Agapanthus Growing Guide

Agapanthus are attractive, typically violet flowers that are common in warm climates. Ideal for butterfly gardens, these elegant plants produce long, lance-like leaves. Above the foliage, stems up to 3 ft tall, rise. While in the spring and summer lilac or purple globe shaped flowers emerge.

A resilient plant, agapanthus thrives in USDA Zones 6 to 11. Evergreen varieties struggle in colder areas and are best planted in USDA Zones 8 to 11. Alternatively, agapanthus can be grown in pots and treated as houseplants during the colder parts of the year.

A surprisingly hardy plant, some consider the agapanthus to be a weed because it is so resilient. Agapanthus even has some fire resistance thanks to its thick, sap filled leaves which are slow to burn. Many growers, particularly those in hot and arid climates, value the plant’s resilience.

Elegant and resilient, if you want to add an agapanthus plant to your garden, this is your complete guide.

The elegant, globe-like flowers of the agapanthus plant. 

Warning the sap, leaves and rhizomes are toxic to humans and animals. Wear gloves and long sleeves when handling the plants and remember to wash your hands afterwards.

What is Agapanthus?

These popular pollinator plants belong to the Amaryllidaceae plant family. This has 3 subfamilies:

• Allioideae, which includes chives, garlic and onions,
• Amaryllidaceae, including snowdrops and daffodils,
• Agapanthoideae, which comprises of the Agapanthus genus

Interestingly, the name agapanthus comes from the Greek agape meaning love and anthos meaning flower.

To some people these attractive plants lance like foliage resemble lilies. Consequently these plants are also known as Lily of the Nile or African Lily. Native to southern African countries such as South Africa and Swaziland. Today they are naturalized in many countries, including the United States, Mexico, Jamaica, Australia, New Zealand and the UK.

Once established, the plants flower throughout the spring and summer months.

Different Agapanthus Varieties

The most prominent members of the Agapanthus genus are:

•  A. africanus.
• A. praecox,
• A. orientalis,
• A. inapertus

Today there are dozens of cultivated and wild hybrids which are derived largely from these species. While purple flowers remain the most common, some cultivars also flower in shades of blue and white. Depending on the variety the foliage can either be evergreen or deciduous.

A popular flower garden plant, there are a range of different agapanthus varieties to choose from. Some of the most popular include:

• Albus, this variety reliably produces white flowers from August to October. It can be overwintered outdoors in a sunny, sheltered spot. Mature plants reach just over 2 ft in height.
• Midnight Cascade is popular for its dark blue flowers. Like Albus it reaches about 2 ft when mature and can be overwintered outside in a sheltered spot.
• Jacaranda is an early flowering type. From June until August it produces attractive blue flowers. A fully grown specimen measures about 3 ft in height.
• Headbourne Hybrid varieties produce full headed, lilac-blue flowers from August until October. Like other varieties they overwinter in sunny, sheltered spots.
• Black Pantha is a distinctive cultivar, producing black flower buds and dark violet flowers. An evergreen, it is ideal for USDA Zones 8 to 11 and reaches 36 inches in height. Cut flowers last for 2 weeks.
• Galaxy White thrives in USDA Zones 6 to 11. Reaching around 44 inches in height, when in flower it produces attractive white blooms.
• Little Galaxy is prized for its indigo colored, bell shaped flowers which sit on attractive green stems. Traditionally one of the smaller cultivars, reaching around 2 ft, you can now find taller varieties. Little Galaxy is best suited to USDA Zones 6 to 11.

As well as the common purple cultivars, plants also flower in shades of blue and white. 

Typically agapanthus plants are purchased as seedlings or as transplants from plant nurseries and garden stores. While you can grow from seed, I will explain how later, it is a slow process. Plants grown from seed can take up to 3 years to mature before producing any flowers.

In addition to transplants you can also purchase bare roots from nurseries or create your own by taking root divisions from mature plants. Root divisions are clones of parent plants. I will explain how to do this later in the article.

How to Plant

Agapanthus does best in full sun positions. In hot areas a partial shade position, where plants are protected from the heat of the afternoon sun is ideal. The soil should also be well draining. These are drought tolerant plants that struggle if their roots are too wet.

Before planting use a soil test kit to measure the pH level of the soil. It should be between 5.5 and 7.5. Amend soils extremely outside this range before planting. Plants growing in soils slightly outside the ideal pH level range may require a little extra fertilizer.

In cooler areas plant in the shade of a south facing wall or a similarly protected position. This offers some protection from winter weather.

Before planting, allow the soil to warm up to 50 ℉. This gives you time to harden off seedlings and make any necessary soil amendments. Sand, perlite and compost can all be worked into the soil to enrich it and improve drainage.

Planting in the shade of a south facing wall offers some protection from winter temperatures. 

To plant, dig a hole just deep and wide enough to hold the plant’s root ball. To measure the size of the hole, place the plant still in its pot in the hole. It should just fit. If the agapanthus rhizome isn’t in a container, plant roughly 2 inches deep. When you are happy with the size of the hole, remove the plant from the pot and place in the hole. Backfill, firming the soil down as you go and water well.

If you are planting more than one agapanthus plant, space them 18 to 24 inches apart. Mature plants have a spread of up to 36 inches but they like to be a little compact. Planting close together can even help to encourage a better floral display.

After planting apply one inch of water a week to the soil around the plant if it doesn’t rain. Reduce this to half an inch a week when established. Over watering can cause fungal infections or rot.

Planting in Pots

Agapanthus plants do best in compact conditions. Allowing them to become slightly root bound encourages more flowers to form. Consequently, these plants thrive in pots and container gardens. One plant happily flourishes in a pot 8 inches wide and deep. If you want to plant 2 or 3 plants, select a pot 24 to 30 inches wide and deep.

While the pot material doesn’t really matter, planting in a terracotta pot helps to keep the roots warm during the winter months.

Add some well draining potting soil to your chosen container. Mix in a handful of grit or sand to further improve the drainage. Plant so that the top of the root system is about 1.5 to 2 inches below the lip of the pot. You may need to remove or add more soil to get the level right.

When the plant is correctly positioned, fill in the gaps around the roots with more potting soil. Don’t fill all the way to the top of the pot. Keep a little gap between the soil level and the top of the pot. This prevents water from quickly draining away when watering the plants.

Caring for Agapanthus Plants

Regularly weed around the plants. A layer of mulch can help to deter weed growth. It also helps the soil to stay cool and moist.

A popular choice for the mixed flower garden. Irises, daylilies, alliums are all good companion plant choices as is the butterfly bush. Agapanthus also works well when planted in front of taller specimens such as wisteria. Other good companions include:

• Alyssum,
• Birds of Paradise,
• Dianthus,
• Hydrangea,
• Purple Coneflowers.

Water

Once established the agapanthus is a largely drought tolerant plant. Water only when soil is dry. Apply roughly half an inch of water a week. If you are unsure whether to water or not, wait a few more days. It is far better to underwater these specimens than overwater them.

Keep the flowers and foliage as dry as possible to prevent disease. 

Fertilizer

In good conditions a balanced fertilizer, such as 5-5-5 NPK, can be applied once in the spring and again two months later. This keeps the growing plants happy and productive for the entire year. Plants in less favorable positions or poor soil may require more frequent fertilizing.

If you are growing agapanthus in pots, apply a slow release fertilizer in the spring. Alternatively, give growing plants a dose of liquid tomato fertilizer once a year.

For the exact dosage amounts consult the information on the fertilizer label.

To give your plants a further boost, mulch the soil around the plants regularly with compost or well rotted manure.

Overwintering Plants

Resilient evergreen cultivars may survive in warmer zones without the need for protection. In colder zones, once flowering has finished, move pots undercover. Lift plants growing in the ground and replant in pots before moving undercover to a frost free position. The temperature should average between 55 and 60 ℉.

Deciduous varieties should also be lifted and stored undercover. Like evergreen varieties they can either be replanted for the winter or simply stored in newspaper. To do this, lift the rhizomes and brush away any remaining soil. Allow the rhizomes to dry out. Once dry, wrap the rhizomes in newspaper and store in a dark spot where the temperature averages 40 to 50 ℉.

Plants already growing in pots can simply be moved inside. A plant caddy, such as Bright Creations Metal Plant Caddy, makes transporting even the largest plants a simple task.

Pruning Agapanthus Plants

Pruning helps to keep plants healthy and promotes vigorous new growth. It also prevents the plants from outgrowing a space and becoming invasive.

To know when to prune your agapanthus plants, watch the flowers.

Deciduous varieties go dormant in the fall. Once flowering has finished, deadhead the spent blooms to prevent them from setting seed.

Allow the foliage to remain in place until the leaves are all brown and dead. Waiting ensures that photosynthesis can continue and that the rhizomes can store enough energy for winter. Once the foliage starts to die it can be pulled or cut from the plant.

Evergreen cultivars can be pruned and deadheaded once flowering has finished for the year.

Mature specimens may need to be lifted and divided. This rejuvenates plants and also enables you to create divisions.

Regular pruning, deadheading and dividing helps to stop plants from outgrowing their position. 

How to Propagate Agapanthus

Agapanthus can be propagated by either taking root divisions or harvesting seeds. Seeds from hybrids won’t grow true to type and are often disappointing. Additionally, as I have already mentioned, plants grown from seed can take up to 3 years to mature and set flower. Propagating new plants from root division is a lot easier and quicker.

How to Lift and Divide Agapanthus

Healthy plants that produce fresh foliage every year do not need to be divided. If yellow patches appear or leaves begin to die, it could mean that the plant is too congested and needs to be divided. A failure to flower can also be a sign that the root system is too congested.

In general deciduous types should be divided every 6 to 8 years. Evergreens need dividing every 4 to 5 years. Dividing plants is best done in fall or spring. Remember, deciduous cultivars are dormant during the winter so if you transplant in fall, new growth won’t appear until next spring.

Remember to wear work gloves when handling these plants.

To divide, dig a circle 6 to 8 inches deep around the existing clump. As well as digging down, try to dig under the root system. This helps you to lift the plant.

Once fully circled, lift the plants and inspect the roots. Look for spaces between the roots where you can make incisions.

With a sharp knife, cut the tuberous root ball in half. Try to cut between the shoots to avoid damaging new growth. Cut the sections in half again to create 4 new pieces. Each piece should have at least one shoot attached. Agapanthus roots can be difficult to cut, particularly if your tools are blunt. Whetstone is a great investment if you want to keep your tools sharp and effective.

Don’t replant or repot the sections straight away. Allow them to sit outside or in a greenhouse, away from direct sunlight, for 24 hours. During this time the sap stops bleeding and heals over the cut areas. Planting too soon in damp soil can cause wounded areas to rot.

Once the cut areas are healed, replant the divisions.

As well as helping to rejuvenate the plants, making root divisions is a great way to propagate new plants.

Growing from Seed

Allow the flowers to fade and seed heads develop. When they turn brown and the capsules start to burst, cut them away from the plant. Place a paper bag over the seedhead to catch any seeds that ripen before you have a chance to harvest.

Allow spent flowers to remain on the plant. Seed heads soon form. 

After harvesting remove the seeds from the capsules and either sow or store in a labeled paper envelope until you are ready to use.

Seeds can be started undercover at any time of year. Fill a tray with potting soil and moisten. Scatter the seeds as thinly as possible along the top of the soil. Cover the seeds with a fine layer of soil and a thin layer of sand or perlite.

Place the tray in a warm location away from direct sunlight, or in a greenhouse. Continue to keep the soil moist and the seeds warm until germination occurs. This can take anything from a few weeks in ideal conditions to 3 months in colder areas.

Following germination, allow the seedlings to grow on in the tray. The soil should be evenly moist, not wet. When the seedlings have 3 or 4 true leaves, transplant them into 6 to 8 inch pots filled with rich potting soil and sand. This combination ensures that the soil is loose and well draining.

You can leave in the 6 to 8 inch pots or transplant into larger containers when they reach 6 to 8 inches tall. Seeds started in late summer or fall should be kept in pots undercover until the next spring.

Common Pests and Problems

Agapanthus are largely problem free. Larger creatures such as deer and rabbits avoid the plants because of their toxicity.

Powdery mildew, anthracnose and botrytis can be problematic. When watering, only water the soil, keeping the foliage as dry as possible. This, along with adopting other good growing habits such as cleaning your tools, helps to prevent most issues. If an issue does arise, a dose of copper fungicide can be applied.

Root rot can also strike. This is usually caused by growing in wet or boggy soil or over watering the plants. Allow the soil to dry out between waterings. Knowing when to water plants can be tricky. A soil moisture meter, like the Gouven Soil Moisture Meter, can help to simplify the task.

Slugs and snails can also strike. While these don’t kill the plant, they will chew up and destroy the leaves. This article provides a range of easy ways to get rid of slugs in your garden.

Elegant and attractive, these are a colorful addition to the flower garden. 

An elegant addition to the mixed flower bed, where their loose, globe shaped heads provide summer color, agapanthus plants also make great cut flowers. While deciduous cultivars are hardier than evergreen specimens, both are happy in coastal positions where they aren’t deterred by salty air and sea winds. An ideal choice for gravel or rock gardens and dry positions, agapanthus is a trouble free, showy addition to the garden. They will also draw scores of pollinators to the garden.