How to Grow Osteospermum

Osteospermum is a colorful, long-lasting flower. In the right conditions they can flower from early summer until the fall. Native to South Africa, these attractive blooms are also known as the Cape or African daisy.

A popular bedding plant, these colorful flowers look great in mixed borders. They are also good pot plants, ideal for planters and container gardens. When in flower an osteospermum attracts scores of pollinators to the garden. At their best with a regular drop of water and some light pruning, the osteospermum brings color and interest to any outdoor space. Here is your guide to growing osteospermum.

A large flowering plant, the African daisy is a popular plant with both gardeners and pollinators. 

Different Varieties of Osteospermum

The vast majority of osteospermum cultivars are classed as tender perennials in USDA Zones 9 and warmer. In cooler areas they are best grown as annuals. A member of the asteraceae or daisy family, most varieties range from 8 to 24 inches in height.

As well as tender varieties you will also find half hardy cultivars. Half hardy osteospermum plants are a better choice for growers in cooler areas. While these flowers are typically grown as annuals, planting in pots enables you to take the plants undercover in the fall and overwinter. African daisy flowers come in a range of eye-catching colors, including shades of purple, white, yellow and orange.

One of the most popular cultivars is the 4D series. These tall plants, reaching about 14 inches, are primarily grown for the flowers which have tufted, fluffy centers. Once fully open the flowers remain open all day.

Lemon Symphony is another tall cultivar. As the name suggests its lemon yellow flowers are a striking sight in the middle of a flower bed. At the heart of the flower a purple center and orange eye provide interesting contrast.

Passion Mix is a compact cultivar which comes in a range of colors. But whatever color the flower is, be it purple, pink, white or rose, the center of a Passion Mix cultivar is always blue. This cultivar is pleasingly easy to grow from seed and is also heat tolerant.

Sideshow Copper Apricot is a striking plant, producing pale apricot flowers and purple centers.

African daisies flower in a range of colorful combinations.

Sunny Mary is prized for its masses of purple-pink flowers which bloom throughout the summer. Thriving in mixed sunny borders it is also good for cut flowers.

Osteospermum Ecklonis is a white flowering variety. The back of the petals are deep blue, matching the center of the plant. Sunny Phili is another popular white flowering variety. Its petals have a purple underside. This tender cultivar is best grown as an annual.

Finally, Osteospermum jucundum var. compactum is a good ground cover choice where its low growth habit is useful for suppressing weed growth. This variety also produces masses of narrow green foliage and purple flowers.

While you can grow some varieties from seed, African daisy plants are typically purchased from garden centers and plant nurseries as young or plug plants, ready for planting out into the garden.

Growing from Seed

As we have already noted, these plants are typically purchased as young or plug plants. However, you can grow some varieties of osteospermum from seed. An easier propagation method is to grow new, heavy flowering plants from cuttings. I will explain how to do this later in the article.

To grow from seed, fill a seed tray with fresh potting soil. Moisten the soil before sprinkling the seeds over the top. There is no need to cover the seeds with more soil. They need lots of light to germinate.

Place the tray in a propagator or cover the top. Some seed trays, such as ANGTUO Plant Germination Starter Kits come with a fitted humidity dome. Otherwise you can place the trays in a clear plastic bag. African daisy seeds germinate best in a cool, light location. Unlike other seeds a high temperature is not necessary.

Seeds usually emerge within 2 weeks. Once the seedlings are 3 inches tall, transplant them into individual pots. Continue to grow the seedlings on undercover until the last frost has passed. Harden off the seedlings before transplanting into the garden.

How to Plant Osteospermum

Osteospermum plants do best in full sun positions. While they flower in partial sun, flowering may not be as profuse. The perfect position should also have some protection from the wind. The wind can lower the air temperature, this is not ideal for plants such as osteospermum which like to be warm.

These colorful plants flower more profusely if planted in a sunny spot. 

The soil should be well draining and, ideally, slightly acidic. Use a soil test kit before planting to work out whether you need to amend your soil. If your soil is overly alkaline in nature, there are a number of ways to make it more acidic.

Work in compost or organic matter to enrich the soil. You can also work in some sand or grit to help improve drainage. This is best done when hardening off your plants.

Finally, work in some organic fertilizer before planting.

If you are planting in pots, your chosen container should be about 11 inches wide. As well as being large enough to hold the fully grown plant it should also have drainage holes in the bottom. Fill the pot with fresh potting soil and work in some organic fertilizer.

Planting is best done in the spring. In warmer regions, especially those that enjoy mild winters, you can also plant in the fall. But be careful, the plants won’t survive exposure to temperatures below 23 ℉.

To plant, make a hole in the soil large enough to hold the plant. When placed in the hole the osteospermum should sit level with the soil. If you are planting in poorly draining soil, elevate the plant slightly so that the top of the root system sits just above soil level. This encourages excess water to drain away from the plant, helping to prevent issues such as root rot.

Gently firm down the soil around the plant and water well. If you are planting more than one osteospermum, space the plants 12 to 16 inches apart. The exact spacing depends on the height and spread of the variety you are growing. This information is normally provided on the plant information label.

Space the plants out correctly. They soon grow and fill any gaps in your border. 

How to Care for Osteospermum

Once planted, these plants require a little regular care to ensure an abundant flowering display.

As your plants develop, pinch out new growth two or three times a year. This should be done during the early part of the growing season. Pinching out encourages a sturdy stem and bushy plant to develop.

Water

Water the plants regularly. The soil should be kept evenly moist. Allowing the soil to dry out can cause growth to slow. It also deters flowering and may cause plants to become dormant.

If you find it difficult to know when to water, why not invest in a soil moisture meter? These useful devices, such as the Gouevn Soil Moisture Meter, provide an accurate and easy to read way to monitor the moisture content in your soil.

Keep the soil evenly moist to encourage more flowers to form.

Regularly watering is particularly important during dry spells. Don’t allow the soil to dry out. If it doesn’t rain, plants require about 1 inch of water a week. In warmer areas they may require more than this.

Fertilizer

Fertilize the plants once a week during the growing season with a general purpose plant food. This helps to promote and prolong flowering. You can also use a diluted fermented weed tea once a month. The solution should be diluted to a tenth of its initial strength.

Pruning your Plants

Deadhead, or cut away, any wilting or spent flowers. This encourages new blooms to form. It also helps to keep your plants healthy.

Cut back plants if they become overly tall or leggy. This is common if you have planted the flowers in a shady spot where they have to stretch to reach the sun. Cut back plants, if necessary, in early spring just before or as new growth emerges. Cut all the stems back to about 4 inches above the soil. Following this, topress the soil around the plant with some rich compost.

You can also cut back the hardy or half hardy cultivars in late fall. This is recommended if you are overwintering the plants.

Regularly prune and deadhead your plants to encourage more flowers to form.

How to Overwinter an African Daisy

In cooler areas plants require some form of protection to help them survive the winter months. Plants in pots can simply be moved inside, to a greenhouse or a conservatory, for the winter months. Wait until the last frost has passed and the temperatures have started to warm up before returning them to their usual position.

If you have chosen to plant your osteospermum flowers in the ground or a planter, they can be covered with a horticultural fleece. Cut back the plants before covering. Remove covers in the spring once the last frost date has passed.

How to Propagate new Plants

The easiest way to get lots of new osteospermum plants is to take cuttings either in spring or late summer. Use sharp scissors to take cuttings from the tip of non-flowering, healthy shoots.

Remove the foliage from the lower half of the cutting and dip the cut end in rooting hormone. Plant the cutting in a small pot filled with moist, well draining compost. You can also plant several cuttings around the edge of a slightly larger pot.

Place the cuttings in a light position and continue to keep the soil moist. Pot on once roots form and new growth is visible.

Source: https://www.youtube.com/watch?v=QzEvUa6V-zE 

Gardeners in warmer areas, or those growing plants in pots or planters, can propagate their osteospermum by lifting the plant and dividing the clump. To do this, dig a circle all around the plant, this enables you to dig under the plant and lift as much of it and the root system in one go.

After lifting the plant, use a sharp knife or the edge of your shovel to split the root system into two or three healthy clumps. Shake off any excess soil and remove any dead growth. Replant the divisions in favorable positions or pots.

Allow plants at least 3 of continuous years of growth before attempting to divide them. Divisions are best made either in the spring or the fall. Before dividing, cut back the plant. This helps to reduce the chances of shock affecting your new plants.

Common Osteospermum Problems

If planted in a favorable position and correctly cared for this is a pleasingly problem free plant.

The foliage can fall victim to infestations of aphids. Regularly check the leaves for signs of these common pests. Treat affected leaves with insecticidal soap, which is easy to make at home. Infestations may require two or three treatments spaced out over the course of 6 weeks to fully cure the infestation.

Downy mildew can form if the plants are not watered regularly or the soil is allowed to dry out. This problem can cause foliage to become spotted. Keeping the foliage as dry as possible when watering and correctly spacing out the plants, so that air can freely circulate, helps to prevent the problem.

Watering the soil, keeping the plants as dry as possible helps to prevent downy mildew.

A popular member of the flower garden, osteospermum flowers look particularly effective when planted alongside petunias, verbena, ageratum, dusty miller, zinnias and other daisies. If you want to use the colorful blooms in a cut flower display, cut them as soon as they open.

Colorful, long lasting and relatively easy to care for it is easy to see why the osteospermum is such a popular member of the flower garden.