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The Flower Show

Sowing Spring Seeds: A Gardener’s Guide to Planting Crop Seeds

March 14, 2024

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By Sally McCabe, PHS Associate Director of Community Education

While we find ourselves in the midst of winter, many gardeners are eagerly planning when they can get seeds in the ground again. Thankfully, there are several crop seeds that can be sown in the ground as soon as soil is workable. Other varieties can be sown after the last frost, and if you just can’t wait to get your seeds started, other crops can be started indoors.   

How To Read Seed Packs  

 Just about everything you need to know about planting your seeds will be on the seed pack. Grab one and read along with me:  

  • Days to emerge refers to when you will first see a plant breaking out of the ground.  
  • Seed depth refers to how much soil should be on top of the seed when you plant it.  
  • Seed spacing provides a recommendation for how far apart seeds should be planted from each other.  
  • Days to maturity refers to how long it takes to have a harvestable product.  

Lastly, the sowing instructions section on a seed pack will typically provide additional directions for planting, as well as special tips and tricks.  

Some packets also have a picture of what the baby plant will look like, so you can tell it apart from the weeds. ALL packets are required to have a sell-by date or at least a “packed for 20__” date. Newer seeds are best, but some last many years if taken care of (i.e., not left loose in your damp basement, or in the trunk of your car.)  

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How to Make the Most of Your Seeds 

Most of us have packets or half-packets of seeds left over from last year -- or even several years. Here’s a simple test to see if they’re still good: Spread out ten seeds on a moist (not wet) paper towel and roll it into the shape of a tube. Stuff that tube in a plastic bag and put the bag in a warm (not hot) place out of the sun. Unroll after a week and see if there’s any action. If not, give it a few more days. If more than half the seeds have sprouted, you can get away with using them. If there are less, try to find newer seeds.   

Another option to make use of half-full seed packs is to trade with other gardeners. Or plan ahead and agree before you buy them to split a particular envelope of seeds. Succession planting is also a great strategy. Succession planting refers to planting a row of something like lettuce now, another in two weeks, and another in two more weeks, etc., so you constantly have a new crop coming up while the last one is maturing. This will use up a pack of seeds over the course of the season.  

Alternatively, to save seeds from one year to the next, keep them sealed, and in a cool, dark place -- again, not in the trunk of your car.  

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Sowing Seeds Outdoors 

The first category includes seeds sown directly in the ground before the last frost. This category can also be regarded as ASASCBW — As Soon as Soil Can Be Worked! Seeds that can be sown directly into the ground before the last frost include peas, lettuce, beets, spinach, turnips, and most greens. These go in my garden bucket now, ready at a moment’s notice to go in the ground.  

The second category includes seeds sown directly in the ground after the last frost. This category includes beans, squash, and basil – these seeds get locked in the closet, so I’m not tempted.  

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Sowing Seeds Indoors   

If you’re eager to get seeds started now, tomatoes, peppers, cauliflower, celery, and cabbage can all be started indoors and transferred into the ground later. Personally, most of these seeds get shared out, because I can’t be bothered, and my friends do a really good job of this.   

When that actual “last frost” happens is open to interpretation. According to USDA, Philadelphia is now a solid Hardiness Zone 7B in the city near all the heat-holding buildings and paving, and 7A in the outreaches and surrounding neighborhoods. Also, per USDA, our average last frost is now around April 15. But combing through the Franklin Institute’s weather records for the last few decades shows that it rarely goes below 30 after April 1st. This means you have my permission to start planting cool season seeds anytime the ground is thawed, not covered with snow, and not too muddy. And, as a quick tip -- don’t bother growing vegetables you don’t like. Grow only what you want to eat!  

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What You Can Plant Now  

Crops that don’t care about cool night temperatures and a chance of frost include greens like mustards, lettuce, spinach, arugula, and kale, root crops like carrots, turnips, beets, radishes, and rutabaga, peas; transplant or roots include onion sets, potatoes, leeks, onion plants, cabbage, broccoli, cauliflower, collards, celery, or herbs other than basil.   

With these varieties and timelines in mind, you’ll be able to get your growing started as soon as possible, and will set your garden up for success this Spring! 

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