this is funny.When i just did a search on GW, i found that i asked a similar question last year in feb! but not specifically about ascot rainbow. Anyone have additional/updated info here?! thanks much,
mindy
last yr's thread:
http://forums2.gardenweb.com/forums/load/peren/msg021507052043.html

I've had confirmation from two sources that it has survived consequtive winters in western Michigan z5.

oooh yay! thanks much!

It's on my "must-plant" list for this year. I've been meaning to do it for a couple of years now. ;)

I have no knowledge of 'Ascot Rainbow' but can attest to Euphorbia 'First Blush' hardiness here. A real winner!
{{gwi:202606}}
Gets about 1.5 feet tall and stays nice and bushy all season, with fabulous foliage that turns red with spring or fall coolness.
Here it is in the landscape.
{{gwi:202607}}
Might be a substitute if need be.
Flora

sans the flowers.. they look a lot like my collection of variegated daphne ...

ken

Garden Crossings has Ascot Rainbow and has it listed as zone 5. I'm surprised as I've wanted it and now it will be mine!

jimmy

No help at all for your zone, Mindy, but my Ascot Rainbow survived our unusually nasty winter just fine in a 2G container. In fact, it is now setting flower buds and pushing new basal growth. Foliage color is very interesting and is still showing a lot of its winter red tones.

A 'Ruby Glow' euphorb in a much larger container is not looking nearly as robust. I just don't have very good luck with the purple leafed euhorbs :-)

flora, i really like the combo w/ it and the low ppl sedum. I'd love to see a berberis helmond's pillar to the left of the lilies to provide a constant dark ppl for the euphorbia foliage to play off.
best,
mindy
www.cottonarboretum.com/

I was googling online about this very subject and was pleased to find this topic. Though I'm still unsure of answer. I purchased 3 of these from Santa Rosa Gardens when they were on sale. Then, upon recieving them, I started researching and getting conflicting info. Online,after a lot of browsing, sources state EVERYTHING from hardiness to zone 5, 6, 6B (whatever that is) to zone 7. The tag with the plants SEEMS to say hardy to minus 10 degrees, though it's hard to make out, as the "minus" sign in front of the 10 almost appears like a smudge. However, the site I got it from (Santa Rosa Gardens states zone 6).

I'm growing in 3 pots for now, but would love to place in the ground. Consequently, would hate to lose them in our zone 6 winters (SW PA). Some plants I don't care if they may perish, others I like more... it must be novelty.

It's SO hard for me to believe that one plant can be listed in so many diffferent sources as so many diff. hardiness zones. I always tend to plan for an unusually cold, nasty winter.. that may happen. I guess I could always dig up in late autumn and place in pots to store in protected area (basement).

I do love the looks of this plant, and hey... if they must stay in pots, so be it. I'll be interested further on in more info about hardiness as it becomes more available.

I also think of additional winter protection if they were in ground, but don't want to rot or otherwise harm a plant that doesn't seem to appreciate excessive moisture. I know my response to this is outdated, as compared to the original posts here.

Amy, never hesitate to chirp into a past thread!it's the accumulation and timing luck that let us all spread the knowledge. Your experience with various websites/nurseries claiming various different zone hardiness is COMMON, unfortunately. Depending upon the source, the info can be actual experienced fact - or 'fact' derived from another, un-tested, source. The zone hardiness issue is one of the main plusses of GW forums- for me. ACTUAL people get to weigh in on ACTUAL experiences with plants they are growing.

Maybe you are new to GW? The member sign-up page maybe is confusing but it is best for you and us if you put your moniker followed by your zone and location, particularly
important for zone discussions!! Many of us list our zone and part of what state (So.IL) or more specifically (Chicago,IL); the more specific the better, but it's whatever you're comfortable with..... If you want to have your email address accessible, you might want to put it on your member page and not included in your moniker.

Also PA has a pretty active/very knowledgeable base of GWers, and their own forum, so you might want to copy and paste your question there as well. Also,your own PA. Chanticleer and Longwood Gardens are among U.S. gardens with the most knowledgeable and brilliant staffs.With a simple single question like this, you may be able to get an answer with an email or phone inquiry, once you figure out who to contact.

best,
mindy
www.cottonarboretum.com/

Mine survived this mild winter in zone 5b, but I am not sure how to prune it. My other euphorbias die Back to the ground, but this did not. It is showing new growth on the ends of stems with lots of dead foliage. Do I leave them or cut them off?

You get a lot of conflicting information on when/how to prune this plant. As both of its parent plants are evergreen, I treat it as a fully evergreen form of euphorbia (which it is in my climate) and hard prune old flowering stems to the ground each season after flowering. Once the stem of an evergreen euphorb has produced its terminal cyme of flowers, it will not rebloom, so evenutally you will get a lot of half-dead, partially leafed stems crowding out the plant if you do not remove.

FWIW, by the time you are ready to cut off the old flower stems, the plant should have produced a new season of basal growth, which will provide the following spring's flowers.

STEVE,just want to th you for that terrifically informative post. V Helpful!

Here's a blog entry about Euphorbia Ascot Rainbow from Avant Gardens, a nursery in Dartmouth, MA which is in zone 6. It shares their observations from growing it in pots and in the ground.

Here is a link that might be useful: Euphorbia Ascot Rainbow