Gadenin日本語Get the appWhen to plant and what a good plant looks like
Plant out after the last frost, once the soil has warmed and nights are reliably above about 45F (7C). Osteospermum tolerates a light frost better than most bedding plants and can go out a little earlier than the tender annuals, but a plant set into cold wet soil sulks for weeks and is far more likely to rot at the base than one planted a fortnight later into warm ground. If you are working with plants raised under cover, harden them off over seven to ten days, moving them outside for progressively longer and bringing them in on cold nights.
Choose short, dense, many-stemmed plants over tall ones in full flower. A plant already carrying open daisies at the top of a single stretched stem has been grown fast and will keep that shape; it will never make the low branching mound you want. The best plant in the tray is usually the stocky one with plenty of leaves at the base and buds not yet open. Check the underside of the top leaves for aphids before you buy, and slide one out of its pot to see roots that are white and working rather than a solid brown spiral.
If you are planting the young plants you rooted from cuttings the previous late summer, treat them exactly the same way. They will have spent the winter under cover and will be softer than nursery stock, so harden them off properly and do not rush them into cold ground.
Position and soil preparation
Pick the sunniest spot you have with the freest drainage. Six hours of direct sun is the minimum and eight or more gives noticeably better plants. Because the flowers shut in low light, a partly shaded position costs you twice: fewer buds, and fewer of those buds open at any given moment. A slope, a raised bed, a gravel garden or the edge of a path are all ideal; the low corner where puddles sit after rain is the one place it will not survive.
Osteospermum does not want a rich bed. Over-improved soil full of compost gives you a large soft plant with few flowers, and it also holds the winter wet that rots the crown. On heavy clay, fork in coarse grit or sharp sand across the whole planting area rather than dropping a handful into each hole, which only creates a sump that fills with water. On sandy or stony ground, plant it as it is and do nothing.
For containers, use a free-draining potting mix with about a quarter grit or perlite by volume. Pick a pot wide rather than deep, with open drainage holes, and use terracotta over plastic if you have the choice because it dries between waterings. A single plant is comfortable in a pot around ten inches (25 cm) across; crowding three into the same pot gives a good first month and a congested, mildew-prone mess by midsummer.
| Item | Target | Why it matters |
|---|---|---|
| Sun | Six hours minimum, eight or more preferred | Sets bud numbers and how long flowers stay open |
| Soil temperature at planting | Warm, nights above 45F (7C) | Cold wet soil causes sulking and crown rot |
| Spacing in beds | Twelve to eighteen inches (30 to 45 cm) | Airflow prevents downy mildew and gray mold |
| Planting depth | Crown level or slightly proud of the surface | Keeps the stem bases out of standing water |
| Container size | Around ten inches (25 cm) across per plant | Room to branch without congestion |
| Container mix | Free-draining, about a quarter grit or perlite | Sharp drainage is more important than fertility |
| Feed at planting | None, or a single light balanced dose | Nitrogen produces leaves at the expense of flowers |
Putting the plant in the ground
The planting itself is quick, and the two details that matter are depth and firming. Everything else is ordinary.
Work on a dull day or in the evening rather than in hot midday sun, so the plant is not trying to establish and cope with heat at the same time.
- Water the plant an hour before Soak the plant in its pot and let it drain. A dry rootball repels water once it is in the ground and the plant can sit thirsty in damp soil for days. Do not plant a bone-dry rootball.
- Dig a hole slightly wider than the rootball Make it a little wider than the pot but no deeper. Loosen the sides if the soil is compacted so roots can get out sideways, and do not add compost or fertilizer to the bottom of the hole.
- Tease the roots free If the roots are circling the outside of the rootball, pull the outer ones loose with your fingers and tease the bottom apart. A rootbound plant put in untouched will keep growing in a circle and stay small all season.
- Set the crown level or slightly high The point where the stems meet the roots should sit at the soil surface or half an inch (1 cm) above it. Planting deep, so soil covers the stem bases, is the most common cause of rot. On heavy ground, deliberately plant proud and mound soil up to the sides.
- Backfill and firm gently Fill with the soil you took out, firming with your fingers rather than treading it down. You want no large air pockets around the roots but not compacted ground either, since compaction defeats the drainage you are relying on.
- Water in and then hold back Water thoroughly once to settle the soil around the roots. Then let the surface dry before watering again. Keeping a newly planted African daisy constantly damp is how you get a rotted one in three weeks.
- Pinch the tips Once the plant has taken and is putting out new growth, usually after about two weeks, pinch an inch (2.5 cm) off each shoot tip. You lose the first flowers and gain a branched plant with several times the bud count.
The first month
Water newly planted African daisies deeply once or twice a week for the first three or four weeks rather than a little every day. Deep infrequent watering pulls the roots down; light frequent watering keeps them at the surface where they dry out and where the crown stays permanently damp. After a month in open ground, a plant should need water only in a genuine drought.
Do not feed at planting and do not feed for the first few weeks. The plant is making roots, and nitrogen at this stage produces top growth it cannot yet support. If you feed at all, start once the plant is visibly growing away and use a balanced liquid feed every two to three weeks, or a high-potash one if you want to push flowering.
Keep mulch away from the stems. A gravel mulch suits this plant well, keeps the root zone cool and steady, and helps keep the crown dry, but pull any mulch back an inch or two (a few centimeters) from the base. Watch the shoot tips for aphids through the first weeks, since soft new growth on a freshly planted specimen is exactly what they look for.
If the plant wilts in the afternoon of a hot day but is firm again by morning, it is fine. Wilting that is still there first thing in the morning means either a genuinely dry rootball or roots that have started to rot.
What to record at planting
Sketch where each plant went rather than describing it. Next spring you will not remember which end of the bed you meant, and position is the variable that decides how well this plant performs. Alongside each position, write the number of hours of direct sun you actually observed, checked at three or four points through one clear day.
Note the planting date and the state of the plant when it went in: stocky or stretched, in bud or in flower, home-rooted cutting or bought plant. Compare that against how each one looked at midsummer. It takes one season to convince yourself that the stocky plant with no open flowers was the better buy.
Record what you did to the soil in each spot and whether anything rotted there. Drainage problems are invisible until something dies in them, and a note saying that the plants along the low edge of the bed all collapsed in a wet spell is what stops you replanting the same place next year.