Understory for walnut

Has any one experience with Ulex europaeus, known as gorse, in a understory with walnut.

Speaking as one who visits lots of semi-natural habitats where gorse is native in the course of work, I don't think I've ever seen Gorse growing successfully as an understorey to anything. I just can't conjure up an image of it. It forms thickets of itself. Maybe under birch, but birch is a pioneer, the gorse was probably there first.

And I have read that walnut is very unfriendly to other plants.

I only once found gorse as a understory and that was in a designed environment. It was under a trimmed sycamore. The advantage of gorse is that it dies down in the middle and tends too grow outwards. Its a nitrogen fixer and has flowers of witch you could make a wine. Goats eat the young shoots. That's where my knowledge stops. This question is more fore the European forum members I think.

Elderberry and Currants can tolerate Jugalone (the allelopathic compound in walnuts) and tend to like the same conditions. They each due fine in a sub canopy setting.

Gorse tends to prefer dry sandy soils on the low pH side. It also loves sunshine, if you go by it on a really hot day you can hear the seed pods crackling, and it smells like coconut oil. It responds well to trimming but is very painful to tread on afterwards. We have a saying here "when gorse is in flower, kissing's in season". In other words it can flower at any time of year.

I remembered, that mulberry is considered to be juglone tolerant. I thus googled for mulberry and juglone and stumbled upon this qdma forum thread
According to a post there

White Mulberry, but not Red Mulberry

Oak

Hickory

Buckeye

Peach

Pear

Wild

Plum

Black Raspberry, but not Blackberry

Willow

Hybrid Poplar

Red Cedar

Buck Brush

Osage Orange

Locust

are probably juglone tolerant.

As already mentioned above: I also have never seen gorse below anything, it usually builds thickets in sunny situations.

Here's a list of items that *should* be juglone tolerant, from my travels on the interweb:

Black Cherry, American Beech, American Hazelnut, Staghorn Sumac, Serviceberry, White Mulberry, Eastern Hemlock, Pear, Black Locust, Greenbriar, Seeded (wild) Grapes, Morning Glory, Elderberry, Hibiscus/Mallow, Bladdernut, Currants, Goumi Berry, Pole Beans, Winter Squash, Melons, Perennial Sunflower, St John's Wort, Echinacea,, Peppermint, Lambs Ear, Sweet Woodruff, Lobelia, Viola, Comfrey, Beets, Carrots and Parsnips, Onions/Garlic, Wild Ginger, Giant Solomon's Seal, Gentian, Daylilies, Jerusalem Artichoke, Hosta, Ginseng

This is stuff I decided on combining in my own guild along with hickory (also a juglone producer) in the overstory. Do note, though, I haven't even planted a single tree or seed, so mileage may vary