Crown rot: identify, prevent, control

Updated October 2026

Worst in cold, waterlogged soil from late autumn to spring, and in warm wet spells in heavy or poorly drained ground anywhere in New Zealand.

Crown rot is the name for several soil-borne rots that attack the crown of a plant, the woody or fleshy point where the roots meet the shoots. In New Zealand gardens the main cause is Phytophthora, a water mould that thrives in wet soil, with Fusarium fungi adding to the problem in old asparagus beds. Once the crown has rotted the plant cannot be saved, so good drainage and clean planting material matter more than any spray.

Phytophthora cactorum and other Phytophthora species; Fusarium species on asparagus

How to identify it

The first thing you notice is that the youngest leaves wilt or droop on warm afternoons, even though the soil is wet.
Leaves then turn dull, bluish or yellow, growth stops, and the whole plant collapses over days or a few weeks.
When you dig up a strawberry and cut the crown lengthways, healthy tissue is white, while rotted crowns show reddish-brown or dark brown rot spreading from the base.
On rhubarb, the crown goes soft and brown, buds rot at soil level and the leaf stalks fall over; a foul smell suggests bacterial soft rot has followed.
Asparagus beds thin out as crowns die, and spears may have water-soaked brown patches at soil level that make them bend and shrivel.
Globe artichokes affected by crown rot fail to reshoot after winter, and the old crown is brown and mushy when you dig it.

What it is often confused with

Root rot

Root rot starts in the fine roots, which turn brown and slough off. With crown rot the damage is concentrated where roots and shoots join, and the roots below may still look fairly healthy.

Verticillium wilt

Verticillium wilt often shows on one side of a plant first and leaves brown streaks inside the stems or crown, while the crown stays firm. Crown rot makes the crown soft and discoloured all through.

Grass grub

Grass grub and other root-feeding larvae can also make strawberries wilt, but you will find chewed roots and C-shaped white grubs in the soil rather than a rotted crown.

When and where it is worst

Crown rot turns up wherever soil stays wet, so it is most common on heavy clay soils in Waikato, Auckland, Northland and Southland, in low-lying beds, and in any garden after a long wet winter. Strawberries in Auckland and the Bay of Plenty are often hit after warm, wet autumns, while rhubarb and asparagus losses tend to show in spring after waterlogged winters.

Phytophthora spores swim in water-filled soil and spread with rain splash, run-off and infected plants. The resting spores survive in soil for many years, so a bed that has had crown rot is a risk for the same crops again. A related strawberry disease, red core (Phytophthora fragariae), rots the roots from the inside and has been recorded in Auckland, Wellington and Canterbury since 1951.

Plants it affects

These plants in our library list it as a problem to watch for.

Asparagus Globe Artichoke Rhubarb Strawberry

How to prevent it

Buy certified, disease-free strawberry runners and asparagus crowns, and never replant strawberry runners taken from a bed where plants have collapsed.
Grow strawberries, rhubarb, asparagus and artichokes in raised beds or mounds so the crown sits above any standing water.
Improve heavy soils with compost and avoid compacting wet ground by walking on beds.
Plant crowns at the right depth: strawberry crowns should sit level with the soil surface, and rhubarb buds just at the surface, never buried deeply.
Water at the base in the morning and avoid keeping beds soggy, especially in cool weather.
Rotate strawberries to a fresh bed every three years, and do not plant them where tomatoes, potatoes or strawberries have recently grown.

Organic control, step by step

Dig out and bin collapsed plants with the soil around their roots, and do not put them in the compost.
Open up drainage around remaining plants by clearing mulch away from the crown and lifting the bed or adding a drainage channel.
Replant into a different, well-drained bed with fresh compost rather than into the same spot.
Clean spades, secateurs and boots after working in an affected bed so you do not carry infested soil to clean areas.

Conventional control

We could not find a New Zealand home garden product registered for Phytophthora crown rot on strawberries, asparagus or globe artichokes, so prevention is your control for those crops.
Some liquid copper fungicide labels list crown rot of rhubarb; if the product you buy includes it, drench the crown area at the label rate in autumn and spring.
Phosphorous acid products are used by commercial growers and nurseries in New Zealand against Phytophthora, but check that a product is approved for home use and that your crop is on the label before using one.
Always read the label, check that your crop and crown rot are listed, and keep to the withholding period before you harvest.

Frequently asked questions

Can a plant recover from crown rot?

No. Once the crown is rotted the plant cannot move water to its leaves, so it will keep declining. Remove it and put your effort into protecting the healthy plants around it.

Can I replant strawberries in the same bed?

Not for several years. Phytophthora survives in the soil for a long time, so plant your new runners in a different, well-drained bed and grow something unrelated, such as sweetcorn or brassicas, in the old one.

Why is my rhubarb rotting at the base?

Rhubarb crowns rot when they sit in cold, wet soil over winter or are planted too deep. Lift the plant, cut away any soft brown parts, and replant healthy pieces in a raised, free-draining spot.

Is crown rot the same as root rot?

They are closely related and often caused by the same water moulds. Crown rot is the name used when the damage is at the base of the shoots, and root rot when the fine roots go first.