Dividing rhubarb now: how to get thick stalks back from a tired old crown

Frau Schneider asked me last week why her rhubarb had suddenly started producing stalks as thin as a finger. Four years ago, those were thick red stems, thick as a thumb. She assumed poor soil at first, fertilised, watered more. No improvement.

The problem wasn't a deficiency. It was the opposite. Her crown has sat in the same spot for seven years, and underground it's tangled itself into a dense knot of old and new buds. The fuller that gets, the more shoots have to share the same limited root mass — and every single one gets weaker.

How to tell your crown needs it

A few signs that showed up the same way for me and for Frau Schneider:

• Stalks get thinner year after year, even though your care hasn't changed.
• The centre of the crown barely sprouts any more, only the outer edge is still vigorous.
• Your total harvest drops even though the plant looks bigger than it used to.

Five to eight years after planting, this is completely normal. Rhubarb is a perennial that happily lives 15, 20 years in the same spot — but not without this one reset in between.

Why October and not April

Dividing works in theory at two points: early spring, before the first leaves unfurl, or now in autumn, once the foliage dies back on its own and the plant goes dormant. I prefer the autumn slot, for a simple reason: soil temperature here in Zurich-Affoltern is still sitting around 10 to 12°C in October. Freshly divided pieces put out fine new roots in that soil over the next four or five weeks, before the ground turns properly cold. In spring, by contrast, a freshly divided plant has to compete with its own new growth for energy right away — that costs it extra in year one.

In the Erntezeit plant database, the autumn planting window for rhubarb runs from week 40 to 46 — you're right in the middle of it this week, not too late.

How to divide the crown

1. Dig out the whole crown generously with a garden fork, not just lifting one side. Roots often go down 40 to 50 cm, and a fork is gentler on them than a spade.
2. Shake or hose off the coarse soil until you can clearly see the crown with its individual buds — the "eyes". They look like small reddish knobs on the upper surface.
3. Cut the crown into pieces with a clean, sharp spade or a sturdy knife. Each piece needs at least one strong eye and a decent chunk of root attached — an eye on its own with no root mass usually just dries out.
4. Discard the old, woody centre of the crown if there is one. It barely sprouts any more, so it's not worth keeping.
5. Replant the pieces the same day if you can. Rhubarb divisions left lying around dry out fast at the cut surface.

Replanting: depth and spacing

Set each piece so the topmost eye sits right at soil level, or at most 2 cm below it — plant too deep and next spring's shoots struggle to push through. Work mature compost into the planting hole as you go; rhubarb is a moderate feeder and rewards a good start with stronger growth in year one.

Leave about 100 cm between planting spots. That feels overly generous in October, but on a mature crown with a leaf spread of over a metre, that gap turns out exactly right.

One year of patience, then harvest again

This is the part fewest people want to hear: don't harvest anything the first spring after dividing, no matter how tempting those first red stalks look. The plant needs the whole season to rebuild a root system that can actually support it from that small division. By the second spring you can harvest lightly, and from year three onward, as usual.

Frau Schneider's old crown was in exactly that state — too dense, too old in the centre. The three of us divided it last Wednesday: one piece back in its old spot, two pieces as a gift for her neighbour, who's been asking for years whether she could have "some of that famous rhubarb". Next year, Frau Schneider's single crown turns into a small rhubarb clan across the whole street — and in two years, everyone will have thumb-thick stalks again.

🦔 Stachi