Your Grass Seed Bag is Lying to You

If you’re like me, you’ve made the mistake of thinking that everything in a bag of grass seed is in fact grass seed. Unfortunately, that’s not the case. A bag of grass seed doesn’t just contain the grass so beautifully displayed on its label but also a lot of undesirable material, including weed seed, crop seed, filler, and fertilizer. Just as important as what’s in the bag is how long it’s been sitting on the shelf. If that bag of seed has been hanging around for more than 12 months, then barely half of it will germinate. Luckily you can find everything you need to know right there on the label, so you can get the most out of your seeding effort. You just need to know where to look and how to interpret it.

Related: Never Plant This Grass Seed Type in the Spring

How to Read a Grass Seed Label Like a Pro

You’ll typically find the label on a bag of grass seed on the back near the bottom of the bag. Here’s what to look for and what each line means:

• Germination percentage: This is the percentage of pure grass seed that should germinate in ideal conditions. High quality grass seed typically has a germination rate of between 85% and 90%.
• Other Crop Seed: This mysterious term refers to all the seeds in the bag that aren’t the grass that’s on the label but still qualify as grass seed. This includes orchardgrass, clover, bentgrass, and timothy. Just because it’s not technically weed, doesn’t mean you want it in your lawn. I look for bags of grass that have as low a percentage as possible of crop seed, which is ideally 0.0% to 0.1%. Even just 0.5% of crop seed can fill your lawn with these undesirable grass types. 

• Weed seed: We all know what this is and none of us want it. Obviously, you want the percentage of weed seed to be as low as possible, but what’s acceptable? The best stuff is going to have exactly zero weed seed. Expect to see a tiny amount of weed seed in cheaper grass mixes, which is okay if you’re on a budget. Anything above 0.1% will create significant weed problems and simply isn’t worth your time or money. 

• Noxious weeds: These are the bane of your lawn’s existence. Noxious weeds include colorfully named seeds like Canada thistle, leafy spurge, bindweed, and quackgrass. Trust me, you don’t want any of these in your lawn. Most states require grass seed companies to list noxious weeds by name on the bag. If any at all are listed, put the bag back on the shelf.
  
• Inert matter: This is all the stuff in the bag that isn’t seed. It includes dirt, broken seeds, and seed coatings. Basically, this is the amount of dirt you’re paying for. A good quality grass seed should have less than 2% inert matter. There is one caveat: coated grass seeds. Coated grass seed has a fertilizer coating on each seed that helps it retain moisture. A bag of coated grass seed can have 50% or more of inert matter in the form of these fertilizer coatings. That means a 50-pound bag of coated seed might only have 25 to 30 pounds of actual seed in it and hence about half the coverage. While coated seed does have a higher germination rate, it’s not enough to account for the difference.
  
• Test Date: Bags of grass seed have test-by dates on them. Think of this as you would the expiration date on a gallon of milk. With grass seed, the further you get from the test date, the lower the germination rate. I recommend looking for a bag with a test date that’s within the last year, which should give you a solid 90% germination rate. Bags more than a year old will have a much lower germination rate that’s closer to 50%. 
  
  Pro Tip: Be especially wary of grass seed that’s on clearance. Check the test date carefully to make sure the retailer isn’t marking the seed down to get rid of last year’s inventory.