Planting Udo: Choosing a Permanent Bed for a Head-High Perennial

Understand the size before you choose the spot

Almost every mistake with udo starts with underestimating it. Left to grow, a single established crown throws up hollow stems that reach six to eight feet (180-240 cm) by midsummer and spread four feet (120 cm) across, with large divided leaves that shade out anything beneath them. It is closer in scale to a shrub than to a vegetable, and it dies back to nothing every winter, so the space it occupies looks empty for half the year and impassable for the other half.

That combination means udo belongs at the back of a bed, along a boundary, or in a bay of its own. Do not slot it between annual vegetable rows, and do not put it where you need to walk once it is at full summer height. A common working arrangement is a strip against a fence or hedge where the summer bulk is an asset rather than an obstruction, with a path in front that stays clear.

Sun is not critical. Udo grows well in full sun and equally well in half a day of shade, which is one of the few things that makes siting easy. What it will not tolerate is a windy, exposed position: the stems are hollow and soft, and a gale flattens a six-foot clump in an afternoon.

The plant is fully hardy well below 0F (-18C) once the crown is established, and it goes completely dormant, so nothing shows above ground from the first hard frost until spring. Mark the position with a stake before the top growth disappears or you will lose track of where the crowns are.

Soil: deep, rich and loose enough to mound

The crop is a fast, soft shoot produced in a few weeks from stored reserves, so the plant needs a soil that lets it build a large root system and hold water through a long summer. Dig the bed to a full spade's depth, or deeper if you can manage it, and work in three to four inches (8-10 cm) of well-rotted compost or manure across the whole area.

There is a second reason for good preparation that is specific to udo. In spring you will pile eight to eighteen inches (20-45 cm) of loose material over the crowns to blanch the shoots, and that mound has to sit on ground that drains. A heavy clay bed under a wet mound turns the crown into a rot risk exactly when the shoots are pushing through it.

On clay, raise the bed six inches (15 cm) above the surrounding ground and mix grit in with the compost. On sand, the priority is the opposite: fold in as much organic matter as you can spare, because a plant putting up eight feet of growth in three months runs out of water quickly in a light soil.

Setting crowns and root divisions

Plant dormant crowns or root divisions in late winter or early spring, before the buds break, while the soil is workable and not frozen. Each piece should carry at least one fat visible bud on a section of thick root four to six inches (10-15 cm) long. Handle them like asparagus crowns: they are tough, but the buds snap off easily.

1. Dig a wide hole, not a deep one Open a hole twelve to fifteen inches (30-38 cm) across and about eight inches (20 cm) deep. Udo roots run outward and downward from a compact crown, so width matters more than depth at planting time.
2. Set the bud two to three inches below the surface Position the crown so the growth bud sits under two to three inches (5-8 cm) of soil. Too shallow and the crown heaves in frost; too deep and the first spring's shoots waste stored energy before they reach the light.
3. Spread the roots outward Fan the thick roots out across the bottom of the hole rather than coiling them. A crown planted with kinked roots takes an extra season to establish and produces spindly first-year shoots.
4. Space at three feet minimum Set crowns three to four feet (90-120 cm) apart. It looks ridiculous in the first spring and correct by the second summer, when each plant has filled its allotted circle completely.
5. Firm, water and leave the surface loose Backfill, firm gently with your hands rather than your heel, and soak the area. Then break up the top inch (2.5 cm) with a fork so emerging shoots meet loose soil, not a crust.
6. Stake the position Push a tall cane in beside each crown. Udo breaks dormancy late, and an unmarked crown is easily forked through by someone tidying the bed in early spring.

Spacing and layout at a glance

These figures assume you intend to blanch, which is the only way the crop is worth eating. Blanching needs working room on all sides of each crown, so the spacing below is wider than you would use for an ornamental planting of the same species.

Plan for the third year, and write down year one

Udo is a long game. A newly planted crown should not be cut at all in its first spring and only lightly in its second; the shoots it produces in those years are what build the root reserves that pay for every harvest afterward. A crown cut hard in year one will limp along for a decade.

That patience is easier if the plan is written down rather than remembered. Record the planting date, how many crowns went in, exactly where each one sits relative to a fixed marker such as a fence post, and the size of the piece you planted. Note which crowns came from the same parent, because when one outperforms the others you will want to know whether it was the piece or the position.

Also record what the first summer's growth looked like: the height reached and the number of stems per crown. Those two numbers, compared year on year, tell you when a crown is finally ready to cut and, much later, when it has aged out and needs replacing.