How to Plant, Grow, and Care for Gomphrena

One of my favorite aspects of flowers is the wide variety of shapes and colors they come in. Round flowers like daisies and coneflowers have a classic shape, and spikes like snapdragons and delphinium add height to the garden and bouquets. And gomphrena’s spherical blooms add a unique element to gardens and bouquets.

Also known as globe amaranth, gomphrena produces many small, round flowers that are beautiful when fresh and dried. They come in a wide range of colors, so you can likely find one you’ll love. These annuals can also tolerate high temperatures, making them great flowers for the summer garden.

The plants are often grown for cutting flowers since they hold up well when fresh and dried. Gardeners also plant them for their long bloom time and ability to attract pollinators.

Characteristics

Gomphrena produces stiff stems that grow in a branching pattern. The stems are covered with  oblong leaves covered with short, fuzzy hairs. A small, spherical flower appears at the top of each stem.

The round flowers are made up of stiff, papery bracts that retain their shape and texture over time. The blooms come in many colors, including pink, lilac, orange, white, and red.

Native Range

Gomphrena is native to Central America and northern portions of South America. It grows year-round in warm regions, but you can grow it as an annual in cooler climates.

Planting

This warm-season annual is an easy-to-grow plant provided that you grow it at the right time of the year. Since it’s sensitive to cold temperatures, you should wait until the last frost has passed before planting it outdoors. You can grow gomphrena by starting seeds indoors and transplanting the seedlings or purchasing seedlings from a nursery.

Starting From Seed

If you want to give your plants a jumpstart or want reliable germination, starting seeds indoors is your best option. Sowing seeds indoors allows you to provide the optimal temperature, light, and moisture, leading to excellent germination rates. Once the seedlings are a few inches tall, you can transplant them outdoors.

Gomphrena takes between six and eight weeks to go from a seed to a seedling that’s large enough to plant, so don’t start your seeds any earlier than eight weeks before your last spring frost date.

Start by filling seed starting trays with a well-draining seedling mix, gently pressing the mix into the cells. Make a small indentation in each cell, about an eighth of an inch deep. Place one to two seeds per cell, then gently cover with soil mix or vermiculite.

Gomphrena seeds are tiny, so it’s sometimes difficult to separate the seeds. While it’s fine to plant multiple seeds per cell and thin out the extras, you can also use a toothpick to move individual seeds into the cells. Just moisten the end of the toothpick, touch it to a seed, then move the seed to the container.

Once your seeds are in their containers, water well.  You gently water the tops of the cells using a watering can or bottom water by placing the trays on a bottom tray filled with about half an inch of water. Set the trays somewhere between 70-80°F (21-29°C). Use a heat mat if necessary.

The seedlings should emerge within one to two weeks. As soon as you see sprouts, move the plants to a location that receives ten to twelve hours of bright light. Using a grow light can help you provide the right type of lighting if you don’t have access to a greenhouse or sunroom.

Continue to keep the soil moist as the seedlings grow. If you planted multiple seeds per cell, thin to one to two seedlings when the plants have their first set of true leaves. You can begin to harden off the plants after your last spring frost.

Transplanting

Since gomphrena isn’t a great candidate for direct sowing, transplanting is the best growing method. You can start with seedlings you’ve grown indoors or look for plants at a local garden center or nursery. No matter where you obtain your plants, wait until the nights remain above 40°F (4°C) before setting them outdoors.

Although gomphrena grows in a branching form, it doesn’t mind tight spacing. The plants grow against each other, with the stems supporting one another and encouraging upright growth. Therefore, spacing the plants 6-12 inches apart is ideal.

Mark out where you’ll place each gomphrena plant, then dig holes the size of the seedlings’ root balls. Place a plant in each hole, cover the top of the root ball with soil, then water well.

How to Grow and Care for Gomphrena

Fortunately, gomphrena is easy to care for, as long as you plant it in the right area and provide the proper care. Remember these requirements to keep your plants healthy.

Light

Gomphrena thrives in full sun. Providing it with at least ten hours of daily light will lead to healthy plants filled with flowers. However, you can plant the plants in an area that receives a few hours of morning or afternoon shade. Just don’t be surprised if the plants produce fewer flowers than those growing in full sun.

Water

These annuals can tolerate a light drought once they’re established, but recent transplants require moist soil to settle into their new homes. Aim to keep the water moderately moist in the first few weeks following transplanting.

Watering two to four times a week is often ideal, but checking the top two inches of soil is the best way to determine whether or not you should water. If the soil feels dry, it’s time to water. However, if the soil feels moist, wait to water.

Once the plants have developed more robust root systems, you can reduce the amount of water you give them. Watering the plants deeply one to two times a week is often sufficient and preferred over watering them lightly each day.

Gomphrena isn’t super prone to fungal diseases, but I still recommend watering near the base of the plants to keep the leaves dry. You can use a drip irrigation system or simply water the ground with a hose or watering can.

Soil

Gomphrena tolerates a range of soil types, but it performs best in well-draining soil with a pH between 6.0 and 7.0. If your soil is heavy clay or compacted, consider aerating the soil with a digging fork or shovel. Adding compost prior to planting will also help limit compaction and provide a habitat for beneficial microbes.

You can also grow gomphrena in raised beds or containers. If you’re using a soilless potting mix, select one that provides good drainage and retains moisture for at least a day.

Temperature and Humidity

This annual thrives in warm temperatures and doesn’t mind excessive heat. It grows best when daytime highs are between 70-90°F (21-32°C), but can tolerate temperatures above 100°F (38°C).

Since it’s not frost-hardy, wait until all danger of frost has passed before planting. Ideally, wait until nighttime temperatures remain above 40°F (4°C).

Gomphrena handles high humidity without much issue and is rarely affected by fungal diseases.

Fertilizing

Gomphrena can often grow well even if you don’t add fertilizer. Adding a half-inch of compost before planting will often provide the plants with all the nutrients they need.

If you suspect your soil is lacking essential nutrients, you can conduct a soil test to identify the specific deficiencies and apply the missing nutrients. Once you address these deficiencies, you won’t need to fertilize your gomphrena as it grows. 

Maintenance

Gomphrena is pretty low-maintenance once it’s established. The plants don’t require any type of support and rarely require pruning.

However, deadheading old flowers will keep the plants tidy and encourage them to produce new blooms. If you see a flower that has grown into an oblong shape with faded color, remove it from the plant. You can use a pair of clippers to easily snip the bloom from the stem.

Harvesting

Gomphrena flowers will mature about 100 days after you plant the seeds. Look for round flower heads on rigid stems. The flowers at the top of the plants will mature first, followed by the blooms on the side shoots.

You can harvest smaller blooms with less rigid stems, but these flowers won’t hold up in a vase as well as their more mature counterparts. To harvest, cut the stem near the base of the plant while leaving a few side shoots to mature. Strip the leaves near the bottom of the stem, then place the stems in water.

If you want to dry gomphrena, harvest it in a similar manner. After you harvest, hang the stems upside down in a dry location with good circulation. You can bundle a few stems together, but don’t group them so tightly that air can’t make its way between the stems. Depending on the temperature and humidity, the flowers should be dry in one to three weeks.

Common Issues

Gomphrena is resistant to most pests and diseases. However, a few issues may pop up, especially when there are less-than-ideal growing conditions.

Root Rot

Excessively wet or poorly draining soil can lead to root rot. This occurs when fungal infections take hold of the roots and prevent them from taking up water and nutrients. Fortunately, preventing root rot is easy.

Avoid overwatering and plant gomphrena in well-drained areas. Don’t plant these flowers in low-lying areas or those with compacted soil.

Leaf Spot

In very humid conditions, gomphrena may develop occasional leaf spots. The spots normally appear pink or tan, making them stand out from the green foliage. These spots may be caused by numerous pathogens, but Alternaria gomphrenae commonly infects these plants. If you notice unusual spots, remove and dispose of the affected leaves.

Since leaf spots are more likely to occur in moist, stagnant air, allow proper spacing between plants. This will encourage good airflow and help prevent the disease.

Aphids

Aphids are tiny insects that may not seem like a threat when you first spot them. However, these pests pierce gomphrena leaves and then drink their sap. When lots of the pests feed at once, the plant becomes weakened.

Since a few aphids aren’t a problem, you can often rely on natural predators to help keep their populations low. Insects like ladybugs, parasitic wasps, and lacewings all feed on aphids. Planting a range of flowering plants and avoiding broad-spectrum pesticides will help keep these good bugs around.

Sometimes aphids get out of control, even if you have a healthy environment. If you notice your plants are covered by pests, treat them. You can sometimes remove aphids with a steady stream of water, but you may need to spray them with insecticidal soap or neem oil. Either treatment is best carried out in the morning before pollinators are active, while foliage can dry as the sun rises.

Frequently Asked Questions