The do it yourself is because I am frugal. Or, you know, cheap. And the money you save on flowers can be better spent on good food, pretty clothes, and not debt. However, if you are short on time and have elaborate plans, read this before hiring a florist. Unless you have the most excellent florist in the world, wandering in and requesting "steampunk flowers" is going to get you a very expensive bunch of peonies- defining your desires before talking to a vendor is a good plan.
Please- if you want to do something, and I say it's a bad idea, don't listen to me! If you want pin a fascinator made entirely of gears into your hair, do so! Smack everyone with a giant bouquet of pink peonies and red roses! Tuck a huge bunch of cypress into your buttonhole because you love the smell! My tips are lifted from Victorian and Edwardian fashion- and blindly following the strictures of a culture that had some pretty horrible aspects is a bad idea. People may tell you that your decisions are wrong, but what do they know? (Incidentally, 70% of wedding guest judgement can be headed off by a.) feeding them something as soon as possible- because while you may be too excited to eat, they are not, and in the process of struggling into fancy clothes and handing kids off to sitters and finding your venue, they may have neglected to eat. The ideal wedding is one with canapes at the ceremony. Also, b.) talk to each and every guest for minutes. Multiple minutes. One of the limits on the guest list should be the number of people the bridal couple can manage to exchange pleasantries with over four hours.)
It's hard to work flowers into the general mad science milieu of steampunk. There is no earthly reason they would ever have cogs on them, unless cogs were a sort of family sigil. I am also confused about the tendency to wrap everything in wire cages, as if it were a sort of science experiment that might attack the guests at any moment. I could understand if one made cogs and wire into little floral representations- tiny machines that grew and bloomed, but no one seems to be doing that. I think that the best route is to copy the floral styles of the era where steampunk is putatively set; thus we can explore the complex world of Victorian Flower Arrangements.
During Victorian times, weddings were... not more modest, because if one was rich, few things were modest... let us say only twenty percent more elaborate than a standard social event. As such, flowers would come from the usual flower sources: gardens, hothouses, young women selling flowers in the street, and the end results of obsessive craft projects. I don't have much to say about cloth, wax, and paper flowers other than they are entirely accurate, quite pretty, and if you place no value on your own time, quite affordable.
Hothouse flowers are excellent choices- consider orchids, night blooming cereus (probably as a hair ornament), waxflower, tuberoses, amaryllis, and loads of beautiful ferns . Keep in mind that they would be the end product of years of labor and diligent effort from people who did not have to spend effort on anything. Thus, two or three perfect specimens of one kind of flower surrounded by greenery is a wise choice.
If you want armfuls and armfuls of flowers, go for garden plants. Here is a list of common garden flowers- be warned that some of them have inappropriate meanings in the language of flowers- although if you are quite introverted and under significant external pressure to have a large wedding, throwing around aconite might give you some pleasure. Simple bouquets are a perfect choice- here are excellent instructions on how to make your own. Try for flowers that are in season- not only will they be more authentic, but you'll also get healthier flowers. (more on this later on.) Consider old rose varietals- like those found here. Please avoid deep red roses, since that gives us a bit too much information on what the newlyweds are planning after the wedding; it is not quite nice. Other common cutting flowers are irises, delphiniums, and lilies. (Lilies are not just for funerals.) It is entirely appropriate to deck out bridesmaids and groomsmen in flowers that are not so expensive- such as daisies, sunflowers, globe amaranth, and asters. If you want to use little bunches of wheat, thyme, or houseleeks as boutonnieres- oh my goodness, that would be delightful. For fillers and greenery, old standbys are perfect: baby's breath is very very traditional, as is gorse, assorted ferns, fennel, rosemary, and ivy. Victorians were also all about beautiful multicolored coleus- the bronze and red varieties could give a bouquet a wonderful Gothic look. The variegated green and white varieties give a cheerful and fresh impression.
I think the buy-it-from-Eliza-Doolittle version could be rather sweet too- especially for a courthouse wedding. It would be as if one were walking to church for the banns reading and picked up some flowers along the way. Good choices for a boutonniere would be violets, a bachelor's button, or a bronze chrysanthemum. A posey could have lily of the valley, primroses, coreopsis, or daisies. (and ivy. Always ivy.)
I'm going to push heavily that everyone considering a steampunk wedding include orange blossoms and ivy. Ivy is a nice bit of greenery- cheap, durable, handsome, probably strangling one of your friends' gardens- and it symbolizes everything I hope for in each marriage: love, friendship, fidelity, and affection. It's good for you. Orange blossoms were once de rigueur in hair ornaments. While the symbolism of innocence and fecundity is a bit dated, it also symbolizes eternal love and fiscal well being. (The only other plant that symbolizes money is cabbage. I don't think that will be an easy sell.) The orange tree flowers while it bears fruit- thus the fertility association- but I like to think of it as the flower of multitaskers. Moreover, they are elegant, they smell like heaven, and the wax and silk versions look as nice as the real thing. You could either hot glue them to a delicate wreath or string them on a pretty ribbon, following each blossom with a knot. (These two methods and the braiding stems method result in the best wreaths for hair. If you want a fascinator, modify the hot glue technique with a comb or clip.) Either way, do it no earlier than the night before the wedding, and keep them in a refrigerator or cooler until the last minute.
There was some sort of sea change about six years ago, and everyone decided that peonies were perfect flowers for bouquets. Unfortunately, they have a season that is about six minutes long. I'm going to add my voice to the growing chorus advocating cabbage roses- just as pretty, and much more durable. If you must plan on peonies- and for goodness sake, make your reasons sentimental, not aesthetic- have a backup plan. A day of the wedding, paid $90 for a dozen sealed buds backup plan.
It's tempting to throw giant flower arrangements on each table- and if you can manage to do so, please indulge yourself. It would be historically accurate to have piles of apples, lemons, oranges, pomegranates, strawberries, candies, and chestnuts. This does assume you are from a place where those who linger in the street will end up with a grocery bag stuffed with citrus. (Signs you live in California) Still, using food as a decoration does provide food for your guests- and loaves of bread and wheels of cheese are quite pretty. I'd also like to push vivariums- little living gardens full of inexpensive plants. Dollar stores sell charming wide cylindrical vases and yard sales are full of old fish bowls. Either plant things a couple of weeks before hand so that the weak have time to die and be replaced, or wait until a few days before the wedding so nothing has time to get sick. (Or neglect adding soil at all, and frantically stuff them all the morning before the ceremony. That's what we did. It looked very nice.) During the Edwardian era, people were mad for ferns, so consider several species. Other good choices are cyclamens, irish moss, or violets. Cacti and succulents are another beautiful vivarium. If one wanted a tropical version, orchids or African violets would be striking- with philodendron and spider plants. Add rocks, bark, and whatever tiny landscaping you think is necessary. (One could skip the entire viviarium aspect, and just stick an orchid on each table. This would combine well with a hothouse bouquet.)
Other bits of general do-it-yourself floral advice: don't avoid modern methods of crafting. Hot glue is your friend. In the Victorian era, women making starvation wages would twist flowers into pretty mussie tussies early each morning. A house preparing for a wedding would have servants doing nothing but fussing over the flowers. You have neither the experience or the time to do everything with perfect bows and bits of wire. Secondly, do a dry run. Make sure you know how fragile the stems of your target flowers are, and make a couple of bouquets and boutonnieres weeks before the wedding. Thirdly: delegate. People like working with flowers, and the result is almost always lovely. Reliable friends can be trusted at flower marts, florist are nice people who need to make money too, and a patient eight-year-old could make the ribbon orange blossom wreath. (Or course, you may want a focused task to center yourself before getting married. I sliced about fifty apples and it calmed me tremendously.) Lastly; by necessity, everything must be done incredibly close to the last minute- either the night before or the day of the wedding. Plan for this, and ask someone if they can sweep in if there's another crisis that demands your attention.
If you have questions, please comment on this post. I'll try to help in a timely fashion.