Gadenin日本語Get the appThe shape of the year
Japanese anemone runs on a back-to-front calendar compared with most border perennials. It emerges late, spends the whole first half of the year building leaves and doing nothing you would call ornamental, and then delivers everything from late summer until frost. Your work is loaded into the opposite end of the year from its display.
Almost all of it is done in spring: clear the crown, decide where the colony is allowed to be, and put support in before the stems get tall. Summer is watering. Autumn is enjoying it. Winter is nothing at all.
The table below is the whole year on one page. Everything after it is detail.
| Season | What the plant is doing | What you do |
|---|---|---|
| Late winter | Dormant, crown still below ground | Clear old stems and debris, take root cuttings |
| Early spring | Shoots breaking, new rosettes visible away from the clump | Cut the containment edge, divide or lift offsets, slug protection |
| Mid to late spring | Leaf clump building, no stems yet | Mulch, set supports at about 12 in (30 cm) of growth |
| Early summer | Clump filling out, flower stems extending | Water in dry spells, check tips for aphids |
| Midsummer | Flower stems tall, buds forming | Do not let the soil dry out, this decides the display |
| Late summer to mid autumn | Flowering, buds opening in succession | Light deadheading only, no stem cutting |
| Late autumn | Seed heads, foliage fading after frost | Cut frosted stems, leave green basal leaves |
| Winter | Fully dormant | Nothing, keep the crown clear of wet debris |
Late winter and early spring: the work that pays
Start by clearing. Pull off any stems left standing over winter, rake the fallen leaves and dead material off the crown, and bag anything that showed straight-edged brown wedges last season rather than composting it. A crown sitting under a wet mat of debris is the one thing likely to rot it, and the debris is where slugs have spent the winter.
Then make the annual decision about size. In early spring you can see exactly where the colony has got to, because the new leaf rosettes stand out clearly on bare soil, including the ones that have appeared well away from the parent clump. Push a spade in vertically along the line you want to hold, all the way round, and lift out everything beyond it. Pull each stray crown out with its horizontal root attached rather than snapping it, because a snapped root left in the soil regrows.
This is also the moment for propagation. The offsets you have just lifted are complete young plants and can be potted or replanted immediately. If you want more, root cuttings taken in late winter, before growth restarts, root readily in a cold frame.
Finally, put slug protection down before the first leaves appear, not after the first holes. The vulnerable window is only a few weeks long, but it is the same few weeks every year.
Late spring to midsummer: the quiet build-up
Nothing much appears to happen through this period, and that is exactly when the two jobs that decide the autumn get done: mulching and support.
- Mulch while the soil is still moist Spread two inches (5 cm) of compost or bark over the whole colony in mid spring, keeping it an inch clear of the crowns. Mulch applied to damp soil holds that moisture into summer. Mulch applied to soil that has already dried out in midsummer keeps the rain out and makes things worse.
- Set supports at 12 inches (30 cm) of growth When the clump is about a foot tall, put ring supports, a grid or brushwood over it so the stems grow up through. Position the support so it will finish about a third of the way up the eventual stem height, which for this plant means three to four feet (90 to 120 cm) total. Do this now and it disappears under the foliage.
- Start watching soil moisture from midsummer From midsummer the plant is building flower stems, and dry soil at this point cuts the number of flowers you get in autumn. Check under the mulch with a finger weekly. If it is dry two inches (5 cm) down, give the clump a long slow soak rather than a light sprinkle.
- Check the stem tips for aphids Black aphids build up on the softest growth in early summer. A ten-second look each week catches them early, and a jet of water usually settles it. Low numbers are not worth treating.
- Do not cut anything back There is no summer pruning, pinching or trimming for this plant. Every stem you shorten in early summer is flowers removed from the autumn display.
Late summer to mid autumn: the payoff
The first flowers open in late summer and the plant then produces a continuous succession from buds set along the branched stems. In a mild autumn it will still be opening fresh flowers weeks after the rest of the border has finished, which is the entire reason for growing it.
Keep watering if the weather stays dry, especially in the first half of this period while the last buds are still forming. Deadhead lightly if you want, taking the individual spent flower back to its own fork and never shortening a main stem, since the buds further along it are the rest of your display.
Check the supports after the first autumn gale. A clump that has splayed outward will not stand up again, and if you catch it in the first day or two you can often lift it back and add a second ring. Note which way it went, because it will go the same way next year and you can set the support to prevent it.
Stop deadheading in mid autumn and let the last flowers turn into seed heads. The cottony white heads hold their shape well into winter and are worth having.
Late autumn and winter, and the notes that make next year easier
After frost blackens the stems, cut them to about two inches (5 cm) above the ground, but leave the basal leaves alone while they are still green, because they are feeding the crown for spring. In a cold garden with wet winters you can leave the whole top growth standing until late winter instead, which shelters the crown, and clear it all in one go before the shoots break.
Whichever you choose, do not leave cut stems lying on the crown, and keep heavy wet mulch off it. Cold does not kill this plant. A crown sitting in cold standing water through winter does.
Before the stems go, write three things down: the date the first flower opened and the date the last one faded, the height the stems reached, and the position of the outermost shoots measured from a fixed point such as a post or path edge. The first tells you which weeks of autumn this plant actually covers in your garden. The second tells you how tall to set next year's supports. The third is the only reliable way to know whether the colony is expanding, because six inches (15 cm) a year is invisible from one season to the next and unmistakable across three.
Add a note of anything unusual: the year the leaves scorched in a dry late summer, the year the clump splayed, the year the lower leaves went brown between the veins. Those entries are what turn a vague sense that something went wrong into a decision you can act on next spring.
Winter is the right time to take root cuttings if you want more plants. The clump is dormant, so scraping soil away from one side and removing a few pieces of running root does it no harm, and cuttings taken now will be shooting by spring.