Broccoli and Mustard Greens
Antagonist Pair — Keep Apart
This is the same well-characterized plant pathology covered for cabbage and mustard greens - clubroot doesn't distinguish between brassica species, so the evidence applies here without needing separate confirmation.
Mechanism: Shared Disease Risk
Broccoli and mustard greens are both brassicas susceptible to clubroot, the soilborne pathogen documented at length on this site's cabbage-and-mustard-greens page, along with shared flea beetle pressure common across the brassica family.
Broccoli and mustard greens run into the identical clubroot risk documented in more depth on this site's cabbage-and-mustard-greens page, since the pathogen doesn't care which brassica it's infecting.
The Same Disease, a Different Brassica Pair
Clubroot's resting spores persist in soil for years once established and infect the full range of brassica crops, broccoli and mustard greens included - this pairing doesn't need its own separate proof, since the underlying pathogen's host range is already well documented across the brassica family.
Mustard greens grow considerably faster than broccoli, often ready to harvest in under 40 days versus broccoli's two to three months, which means a mustard greens planting can come and go multiple times within a single broccoli season - each cycle still counts as brassica exposure for rotation purposes, even though it doesn't look like a long-term planting.
Spacing
Treat this the same as any two brassicas in rotation planning - spacing within a single season matters less than not repeating brassica crops in the same soil year after year.
Watch For
See this site's cabbage-and-mustard-greens page for the full clubroot picture - the short version is: rotate brassicas as a group, and don't follow one with another in the same bed without a multi-year break if clubroot has ever been confirmed there.
Frequently Asked Questions
Is this a different disease risk than cabbage and mustard greens?
No - it's the same clubroot pathogen, which infects brassica crops broadly rather than being specific to any one species. Treat broccoli, cabbage, and mustard greens as a single rotation group for this reason.
Does a quick mustard greens crop count against my brassica rotation the same as a full-season broccoli planting?
Yes - even a fast, under-40-day mustard greens crop is still a brassica occupying that soil, so it counts toward rotation planning the same as a longer-season crop like broccoli, regardless of how briefly it's actually in the ground.