Even if we’re talking one of those Main Line country clubs, I’ll take that bet. 
I’ve worked several afternoon weddings in my time with nary a gown in sight. So there may be a couple of gowns, but I’m predicting it will be a small number.
I think you are overthinking this. It’s your D attending and it’s a friend’s wedding, so if she’s comfortable, you should be too. I doubt she’ll embarrass anyone. It’s the bride’s day, so I doubt she, or anyone else will focus on D’s dress.
I recently attended a semi-formal wedding at Northstar resort. The ceremony started at 4:30 (per invitation but actually 5:30). Folks wore a huge variety of outfits from button down shirts to suits for the men and pretty much anything for the females—gowns and all lengths of dresses, floral and solid print. Mother Of the groom was in a black with roses gown.
This is the website where I found my pretty long floral dress. They have a lot of lovely things.
I like your dress, @VeryHappy. I was thinking of that dress when OP posted this.
The black tie optional weddings we attended ran the gamut of dress. There were always a couple of grandmas in gowns, but most people were just “regular dresses”. Florals can be dressed up with the right accessories. I agree with not worrying too much about it, especially since it’s for a friend, not a boss!
It needs to be instagram worthy.
I’ve got a non-optional black tie wedding (6:00) pm to go to in a couple of weeks and am waffling on what to wear. It’s likely to be over 100 degrees here in Texas and even if I go sleeveless, a long formal gown seems like torture. Especially in black, which seems to be most appropriate for a 64 year old.
Attended a wedding this past Saturday. Mass was in the Villanova church and the reception was at a country xlub five minutes away (so yes, the Main Line). Cocktails outside from 5:00-6:30 and it was broiling hot. It was not black tie so I saw nothing floor length (other than bridesmaids, mother of the bride and bride of course). Lots of pretty floral dresses, most sleeveless, and a few cocktail dresses on the over-60 guests. My poor Sister in law was in a cream long sleeve dress with lace overlay and just wilted. I felt lucky that I had grabbed a sleeveless floral dress that morning at TJ Maxx when I saw the weather forecast; I would have been miserable in the fancier dress I had originally planned to wear. So cool, comfortable and pretty wins out over technically correct in my book.
I think the floral dress for that time of day is appropriate. However, I’d dress it up with jewelry and shoes…even a hairstyle!
@preironic I’m old-fashioned enough to think you can’t wear black or white to a wedding, but new fashioned enough I’m okay with florals. I do agree if you wear a floral print you may need some bling or something else to look dressed up.
mathmom - I understand white but no black even to a black tie wedding? I’m looking at one dress that has black lace over a lighter color.
Absolutely beautiful dresses at www.yumikim.com! But I can’t spend anywhere near that much money for a dress I’ll wear once. Wish I could!
We recently had a black tie optional, Friday night wedding at a northern NJ country club. I was prepared to be the only one not in a gown, but almost nobody was in a gown, outside of the wedding party and parents of the bride and groom. The majority of the 20 somethings had the usual ahort, tight, black dress. I think tea length floral for outdoors in the summer is prefect, assuming a dressy floral.
Black tie optional to me means we really want the guys to wear a tux, but come in a dark suit if you don’t own a tux and can’t afford to rent one.
Many floral dresses marketed to the millennials can look like sundresses. Not saying the OP’s D’s does as we have not seen it. I think “black tie optional” signals just that - a notch of formally, even for a daytime wedding. Besides, one would not want to be that one person wearing a flowy floral amongst a sea of more formal cocktail attire. That said, there are lovely florals that can work well for a formal daytime event. Usually it means more expensive fabrics, a notch more structure, some beading, embellishments, etc.
Like this one (I just happened to browse the site, so here is a gently loved one):
https://www.therealreal.com/products/women/clothing/dresses/lela-rose-776
^^^^yes, it’s a large floral print. Beautiful for the right occasion, but not for black tie optional.
I would wear BB’s real real dress to a back-tie optional wedding!
And I can see a 20-something wearing this to such a wedding: http://www.lordandtaylor.com/main/ProductDetail.jsp?FOLDER%3C%3Efolder_id=2534374302023792&PRODUCT%3C%3Eprd_id=845524442506862&R=191151502090&P_name=Tahari+Arthur+S.+Levine&N=302023792+4294929611+4294929441&bmUID=mjZ684e
Just saw pics from a black tie optional very small wedding of friends. The venue required jackets and ties and about half the young men wore a tux. The women young and old had hi-low to floor length and really pretty floaty florals. It was outside and gorgeous! MOB had a solid top, floral bottom full length gown. But I have never heard of black tie in the middle of the afternoon. I agree that it is probably the bride and groom signalling guests to notch it up from a collared shirt, khaki pants for guys and bandage dress or short sundress for the ladies.
So…what does “semi formal” mean on a wedding invite? We are going to an evening wedding on the beach with reception at a country club. I’m actually wearing a silk sundress with wrap to the beach wedding, and then changing to a silk dress for the reception.
But TBH, my very pretty silk sundress and wrap, I think would be quite nice even at the reception…so…I might not change. And really, it would be fine IMO to a black tie optional event with the right jewelry.
To my niece who had a semi-formal wedding at Northstar, semi-formal meant for males to wear a suit if they had one (button down, collared shirt if they didn’t) and females to be dressier than sundress. There was a wide range of attire for everyone — floral dresses, solid-colored, short, tea length, and maxi-dresses. Men wore suits and some just button down shirts and dress slacks.
The wedding I just attended had no dress code I was informed of. Everyone just dressed as they pleased. There was the entire gamut again. I guess most of the weddings I attend don’t have a dress code and expect guests to use their good taste.