The bottom floor does seem to be about 10F. Below that there is die-back. This makes it a USDA 8 item at best (0-10F, 10-20F etc. are ranges of average minimum temperatures, not the coldest it gets in these zones).

Away from outer coastal/cloud forest type of environments light shade is ideal. Hot sun is tolerated but foliage appearance not as good. Much shade makes it lean toward the light and so on.

Yes, I've had them outside the front door in the full east wind for over ten years. Full sun until 3PM. It has had no weather damage or insect pests. It attracts early-season bumblebees.

This gets to be a very large bush unless you trim it twice yearly and do a major pruning every few years. It wants to block our dining room window in no time.

The fruit, if allowed to fully ripen (will start to shrivel and drop) yields an excellent sweet juice. Pick them before they shrivel to the point of drying out--then you have barberry raisins.

Pictures from 2006:

>Full sun until 3PMSo during the hottest time of the day a shadow is over the planting site.

Yes, the house shadow.

The Darwins have been successful for me, but I don't recall seeing any others in my SE Portland travels, even though you can see various barberries on every block.

There is a Darwin still in the plant list for the Elk Rock Garden, it would be older than my plants. Not as much east wind there.

I don't remember it there, but I have not been for some time. There are numbers of them here and there in the Seattle area. Local garden centers continue to stock it. Up here it is the colder winters only that get down to 10F, except in outlying communities. But even near the Sound there is significant variation, with the record lows at the international airport (Tukwila) 0F and at the University (Montlake) 10F.

In Portland the airport has had something like -3F.

It was in the late 1990's we visited the Elk Rock garden. The Darwin then was already rangy.

Here in Portland, single-digit temperatures right in town are so rare that the home gardener can treat the possibility with impunity.

The -3F in January 1950 was part of an anomalous week of low temperatures. The last time the temps went single was in 1989 (two 9's) and then back to 1972 (8).

But the next single digit temp will probably happen before the next big quake.

I wanted to grow one because of the edible fruit, and the Bishop's Close garden was supposed to have them in Portland, but I went there last fall and couldn't find them. Well, I guess I am chicken to grow it in the open, so I will put it on the south side of the house where a Loquat grows (but doesn't flower or fruit). I lost a small olive tree there last winter.

I am at a higher elevation and it has gotten down to 6* F here that I know of, happening at the first very late frost, and it killed a big eucalyptus tree supposedly hardy to 0* F.

But my little Azara microphylla is still alive, though it has not grown much and is on the NE side of the house but 20' away. I was actually thinking of moving it to the south side of the house. It is supposed to be hardy to 5-10* F and Berberis darwinii to 0* F (7a) according to one site. I did put a clear plastic cloche umbrella over the Azara last winter which did seem to help.

Due to sun hitting the frozen leaves during sharp cold and exploding them a broad-leaved evergreen of this type would probably be better off even in the full shade of the north side of the house than an unshaded south exposure. It seem this particular shrub might also burn during summer temps in the 90s or above on a south wall. Like the Azara it is from a cool southern South American region, which is why it is grown in this comparatively similar climate region.

The last real killer winter here was in 1990. Lots of stuff was adversely affected, as I recall long-established Darwin barberries were burnt but didn't necessarily die. 0F could be someone's idea of what it takes to kill the shrub, rather than the point where it starts to be noticeably damaged. Or it's based on the idea that the plant is hardy to USDA 7 and the temperature range given for that zone is 0-10F. But 0-10F is the AVERAGE annual minimum temperature, not the coldest it gets there - Darwin barberry persisting in USDA 7 I find highly questionable, as it would have to be subzero hardy to take all winters there.

It being a wild species there could be some variation between forms. I believe D. Hinkley introduced one or more additional forms from the wild when he and his partner were operating the Heronswood nursery.

I have one that gets afternoon sun in the winter and is somewhat sheltered from the east wind. I interplanted it with ceanothus which has died, along with the replaced one, but the Berberis doesn't seem to show any damage.

The one at Bishop's Close is up on the terrace in front of the Hamamelis. It's huge.

I thought of that area when trying to remember where it might be.

In case it may pertain to any examples mentioned here sometimes its hybrid Berberis x stenophylla is mistaken for it.

I just looked at Bishop's Close for a map, I forgot the garden was called Elk Rock Garden mentioned above. What is the exposure of the terrace? Is that next to the house? I can't see it labeled on the Elk Rock garden map.

There are a couple of large red cedars on the south side of my house so there is not a lot of direct sun there, just a nice concrete wall that has sloped banks on the south and north ends of the house then earth-bermed walls on the east and west. I can't think of any open locations to plant it where it would be near concrete to keep the ground warmer.

The terrace was out in the open, but near enough to larger trees to be shaded some of the day.

Putting this plant near a wall will alter its growth habit a lot.

I have two plants; one fruits sparsely but reliably; the other, 4 feet away, seldom fruits , even though the bloom is not sparse and sun exposure is equal. Of course I am pruning to the detriment of fruit production.

The Bishop's Close plant is probably ripening fruit right now and may be worth a visit.

I'd say the terrace with the witch hazels faced an easterly direction, as it looks towards the river and most of the garden is south of it. There has been a shadow over it most times I have been there.

I see it's called "The Parterres" and it faces northeast, as I thought it might.

(Link is to an enlarged view of a map presented in pdf format, you need to have scripts allowed and wait a little bit for it to open)

Here is a link that might be useful: ELK ROCK, THE GARDEN OF THE BISHOPâS CLOSE

I saw the map but it is upside-down, north is down, so right is northwest, the river is to the east. I'm still confused but I may try to just plant the B. darwinii where it will perform best as a deer barrier and surround it with some large rocks to add heat, and take some cuttings to propagate it if possible. Thanks!

I wouldn't do anything to try to make the spot hot in any way.

Yes, south is at the top, with the river on the left and the parterres on the right. These slope toward the river.

We've really pinned this plant down. Unless you would like me to take some GPS readings.

Thanks for your help, I'll have to try to go see it but it is around 30 miles away and I'm mostly in Portland in the evening when the garden is closed.

Well worth visiting regardless of the barberry being there. Most general types of ornamental plants are represented, including bulbs.