How to know how Many seeds to buy

by Deanna Williams

seeds packets

Once you have your growing area sketched out and sections blocked off for the different crops you want to grow, your next step is to calculate the number of plants you need to fill each row and determine the number of seeds to order. That might seem like a lot, and I think most of us can agree that math isn’t fun. But it’s easy to get in the groove, especially if you have consistent row lengths and spacing.

flower farmer Math

To calculate the number of plants you’ll need to fill a bed, all you really need to know is your plant spacing and the size of each row.

The formula I use is X = W * L * S

X : number of plants to fill the bed
W : width of row
L : length of row
S : number of plants per square foot

Below are the number of plants per square foot based on spacing:

6″ spacing = 3.5
9″ spacing = 1.63
12″ spacing = 1
18″ spacing = 0.5

Example: If I’m planting a row of zinnias in a 4-ft by 3-ft bed I would need….

X = 4 * 30 * 1.63

….196 plants to fill the bed.

But that doesn’t necessarily mean that I can get away with only buying 200 seeds. I err on the side of caution and plan for 80% germination rate. So I would want to sow at least 245 seeds. I get that number by simply dividing 196 by 80% (or 0.8). I start most of my seeds in 72-cell trays, so I would probably start 252 seeds and dedicate three and a half trays to that specific variety.

My favorite Seed Sources

  • Floret Flowers – everything your order from Erin you will fall in love with. Even flowers that you’re not too crazy about. There’s something in the varieties she offers and the way her and her team market their seeds. They find the magic in almost every variety and have wonderful quality seeds!
  • Johnny’s Seeds – they have an entire section dedicated to cut flower seeds on their website
  • Renee’s Garden – specialty varieties and seed packets beautiful enough to frame
  • Baker Creek Heirloom Seeds – huge variety of flowers and vegetables!
  • 3 Porch Farm – I get my money plant and sunflower seeds here every year
  • Swallowtail Garden – when I’m having trouble finding a certain variety, I always seem to find it here
  • Select Seeds – they have a lot of stock in flowers, fruits and vegetables!
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