Mulching invasive European Buckthorn (Rhamnus catharticus) with berries

I have recently acquired a little 3 acre farmlet in central Wisconsin. Currently we are farming nothing but a small flock of chickens, but we’d like to replace the massive grassy lawn with native flowers and a small orchard.

The property is ringed by a narrow strip of trees and shrubs, and I have been able to identify a thick infestation of European buckthorn choking out the understory. I am beginning the process of eliminating the buckthorn with hopes of replacing it with some native or at least more useful plants by cutting down all of the seed-bearing individuals.

My conundrum is this: I would like to take advantage of the large amount of wood I am getting from limbing up the berried buckthorn (and some seeded boxelder) by running it through an electric chipper. I figure I can use the chips to make mulch for native flower beds I want to put in next year. However, I am wary of chipping up branches with bunches of ripe berries on them for fear that I will simply be spreading those seeds to my potential mulched up beds.

Any suggestions on what to do? Are my concerns unfounded? I am open to other ideas or methods, though my resources are limited (e.g. I would like to eventually like trying making biochar from the stuff, but lack the time and the inclination to set up a proper burning apparatus for it right now).

Could you hold off on chipping until after the berries are gone? I don't know anything about European buckthorn, so not sure if they are deciduous or flower/fruit all year, etc.
Some of the best chips I've gotten were from early spring, after the trees have come out of dormancy and are full of lush, green growth; but before they start blooming or fruiting heavily.
Last fall I got a bunch of elm chips that were full of berries and a ton of them came up in the gardens & flower beds in spring, so it's definitely something to be wary of. I've also had elm & oak chips that have sat and composted for 2-3 years before using them, and they still had viable berries and acorns that came up after I finally put them in the beds.
But- you're definitely on the right track with a good permie solution! I think it's just going to be one of those things where you have to get the timing right. 🙂

I have the same issue with Himalayan blackberry, which I am trying to eradicate from my property.  I do chip the dried canes and they make great mulch because they take so long to decompose.  I police my property every few months to cut down or weed any new shoots of it.  I think as long as you are willing to do that, you'll be okay.  Besides you'll know exactly where you put that mulch, so you'll know where to keep a watchful eye on buckthorn seedlings.

Of course you can go ahead and mulch it all up. It is regarded an invasive weed in US. But what of it's function as a wind break?
You would lose out on a lot of the moisture retaining qualities an infestation offers. Birds arrive to feast on the berries and leave their droppings, fertilizing the lands. Maybe in the shrubs larger trees will find a place to grow. And if they don't yet you can make it that way.
I might sound like a grand-pa whining about saving a nuisance, but i would love to have an established wind breaking hedge on my production plot, i am struggling to establish one for three years now because of record droughts. I can grow no salads in summer, they all wither, so i am contemplating growing some on a slope under some old oaks, they'll shade the salads.
You could also consider managing the shrubs, taking them out here and there.
If it's woodchip mulch you want, there are other ways, companies dump truckloads for free. Chipping with an electric chipper is so time-consuming it's almost a waste of time.
Rambling, rambling, how high is it anyway?