Garden Planning 101: Seed Starting

This post is a part of a series on planning your 2013 garden.  Click here to read all of the posts in this series.  

If you’ve been following this series of posts over the past month, you’ve already taken stock of your seed collection, selected the varieties you want to plant, and have developed a fruitful and functional garden plan, and now that we’ve come to the last post of the series, it’s time to get down to business and talk about getting started on growing your 2013 garden.

Whether you’ve already placed your seed order to get a head start on growing or are planning on hitting the local garden center when the weather warms up for just a few seed packets and plants, getting ready to plant is where things get real (and exciting!).  There is an art and a science to seed starting, but it all comes down to a few basic rules that are easy to follow.  Knowing the basics on when and how to start seeds will go a long way to ensure the success of your garden.

Know When to Plant ‘Em
Remember when I told you garden planning is all about location, location, location?  Here it comes back into play as the determining factor of when you should start planting your seeds.  Knowing your frost free dates will tell you not only when, but how to start your seeds.

There are two different ways to start seed:

  • Seeds can be direct sown, or planted directly (as the name suggests) into the garden soil as soon as conditions (soil temperature, risk of frost, etc.) are right.  Plants that should be direct sown are typically plants that do not like to have their roots disturbed once they start growing, like beans, peas, corn, leafy greens, and squash.  They are also plants that will easily grow to maturity in the window between the last and first frost.
  • When a plant takes a long time to germinate or needs more time to reach maturity than the window between frost dates, they are typically started indoors and transplanted into the garden when conditions are favorable. Vegetables like tomatoes, peppers, broccoli, and cabbage are all almost always started indoors, but other vegetables can be either direct sown or started indoors for a head start.

A good source of information on how and when to plant is the back of the seed packet, where you will find recommendations as to which method is best (or if both are an option), and will also give you the recommended number of weeks before last frost date to start seeds indoors.  It’s also a good idea to check a planting calendar or use an online garden planner that will generate a customized planting schedule.

The Right Set Up
If you are going to start seeds indoors, it’s important to have the right set up to give your seedlings the right conditions in which to grow and thrive.  A lot of seeds will germinate under less than ideal conditions, but without the right conditions, the quality of your seedlings will suffer.

  • Soil: The ideal soil for seed starting should be light and fine.  Bags of starter mix (a lighter blend than regular potting soil) are easy to find at garden centers or hardware stores.  You can also make your own starter mix by combining 4 parts compost, 2 parts peat moss or coir, 1 part perlite, and 1 part vermiculite.
  • Containers:  Seeds should be started in individual cells or pots to keep the roots from getting intertwined and potentially damaged when seedlings are separated for transplanting.  There are a lot of options for containers, from plastic cells to peat pots to DIY newspaper pots (and even no-container options, like soil blocks), all of which can be held in a large flat tray for watering and drainage.
  • Light: Seedlings need 12-16 hours of light a day.  Your best bet is to use a florescent light fixture with two “cool white” bulbs and position it right above the seedlings.  The light should be 2-4 inches from the plants, so hang the light above the seedlings with an adjustable chain so the light can be adjusted as the seedlings grow.  Using a timer to turn the light on and off automatically will help keep the light consistent and ennure that the plants also get the dark time necessary for proper growth.
  • Heat: Heat is an important element for germination, and some seeds, like pepper seeds in particular, need very warm soil to germinate and grow.  If at all possible, place your seed starting set up in an area that is free of drafts and outside walls or windows.  In addition, a heat mat underneath the tray can really give your seedlings a boost.  Heat mats can be purchased through most seed companies and garden centers (last year, I had good luck with a DIY heat mat using rope light).

Getting Started
Once you have everything you need to start your seeds indoors, it’s time to get started:

  • Planting Depth: Follow the recommended planting depth when you start your seeds.  Most seeds just need a light cover of starting mix, but some seeds, like peppers, do best when they are just left on the surface of the soil.
  • Covering: After seeds have been planted, covering the containers with a clear plastic dome will help germination by holding in moisture and heat (think mini-greenhouse).  Plastic wrap can work in a pinch as well, but just be sure to remove whatever cover you are using as soon as seeds germinate.
  • Watering:  Maintaining consistent moisture for seedlings is important–allowing seeds that have started to swell and germinate dry out can kill the germ and too much moisture can encourage damping off, a fungal condition that kills seedlings.  In order to avoid washing out seeds and tender seedlings, watering should be done indirectly, by adding water to the bottom of the tray. Using a spray bottle to mist seeds until they germinate is another effective way to ensure that your starts stay moist.
  • Feeding: Seedlings typically do not need extra fertilizing, as they are drawing their nutrients primarily from what is already stored in the seed.  If your starting mix contains organic matter like compost, it is usually enough to for the seedlings until it is time to transplant them into the garden.  If you do decide to give your seedlings a boost, be sure to wait until several sets of true leaves have developed and then use a highly diluted solution no more frequently than once a week.
  • Thinning: If you start more than one seed per container, eventually you will need to thin out your seedlings, keeping the strongest and healthiest plants.  I like to wait until at least one set of true leaves emerge, to get a better sense of which seedlings look best.  Rather than pull out the extra seedlings (and risk disrupting the root system of the seedling you want to keep),  just snip off the extra seedlings at the soil level.
  • Up-potting: To keep seedlings from becoming root bound, it may be necessary to move seedlings into larger containers before transplanting.  This can happen especially in particularly cold springs, when transplanting to the garden may be delayed.  Transfer the entire cell of soil into the larger container, taking care to disturb the roots as little as possible and adding additional soil as necessary.

As it gets closer to time to transplant the seedlings into the garden, there are some things you can do to make the transition easier on your tender vegetable plants (the same principles will apply to plants you purchase at a garden center to transplant into the garden).  For additional details, check out my post on transplanting from last spring.

  • Hardening off: Seedlings that are started indoors will need to be hardened off before they are put out in the elements for good.  By gradually increasing exposure to direct sun, wind, and cool night temperatures, the seedlings will grow stronger and more resilient.  Turning on a fan to create a light breeze in your seed starting area will help seedlings develop stronger stems and make the transition easier.
  • Timing: In general, once you are past your frost free date, it’s safe to move seedlings out into the garden.  Some more cold tolerant plants, like broccoli, can be moved out early and might even survive a light frost if they have been properly hardened off.  Once seedlings are in the garden, keep an eye on the forecast and take precautions when overnight temperatures get below 40 degrees.
  • Protection: To minimize the shock of transplanting, seedlings can be covered with a cloche (recycled milk jugs work well) to help regulate temperatures and provide extra wind protection until transplants become established.  Covering the seedlings can be especially helpful if the weather is cooler.
  • Watering: Seedlings should be well watered at the time of transplant and watered daily until the seedlings become established.  If seedlings are transplanted during a particularly hot stretch of weather, more frequent watering may be necessary.

Direct Sowing
When the time finally arrives to start direct sowing seeds in the garden, many of the same seed starting principles will be helpful to keep in mind.  Additionally, pay attention to these basics of direct sowing:

  • Soil Temperature: While your frost date is usually a safe guide for direct sowing, some seeds, like corn and cowpeas, may have specific requirements as to how warm the soil needs to be for germination.  Plant these seeds too early, and the seeds will rot instead of germinating. I usually plant my seeds in two rounds: cool season crops first (like greens, peas, radishes, brassicas, and onions) and warm season crops (beans, corn, cucurbits, and basil) a few weeks later.  Row covers can also be used to hep speed up the warming of the soil in spring.
  • Soil Preparation: Garden soil should be well worked before planting seeds in the garden.  Garden traffic from the previous year, winter precipitation, and spring freezing and thawing can compact the soil.  Working up the soil about a foot deep with a fork and working in some compost and manure will loosen up the soil for the seeds and prepare the soil for another growing season.
  • Watering: like seeds started indoors, seeds that are direct sown need consistent moisture while they germinate.  Use a light spray nozzle to keep the water from washing out the seeds and watch more carefully during hot stretches of weather.  The best time of day to water seeds and plants in the garden is early morning; avoid watering during the hottest part of the day.
  • Thinning: If the spacing of some of your seedlings are looking a little crowded after they have emerged, thinning may be necessary.  Again, it’s best to pinch off the seedlings that need to be removed, in order to leave the roots of the remaining seedlings undisturbed.  Trust me, I know how painful it is to remove seedlings, but your plants will produce much better if they have enough space to grow.  On the plus side, the seedlings you thin out will make a nice little microgreen salad!

So there you have it: all the basic information and resources you’ll need to plan and start growing your 2013 garden!  I hope you’ve enjoyed this series as much I have enjoyed working on it (and on that note, if there are other topics you’d like to see covered in a similar way, let me know).  Good luck and happy gardening!

2 thoughts on “Garden Planning 101: Seed Starting

  • March 23, 2014 at 10:24 pm

    Inspired by you, I’m growing Cayenne Peppers and some Heirloom Tomatoes… Among many, many other things.

    • March 29, 2014 at 11:13 am

      Awesome! Those are definitely two of my favorite things to grow. Looking forward to following along!


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