The only "downside" one could argue is by having it with your clover you cannot control weeds as what won't kill chicory will kill clover and vice versa.....but honestly I don't mind weeds (well except bad grasses). I have a clover/chicory spot I plan on spot spraying the grass clumps that have fought and won out this next spring...may even kill off and restart a portion of it but go heavier on the chicory (right now probably 80% clover and 20% chicory). I might even experiment with committing a new section (just a access trail we drive only in planting and mowing time frames) with nearly 100% chicory, probably go 80% or so chicory and just fill in with clover otherwise. The deer this year as I sat on stand told me from what I was looking at they love the chicory as every blade of chicory was cut down to probably an inch (2 at most).
With proper establishment and appropriate weed tolerance you should need to spray a field for at least 5 years. At that point, you can suppress the clover with 1 qt/ac to get a couple more years out of the clover.
One downside I found was cost. A clover chicory mix worked pretty well when I was using ladino clover. The chicory with that long tap root would flourish in the summer especially during drought years when the ladino would go dormant.
When I moved to Durana clover, the chicory lost much of its added value but the cost of planting it stayed the same. Durana is slow to establish but once established it is more drought tolerant, aggressive, and persistent than ladino. So, I would only get a couple years out of the chicory before the Durana would over take it. Second, in most years, my Durana doesn't go dormant during the summer and in drought years it only goes dormant for a few weeks. So, there is less need for the drought tolerance of the chicory in my area. Also, I get an easy 7-10 years from a durana field rather than 5-7so with the chicory only lasting a couple years the value of it was not worth the cost any longer.
One more thing about chicory. Unlike clover, it requires mowing maintenance unless you have enough deer use to mow it for you. If chicory is allowed to bolt, it can produce too much seed per square foot. Timely mowing solves this, but with straight durana, I can mow once per year right before the fall rains and cool evenings favor the clover and get good results.
Keep in mind that I'm in zone 7a and the value of chicory to a clover mix will vary with location and the type of clover selected.
I am considering the potential of some pure chicory stands as a way to reduce summer soybean forage requirements and long-term cost.
Thanks,
Jack