Crown Gall: Rough, Warty Growths on Stems and Roots That Aren't Normal

Crown gall is one of the most fascinating — and troubling — diseases a houseplant can develop. It's caused by a soil-borne bacterium called Agrobacterium tumefaciens, which essentially hijacks your plant's own genetics: the bacterium injects a fragment of its DNA (called T-DNA) directly into the plant's chromosomes, reprogramming cells to produce hormones that trigger runaway tumor growth. The result is rough, corky, wart-like lumps that appear at the soil line, on roots, or at stem wounds — and because the cause is baked into the plant's own DNA, there is no cure once infection takes hold.

Crown gall is far more common on outdoor woody plants — roses, fruit trees, and shrubs — than on typical houseplants, but it can arrive in your home on a newly purchased cutting or bareroot plant. Because the early growths can look a lot like normal wound callus, edema bumps, or even the corky scabs that sometimes form on succulents, accurate identification matters before you take any action. This page walks you through exactly what crown gall looks like, what it isn't, and how to respond if you genuinely suspect your plant has it.

Signs to look for

• Rounded, wart-like or cauliflower-textured swellings appearing at or just below the soil line, at the root crown, or at stem wound sites.
• Young galls are smooth, white or cream-colored, and slightly spongy; older galls harden and turn brown or tan, developing a rough, cracked, woody surface.
• Galls are solid all the way through — not hollow — and when cut open, the interior lacks normal annual growth rings and is softer than healthy surrounding wood.
• Growths do not produce leaves, buds, or stems (distinguishing crown gall from fasciation or leafy gall caused by Rhodococcus fascians).
• Multiple galls may appear over time, including secondary growths away from the original infection site — especially after the plant is repotted or pruned and new wounds are created.
• Mildly stunted growth, increased vulnerability to drought stress, or wilting in warm weather — especially if a large gall partially girdles the root crown and restricts water uptake.

What causes it

How to fix it

1. 1
   Confirm the diagnosis before acting

   Look carefully at the growth in question. A true crown gall is solid, has no internal growth rings when cut, and does not produce any leaf or bud tissue. It appears at wound sites or the root crown — not randomly on flat stem surfaces. Confused by what you're seeing? Compare against edema (small, corky blisters on leaf undersides or stems caused by overwatering), oedema bumps, corky scab on succulents, aerial root nubs on climbing plants like pothos and monstera, and normal wound callus before concluding it's crown gall. If in doubt, consult a cooperative extension plant diagnostic clinic — molecular methods can confirm Agrobacterium identity definitively.

2. 2
   Isolate the plant immediately

   Move the suspected plant away from the rest of your collection. Although Agrobacterium spreads mainly through soil contact and shared tools rather than through the air, isolating the plant prevents you from accidentally moving contaminated soil to healthy pots during watering or maintenance.

3. 3
   Assess whether the plant is worth keeping

   There is no chemical treatment and no cure for crown gall once a plant is infected. For lightly affected plants with a single small gall and otherwise healthy growth, some gardeners choose to keep the plant and manage it carefully. For plants with large galls that encircle the root crown or multiple spreading tumors, removal and disposal (in the trash, not compost) is the most responsible decision to protect the rest of your collection.

4. 4
   Do not attempt to cut away the gall

   Cutting into a gall releases Agrobacterium cells into the wound and surrounding soil, and the cutting tool becomes a vector. If you handle the affected plant, wash your hands thoroughly afterward and disinfect any tools that came into contact with the galls or surrounding soil with 70% isopropyl alcohol or a 10% bleach solution before using them on other plants.

5. 5
   Dispose of the soil safely

   Discard all soil from the infected plant's pot. Do not reuse it or add it to outdoor beds. Agrobacterium can persist in soil without a host, so the safest route is to bag the soil and put it in household trash. Wash the pot thoroughly with soap and water, then disinfect it with a dilute bleach solution before reusing it.

6. 6
   Monitor neighboring plants

   If the infected plant shared a drip tray, was watered with the same can without rinsing, or had roots that touched neighboring pots, inspect those plants at the soil line and root crown over the coming weeks. Early galls — smooth, cream-colored swellings — are easy to miss at first glance.

How to prevent it

• Buy plants from reputable nurseries and inspect the root crown and stem base carefully before purchasing — look for any swellings or rough, corky growths at or below the soil line.
• Sterilize pruning tools and repotting equipment between plants using 70% isopropyl alcohol; wounds are the sole entry point for Agrobacterium, and clean tools mean clean cuts.
• Avoid unnecessary wounding during repotting — handle roots gently, and if roots are broken or cut, give the plant a few days to dry the wound before placing it in fresh soil.
• Never reuse potting soil from an unknown or suspect source; fresh, sterile potting mix for each repot is your single best line of defense against soil-borne pathogens.
• For woody cuttings or new bareroot plants where crown gall is a concern (especially roses or figs), a biological control product containing beneficial bacteria — such as those in the NoGall formulation — can be used as a preventive dip before planting; these beneficial bacteria preemptively colonize wound sites and produce an antibiotic that inhibits Agrobacterium tumefaciens.