Since you know that your plants are available in 36 plants per flat you also know that at this spacing one flat of plants will cover 9 square feet. Therefore, calculate 215 (area to be covered) / 9 (area covered by one flat) = 23.88 flats required, round up to 24 flats.Click to see full answer. Likewise, how many plants come in a flat of flowers? Standard Flats They hold six six-packs of 2-inch starter plants or 12 six-packs of 1-inch starter plants.Beside above, what is a flat of flowers? A flat is a tray, usually plastic, made to facilitate watering and transporting groups of pots or plants. Some are simply large rectangular containers, while others may have small starter “cells.” Keeping this in consideration, what does a flat of annuals cost? I get the annuals for $10-$12 per flat from a local nursery. If the customer wants 10 or more flats planted I charge $10 per flat to plant them. If they want less than 10 flats the price jumps to $15 per flat.How much does it cost to plant flowers?To get an average of what it would cost to plant annuals in your beds, you can use a rate of $12 per square foot. This is just an estimate and can vary greatly depending on several factors, but this should get you in the ballpark.