How to Grow Amaryllis (Hippeastrum) Outdoors| Gardener’s Path

For large, showy spring flowers in USDA Hardiness Zones 9 to 11, you can’t beat the hand-sized, lily-like blooms of amaryllis, Hippeastrum x hybridum.

These tropical beauties can also be forced to bloom indoors during the winter holidays in all growing zones, and then guided through dormancy for blooms in successive years.

In our guide to growing amaryllis indoors, we discuss how to care for potted plants.

In this article, we share all you need to know to grow amaryllis outdoors in the garden or containers, in areas where the weather is conducive to their perennial cultivation.

Here’s what’s in store:

Let’s start with a little background.

An Amaryllis Primer

It all started in the 1700s, when Swedish botanist Charles Linneaus created the Amaryllis genus to classify Amaryllis belladonna, a South African flower with star-shaped blossoms that is now commonly known as the Jersey lily.

In the 1800s, a British botanist named William Herbert described multiple South American star-like blooms as “knight’s stars,” which translates to Hippeastrum in Latin, and created a new genus.

For many years, it was commonplace for both the South African and South American lily-like species, which bear some resemblance to each other, to be classified as Amaryllis.

It wasn’t until the 14th International Botanical Congress of 1987 that botanists decreed that there are indeed two separate genera, and all the South American species were classified as Hippeastrum.

However, old habits die hard, and today Hippeastrum species and hybrids are still commonly known as amaryllis.

By either name, these South and Central American species and the numerous cultivated varieties, are the topic of this guide.

They are truly show-stoppers in the garden, blooming in shades of orange, pink, purple, red, white, and yellow, as well as variegated patterns.

Hybrids vary widely and include Nymphs with multiple layers of petals, Cybisters with especially narrow petals, and Papilios that resemble butterflies.

Bulbs vary in size from 10 to 14 inches in diameter. Each bulb sprouts between one and three flower stems, called scapes, that rise to heights of 12 to 36 inches.

When grown outdoors, these plants naturally bloom in springtime, the ones we enjoy as holiday houseplants have been forced to bloom indoors during the winter months.

The scapes bear four to six lily-like blooms with diameters ranging from four to 10 inches, and flowers bloom in succession for several weeks.

Strappy green leaves sprout beside the scapes, and may reach up to 36 inches in length. After the flowers have finished blooming, these leaves continue to provide nourishment to the bulb until they turn yellow and wither, in time for winter dormancy.

As tender perennials, they can’t tolerate frost but in cooler locations, they can be planted outdoors as annuals and lifted from the ground in fall for overwintering.

Getting Started

To cultivate an amaryllis plant of your own, you’ll need to start from a bulb, seed, divided offset, or bulb section.

The easiest way is to purchase a dormant bulb from a quality purveyor. They vary in size, with the largest typically offering the greatest potential for multiple scapes and flowers per scape.

If you have an existing plant, it is possible to collect seeds after the flowers finish blooming.

However, plants grown from seed may take up to five years to mature and bloom, and those collected from hybrid cultivars will not produce true to the parent plant.

You can learn more about how to cultivate amaryllis from seed in our guide.

Instead of collecting seeds, offset division and bulb resectioning are easily accomplished with mature plants. These techniques will result in clones of the parent plant.

Check out our guide to propagating amaryllis bulbs for full instructions.

How to Grow

If you’re in Zones 9-11, and received a potted bulb as a winter gift, you can enjoy it over the holidays and transplant it to the garden in the spring, where it will revert to its natural tendency to bloom in springtime in a year or so.

You can also purchase dormant bulbs and do your planting in the fall. The bulbs will overwinter in the ground, ready to bloom in the spring.

In cooler regions, you can also grow these flowers as annuals, and either lift the bulbs in fall for replanting the following spring or grow them in containers that can be overwintered in a frost-free location.

If you want your flower to bloom during the winter holidays, keep in mind that it will need to be forced, this will not happen naturally in the Northern Hemisphere.

Outdoor Garden Cultivation

To grow outdoors year-round in the frost-free zones, choose a location with full sun to part shade. Avoid full shade, as it may result in poor flower production.

The soil should be organically-rich and well-draining, with a slightly acidic pH of 6.0 to 6.5.

Choose a sheltered location, as high winds can damage the long flower stalks.

Dormant bulbs can be planted in the spring or fall, and those that have bloomed indoors in the winter can be transplanted in spring with the foliage intact.

Place the bulb neck-deep in the soil, leaving about one-third of the pointed top – and any foliage that may be present – exposed.

Space them 12 to 15 inches apart in odd-numbered groupings for best visual appeal, and to give plants adequate space to bloom.

For spring plantings, keep the soil moist until foliage emerges, and then water sparingly thereafter in the absence of rain to maintain moisture, but avoid waterlogged conditions that can lead to rotting. Once established, plants are drought resistant.

Add an inch or so of mulch around, but not over, the neck of the bulbs, to inhibit weeds and the pests and diseases they may harbor, and aid in moisture retention.

Apply a well-balanced, slow-release fertilizer at the time of planting, such as 6-6-6 or 10-10-10 (NPK). It promotes lush foliage and boosts the nutrition for next year’s flowers.

Container Gardening

In addition to the garden, you may also grow your amaryllis in containers with adequate drainage holes. A shallow depth is suitable, as these plants like to be somewhat rootbound.

Provide a snug fit with a standard pot that has a diameter that allows for only one to two inches of space around the bulb.

Fill the container with a well-draining potting medium to a height that is one inch below the rim, to allow room for watering.

Place it in a full sun to part shade location, and water only when the soil is dry to an inch down.

During very hot, dry weather, keep a close eye on your containers as you don’t want them to dry out completely.

You may move container plants into part shade after they finish blooming, as desired.

Bringing Bulbs Indoors for the Winter

Those in cooler climes who put indoor winter-blooming potted bulbs outdoors for the summer – or are growing these plants as annuals – need to take them inside again before the first frost.

Here’s how:

By summer’s end, the leaves fade to yellow and then turn brown. Cut off any remaining foliage to a height of about an inch, and bring container-grown plants back indoors. Do this before the first frost in cold regions.

Before returning a pot to the house, apply neem oil, a natural fungicide and pesticide, and allow time for the entire container to dry before bringing it inside.

Alternatively, dig the bulb up, discard the old potting soil, and keep it loose, or repot it in a fresh sterile medium.

For plants growing in the garden, you can dig them up, clean off the soil, and either pot them up in sterile medium, or store them loose during dormancy.

Store them potted or loose in a cool, dry location, with a temperature in the range of 45-50°F. Loose bulbs can be gently washed, dried, and stored in a cardboard box.

Do not water at all during the dormancy period.

After 10 to 12 weeks of dormancy, you can pot up loose bulbs and move containers to a 75-80°F location where they can sprout. Alternatively, you can plant them out in the garden after all risk of frost has passed.

Under ideal conditions, you may get a re-bloom in the second and/or successive years.

Growing Tips

• Group by odd-numbers for aesthetically pleasing outdoor displays.
• Keep the soil evenly moist until the first sprout appears. Then water sparingly.
• Mulch outdoor plants to inhibit weeds and aid in moisture retention.
• Use containers that allow for a snug fit and have adequate drainage holes.
• Return bulbs indoors in regions that freeze.

Maintenance

While a bulb by nature contains the food needed to nourish the plant that emerges from it, after the first bloom, it loses vigor.

To give it a nutrient boost, apply a well-balanced, slow-release fertilizer in late winter, like you did when you first planted.

Take care to avoid products with excessive amounts of nitrogen, or you may have too much foliage and too few blossoms.

Late winter is also the time to begin to water the soil around your bulbs. Keep it moist, but not soggy, until you see the first green sprout. Thereafter, water sparingly.

Before the growing season gets underway, remove and replace old mulch. After a year, it deteriorates from a nutritional standpoint, becomes compacted, and may harbor pests and disease.

Amaryllis is phototropic, so staking may be required for the flower stalks. If you do this, be careful not to pierce or damage the bulbs.

As the growing season draws to a close in late summer, and the foliage has withered, remove it from the garden or container, as the debris may harbor pests and disease.

Late summer to early fall is the time to divide large clumps as desired, by digging bulbs up and separating large offsets from the mother to relocate elsewhere.

Managing Pests and Disease

When growing outdoors, keep the garden beds or containers free of weeds that may attract disease-carrying insects that nest in and feed on foliage.

For minor infestations of sap-sucking pests like aphids, mealybugs, spider mites, and thrips, you may be able to rinse them off the foliage with a steady stream of water.

In the case of a large-scale infestation, you might need to apply an insecticidal soap or neem oil.

Fungus gnat larvae feed below the soil and cause foliar deformity. Neem oil is the solution here as well, and it can head off diseases spread by young nymphs, such as wilt and blight.

Another sub-surface pest is the root-knot nematode (Meloidogyne spp.), a type of roundworm. A soil drench of neem oil is an effective treatment.

Slugs and snails turn up when the soil or potting medium is oversaturated. Avoid overwatering and trap them as needed.

The amaryllis borer is a caterpillar that may have a feast both above and below ground. Hand pick it, introduce a caterpillar predator to the garden, or apply neem oil to get rid of this pest.

And finally, grasshoppers may move into the garden to feast on foliage, especially if there are tall weeds nearby.

The lubber variety is fond of amaryllis. Hand pick if possible, or for large infestations, apply Bt, a biological treatment, or a pyrethroid insecticide.

Common diseases include red blotch and soft bulb rot.

Red blotch appears as rusty patches on foliage that often progress to the point of plant collapse. With proper sunlight and watering, it can be avoided.

Commercial growers sometimes apply fungicide or soak affected bulbs in warm water for 30 minutes, but efforts are often futile. Discard entire affected plants.

Southern blight is a fungal infection that can occur in oversaturated soil. Once affected, rotted lesions develop and foliage softens, decays, and dies.

In addition, hungry rodents may eat entire bulbs, or damage them enough to make them vulnerable to infestation and infection.

Deterrents include lining planting holes with loose-weave screening at the time of planting, submerging pots in the ground to form a barrier, and growing above ground in containers.

Best Uses

Where the weather is warm, springtime affords the opportunity to enjoy these flowers in the garden, or to cut them to display in vases indoors.

Plant en masse for armloads, or dot the garden with odd-numbered groupings of three or five for colorful focal points within a larger design.

From beds and borders to containers, both indoors and out, these beautiful flowers make excellent gifts for fellow gardeners, and with so many exciting varieties available, are sure to become favorite in the spring garden.

About Nan Schiller

Nan Schiller is a writer with deep roots in the soil of southeastern Pennsylvania. Her background includes landscape and floral design, a BS in business from Villanova University, and a Certificate of Merit in floral design from Longwood Gardens. An advocate of organic gardening with native plants, she’s always got dirt under her nails and freckles on her nose. With wit and hopefully some wisdom, she shares what she’s learned and is always ready to dig into a new project!