the crown intact, as well as some leaves around the top, so the plant can continue to grow. Alternately, you can also cut the whole plant off at ground level when it is between 1 and 2 feet tall. It’s possible that it will resprout for another harvest, though you do risk introducing pests to the open stem.
To harvest amaranth grains, let the plant go all the way to flower. Keep an eye on the flowers as they bloom and begin to die back. Before they all turn brown, cut the flowers off and place them in bags, where they will dry. Shake the bag once they are dry, or knock the seeds loose over a cloth. Rinse away the dried seed “chaff” and enjoy your grain harvest. Amaranth is especially good in a porridge that also contains other grains, like millet and quinoa.