I found these great tips on how to save money on wedding flowers on E-How
Use flowers that are in season. They're readily available and cost less than flowers that are out of season. And all flowers cost more during the month of February because of Valentine's Day.
Get married on a holiday when the church will already be decorated. Christmas and Easter decorations already set up in a church can make a beautiful backdrop for your wedding.
Shrink your bridal party and your guest list. Fewer people mean fewer bouquets and decorations.
Coordinate with another bride who is getting married around the same time as you. The two of you might be able to split the cost of flowers.
Look outdoors for decorations. An outdoor wedding can save you tons of money on flowers, because you can find a setting that is naturally beautiful.
Supplement large arrangements with less expensive flowers. Usually, these arrangements are far away, so your guests won't be able to tell anyway.
Create your own arrangements. You can use silk flowers or even flowers from your own garden. And you save a lot of money in the process.
Fill spaces with greenery instead of flowers. Large potted plants can be rented for significantly less than flowers. Ivy and other greenery is also beautiful as an accent.
Think about fruit and other alternative arrangements. A vase full of fruit is just as eye catching, and it's quite a bit cheaper.
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