Gadenin日本語Get the appThey want damp shade, not the sunny spot
Nearly everyone puts a primula in the brightest place they have, because it was bought in full flower and full flower looks like a sun plant. It is not. Primulas are woodland and streamside plants, and what they are built for is the light that reaches the floor of a wood in spring, before the trees are in leaf: bright, open, and shaded again by the time real heat arrives. A position that gets morning sun and shade from midday onwards is close to ideal. Full afternoon sun in summer scorches the leaf edges brown, halves the size of the plant and, in a pot, kills it outright inside a fortnight.
The other half of the requirement is moisture. Primulas have shallow, fibrous roots sitting in the top four inches (10 cm) of soil, and that layer is exactly the layer that dries first. Soil that stays evenly damp without standing water suits them; dry soil under a hedge or against a house wall does not, however shaded it is. If the only shade you have is dry shade, dig in two or three inches (5 to 8 cm) of leaf mold or garden compost before planting and mulch every year, or grow them in pots you can water instead.
Temperature matters more than people expect. Primulas grow actively at 40F to 65F (4C to 18C) and stop above about 75F (24C). A plant that sits still through high summer and makes no new leaves is not sick; it is waiting, and it starts again as soon as nights cool.
Watering: little and often is wrong, even for a bog plant
The mistake with primulas is watering the surface. Because the leaves flag quickly, people give a small splash daily, which wets the crown and the top inch and leaves the root ball dry underneath. Water thoroughly instead, until it runs from the base of the pot or until the soil is wet a hand's depth down, then leave it until the top inch (2.5 cm) feels dry to the finger. In a shaded border in spring that may be once a week; in a pot in a warm dry spell it may be daily.
Water into the soil around the plant rather than over the middle of it. The crown, where the leaf stalks all meet, is the part that rots, and water sitting in that cup overnight in cool weather is how crown rot starts. This matters most for the pot plants sold in flower, which have a dense rosette and compost that holds water hard.
A wilted primula in the middle of a warm day that is firm and upright again by evening was short of water for an hour and has taken no harm. A primula that is limp in the cool of the morning has either dried out completely or has lost its roots, and those two look identical from above. Lift it and look before you water again.
| Situation | How often to water | What to check |
|---|---|---|
| Pot plant in flower, indoors | Every two or three days | Compost damp a finger deep; empty the saucer |
| Pot outdoors, spring | Twice a week, more in wind | Lift the pot; a dry one is noticeably light |
| Planted in shade, first season | A good soak weekly in dry spells | Keep the original root ball damp, not just the soil round it |
| Established clump in damp shade | Only in a drought | Leaf edges browning inwards means it is dry |
| High summer, plant resting | Enough to stop it drying out, no more | No new leaves is normal; yellowing lower leaves is not |
Feeding, and why less is better
In open ground with an annual mulch, primulas need no fertilizer at all. The mulch is the feed: an inch (2.5 cm) of leaf mold or garden compost spread around the clumps after flowering feeds them, keeps the shallow roots cool and holds the moisture they want. Keep the mulch off the crown itself so it does not sit wet against the leaf bases.
In pots they do need feeding, because a plant bought in flower has usually had all it is going to get. A balanced liquid feed at half strength every two weeks from the start of growth until flowering finishes is plenty. Heavy nitrogen gives large soft leaves that flop, hide the flowers and attract every slug in the garden. If a potted plant is all leaf and few flowers, that is almost always the reason.
Deadhead as the flowers go over, taking the whole flower stalk down to the base rather than snapping off the top. Left alone the plant puts its energy into seed pods, and although self sown seedlings are welcome in a shady border, a plant carrying a full crop of seed will not flower as strongly the following spring.
Write down where each clump is planted and the date it started flowering. Primulas disappear completely for part of the year in some gardens, and a map saves you putting a fork through them; the flowering dates tell you within two seasons which corners of your garden are genuinely cooler.
Do not throw away the pot plant when it stops flowering
Primulas in flower are sold as seasonal color and most of them are thrown out when the display ends. That is a waste, because the great majority of them are perfectly hardy perennials that were simply forced into flower early under glass. Planted out, the same plant will settle down, flower on its natural schedule the following spring and go on for years, getting steadily larger.
Do it as soon as the last flowers fade, while the plant is still in growth and the soil is workable. Choose a shaded spot with soil that does not bake, knock the plant out of its pot and tease the outer roots loose, because forced plants are usually pot bound and the roots will otherwise stay in the shape of the pot. Plant at the same depth it was growing, with the crown level with the soil surface and never buried, then water it in and keep it damp for the first month.
Expect it to look unimpressive for the rest of that first year. It is replacing a forced root system with a real one. The test is the following spring, when it will come into flower later than it did in the shop and last far longer outdoors in cool weather than it ever did on a windowsill.
Divide the clumps as soon as flowering ends
An established primula builds up into a congested clump of crowns pressed together, and once that happens the flowers get smaller and the middle of the clump dies out. Splitting it every two or three years is the single job that keeps primulas going, and the time to do it is straight after flowering, not in autumn and not in the following spring. Doing it then gives the divisions a full season of cool, damp growing weather to root before they are asked to do anything.
Lift the whole clump with a fork, shake off enough soil to see the structure, and you will find it is made of separate crowns, each with its own fan of leaves and its own roots. Pull them apart with your hands; they come away easily and a knife is rarely needed. Discard the woody, leafless center and keep the young outer pieces.
Replant immediately at the original depth, one crown per position, a hand's width apart, and water them in. Trimming the largest leaves back by half reduces water loss while the roots re establish. Divisions wilt for a few days and then pick up; ones left lying about with bare roots for an hour on a drying day often do not.
- Lift the clump after the last flower fades Push a fork in well outside the leaves and lever the whole clump up in one piece. Work on a dull day or in the evening if you can, so the roots are not drying while you work.
- Pull it apart into single crowns Shake or wash off soil until you can see individual rosettes. Separate them by hand, each with roots attached. Throw away the old hard center, which will never flower well again.
- Replant at once and water in Set each division at its original depth with the crown at soil level, firm gently, water thoroughly and mulch around but not over the crown. Keep them damp for the next month.