When to Plant Agapanthus

When to Plant Agapanthus

Agapanthus Growing Guide

Agapanthus plants, also referred to as the African lily or lily of the Nile, are perennials that flower in the summer months. Gardeners prize them for their flamboyant flowers. Although these flowers are usually on the blue to purple spectrum, they also come in pink and white. Considered a landscape staple in regions with warm-winters, these natives of South Africa do well in any sunny spot in the garden, or on the patio in a container, provided that the soil is well drained.

Agapanthus grows in upright clumps from rhizomes, like daylilies. Both deciduous and evergreen, the ribbon-like, or grass-like, leaves are 12-24 inches long and 1-2 inches wide; the flower clusters, borne on sturdy, erect stems held well above the foliage, provide a burst of mid to late summer colour. Although Agapanthus flowers bloom primarily in summer, in frost-free climates they will bloom over a longer period of time.


Agapanthus blooms reliably for almost the entire summer. Once its flowering period has finished, the plant produces seed heads that can be saved and used to create winter flower arrangements. In general, agapanthus plants have varying degrees of cold tolerance; for this reason gardeners living in areas that are colder than H5 (USDA zone 8) should grow agapanthus plants in containers and bring them indoors for the winter.


South Africa averages between 8 and 10 hours of sunlight every day, so you’ll need to place your agapanthus where they will get full sun. It is possible to grow them in light shade but their stems will grow stronger in brighter light. Agapanthus flourishes in moist, fertile, but well-drained soil. With the exception of A. africanus, which likes its soil to be on the acidic side, agapanthus has no pH preference. Good drainage is very important. If the site you’re thinking of still has water puddling 5 to 6 hours after a heavy rain, find somewhere else to plant your agapanthus. If there is no other suitable location, you can improve the drainage by amending the soil with enough organic matter to raise the soil level by 2 to 3 inches. Compost, ground bark, or decomposed manure all good choices, and are nearly ubiquitous. Agapanthus will die (usually by rotting away) in waterlogged soil.


Plant the rhizomes 2 inches deep and 4 to 6 inches apart. Water well, lightly saturating the soil so that it will settle around the rhizomes. Top growth will appear and roots will develop in several weeks. During the spring and summer months, give the plants only enough additional water to keep the soil slightly moist; approximately 1 inch of water a week is a useful gauge. During fall and winter, the soil can be allowed to dry out.

After flowering has concluded for the year, don’t cut the foliage off; leave it in place. The foliage will absorb sunlight, producing nourishment via photosynthesis and building up the rhizome for the following season. You can remove any foliage that turns yellow. In areas where it’s cold, plants should be brought indoors once evening temperatures start to dip to around 5°C.

Related: How to Grow Clematis


In their native South Africa, agapanthus plants experience plentiful rainfall during one season of the year, which encourages growth. This means that agapanthus are quite thirsty, so British gardeners will need to water them well between April and August, particularly if they are in containers. Water sparingly, if at all during the fall and winter.


To keep the blooms going all season long, feed the soil around the plants once a week, or once every two weeks, with a liquid or granular fertilizer that is well balanced, for the duration of the growing season, until the colour of the flowers becomes visible.

Container cultivation

Plant Agapanthus just deep enough to cover the roots, and space them about 8 inches apart. A single plant will fill a 12-inch pot. Use a well drained potting mix, because agapanthus do not tolerate waterlogged soil. During the growing season, only fertilize lightly, too much fertilizer will result in lanky growth. It’s important to choose sturdy pots, such as terracotta, because your plants will be in them for an average of three years before it’s time to divide them. Make sure your pots have nearly straight sides, because pots that are tapered or tall and slender will fall over in a breeze.

When purchasing new agapanthus, make sure you put it in a pot that’s just slightly larger than your plant. Agapanthus plants find it difficult to cope with too much space round their roots. Pot it up once it has filled the pot.

You’ll need to feed and water your agapanthus plants once they begin to grow. They’ll get underway quicker in an unheated greenhouse. Move them to a sheltered place outside in early May.

After flowering, it’s best to remove the seed heads so that your plants put their energy into growing bigger rather than making babies.

Go easy on the watering and feeding in early September and allow the plant to dry out. Place under cover in October. A greenhouse or shed is usually works just fine. Alternatively, you can lay your pot on its side and put it in a sheltered place, such as against the wall of the house. The point is to prevent winter rain and snow from reaching the roots.


Over the years, agapanthus rhizomes form clumps can be easily divided to make new plants. The best time to do this is in the spring and the early part of summer, or in the early part of autumn, after the plants have ceased blooming. Make sure that there are two spots with little shoots in each division. Do not divide the plants too often, because that will decrease the blooming of the original plant. Only divide large clumps every four to six years. Root bound potted plants can be divided every 4-5 years. It’s best to divide after flowering, but it can be done at any time. Use a very sharp knife to cut each clump into sections, complete with roots attached, and pot the sections up. Divisions might not flower until the following year.

It is possible to propagate agapanthus by seed, provided that the seeds are from species not cultivars, because cultivars don’t breed true. Harvest the seedpods in the fall as they turn brown, bring them indoors, and wait for them to split open. Store the seeds in a cool, dry place, and plant them in the spring when the temperature reaches 15°C. During their first winter, these seedlings will need to be protected in a cold frame or an unheated greenhouse. It will take 3-5 years to flower from seed.


It can be disappointing to have agapanthus plants that aren’t blooming. However, learning the most prevalent reasons this happens can help you overcome your disappointment and ensure better future flowering. First off, it’s quite possible that you’re just not being patient. Agapanthus frequently doesn’t flower during its first year. Secondly, the growing conditions might not be quite right.

If your agapanthus isn’t flowering, it might need more sunlight, because agapanthus requires a minimum of six hours of sunlight per day. Agapanthus plants only like a bit of shade in really hot climates, and even then they only want it during the hottest part of the day. If you don’t live in a very hot climate, and agapanthus is in any kind of shade, you need to move it to a location with full sun.

Make sure your plants are growing in soil that is draining well; if it isn’t the plants may rot. Then there’s the problem of overenthusiastic division. Agapanthus actually likes having its roots a little bit crowded, so do not start dividing the plant until it starts to overflow its garden confines, or looks like it’s thinking about bursting out of its container. Splitting up your agapanthus too early can keep it from blooming for two to three years. In general, you shouldn’t divide a youthful agapanthus for a minimum of four or five years. Another issue could be too much or too little water.

Agapanthus plants are vigorous growers that don’t need a large quantity of water once they’ve gotten through their first growing season. Nevertheless, it’s essential to make sure that the plants have sufficient moisture, particularly when the weather is hot and dry. The surest way to figure out if the plants need water is to get your hands in the soil. If the top 3 inches of the soil are dry, the plants need a deep watering. Once winter begins, only water your agapanthus enough to prevent the leaves from wilting. The problem might be that your agapanthus is hungry, and needs fertilizer. Just be careful not to overfeed it.

Feed the plant with a balanced, water-soluble fertilizer for flowering plants every two weeks in the spring, and then decrease the feeding to once a month when it starts to flower. When your agapanthus stops blooming, usually in the early part of fall, stop feeding it altogether. If after attempting all these remedies, the next step is to plant it somewhere else. If it’s in a garden bed, remove it, and put it in a container. If it’s in a container, put it in a sunny garden bed. People sometimes need a change of scene, so that might do the trick for your plant.



If you suspect that your agapanthus has a disease, the first thing you need to do is protect your skin. Agapanthus has a toxic sap that can irritate the skin, and should never be ingested. Always wear gloves, long sleeves, and eye protection when cutting agapanthus stems. Too much moisture is frequently the culprit that brings on the diseases that afflict agapanthus, either from overwatering or inadequate drainage. Gray mould is an ugly fungus that spreads on dying blossoms. The mould requires standing water to grow, so the best way to prevent it is by watering your agapanthus from below and spacing your plants to allow for good air circulation.

If you already have mould, remove the affected portions of the plant and spray the healthy portions thoroughly with neem oil. Anthracnose is another of agapanthus disease that spreads through water. It causes leaves to turn yellow or brown, and to eventually drop. Anthracnose can be treated in the same way as gray mould. Bulb rot and root rot are both agapanthus problems that begin underground.

They manifest above ground as yellow, wilted leaves and occasionally stunted plants. If you dig the plants up, you’ll discover that the roots or rhizomes are decayed and discoloured. If one of your plants is infected with root or bulb rot, there is no saving it. The only thing you can do is to get rid of it to prevent the disease from spreading to other plants. First, cut off the foliage at ground level and seal it inside a plastic bag.

Dig around the roots and lift them out of the ground, taking care to remove as much of the soil around them as you possibly can. Seal the roots in a plastic bag and throw it and the foliage away. Cover the empty spot with a heavy layer of mulch – this will keep sunlight away from any remaining roots and kill them.

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