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ASK MARTHA: Seed Starting - Part One Indoors

Growing your own plants from seed is the most rewarding, most economical way to create the garden of your dreams. Martha Stewart shares her secrets for success in this two–part article.

Question: Hi Martha, I’d like to grow from seeds – how do I start? 

Martha: I’m always asked what my favorite time of year is, and everyone thinks it will be one of the fall holidays. Actually, spring is right at the top of my list, and the germination of spring’s first seeds is one of the most exciting moments of the gardening year for me. No matter how many times I watch this process happen, it always feels brand new. As that delicate green finger pops up through the surface of the soil, I feel the same thrill I felt as a young girl, watching the very first seedling emerge from a cut-off milk carton my father and I had carefully filled with dirt, planted with thoughtfully selected seeds, and set out in our sunny kitchen.

And you can enjoy this magical spring garden experience too. Take any healthy seed, satisfy its simple requirements, and from it emerges a whole new life.  

How to start? Follow my informative guide below and get growing! 

DESIGNED TO GROW 

These days, I meet many gardeners who say they can’t be bothered with starting from seed. They’re convinced that the process is complicated and demanding—that too many things can go wrong. But they’re ignoring an essential fact of life that I learned from my father: Nature designed seeds to grow. Raising seedlings is a process at which anyone can succeed by applying a few easily learned skills.

There are many practical advantages to starting plants from seed. To begin with, it saves money. Become your own nurseryman, and you can raise a whole garden full of flowers and vegetables for the price of a few packs of seeds. 

More importantly, starting from seed is a fun and inexpensive way to experiment in the garden, allowing your entrée into the intriguing world of heirloom plants. You can’t really reproduce the rich flavor of your grandmother’s sun-dried tomatoes, say, unless you start with the same fruits she did, the ‘Principe Borghese’ tomatoes whose seeds she brought from Italy. You won’t find them as off-the-shelf seedlings at the garden center. You’ll have to do as Grandmother did and start those heirlooms from seed.

Equally rewarding varieties of almost every flower, herb, and vegetable are yours to discover—and along the way, you may even encourage the interest of a son or daughter, or a grandchild. Children are quick to grasp the magic that is in a seed. Plant one together, and you’ll be giving them an experience they can enjoy, year after year, for the rest of their lives. I’m constantly experimenting with flowers and vegetables that are new to me, but I always leave room for a few of the same hybrid columbines and ‘Big Boy’ tomatoes that my father proudly grew from seed in his yard in New Jersey.

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SHOPPING FOR SEEDS

All seeds are not equal. The success of any sowing depends on the quality of the seed you start with. Freshness is critical. The viability of seeds (the reliability of their germination) dwindles with age. Even the best-quality seed may not be very good if it has been sitting on a shelf for a year or two.

This potential varies from species to species. Onion and parsley seeds, for example, lose their viability quickly, within a year or so of being packaged; cucumber and spinach seeds may stay viable for five years or more if they are properly stored. To be safe, buy seeds from a supplier you know and trust and purchase only seeds packed for the present growing season. The year for which seeds were packed should be printed clearly on the packet. For the same reasons, be careful of where you buy seeds. Your best assurance of good quality is to buy seeds from a supplier you know and trust.

There’s a mine of useful information printed on most seed packets. In addition to giving instructions for growing the plant, the packet will help you decide whether a particular variety suits your needs and whether you want to grow that plant at all. The problem is much of this information is written in a kind of horticultural shorthand. The following Seed Packet Translator will enable you to decipher any packet. Download now!

STARTING SEEDS INDOORS 

Why bother? It might seem simpler, and easier, just to plant your seeds directly into the garden where they are to grow, rather than sowing them into pots indoors. Of course, it is easier to plant seeds right into the ground (this is called direct sowing). But it doesn’t always work. Many of the flowers and vegetables we’ve come to regard as fixtures are exotic visitors from other regions with distinctly different climates. Peppers, tomatoes, and petunias, for example, originated in warmer climates, and their seeds won’t germinate in the chilly soil of the spring most North Americans experience. If we wait until the soil has warmed before we sow these plants, the seeds will germinate, but there will not be enough warm days left in the growing season for the resulting plants to bear flowers and fruit before an autumn frost cuts them down. To give these plants the prolonged stretch of warm weather they require to mature, we must sow their seeds indoors. Here are some helpful instructions:

STEP ONE

Start with a soilless mix, such as Miracle-Gro® Seed Starting Potting Mix which should be light (to give the seeds air), porous (to absorb moisture but also to drain well), and sterile (to preclude disease).

You’ll also need:

  • Reusable individual plastic containers, or seed trays, cleaned and sterilized with a 1:10 bleach-and-water mix, and with holes in the bottom for drainage
  • Seeds
  • Labels

STEP TWO

Prepare the mix for planting. Combine it with warm water in a large bowl as needed until it is neither sopping wet nor dry and crumbly; if you squeeze it in your fist, it should hold together, but no water should run out. Fill each container, or section of the seed trays, tamp the mix down and then continue adding and gently tamping until the mix is almost level with the top of the container or tray cells. Seed starting trays are available in all sizes and formations. Select the right kind of tray based on the size of the seeds. The containers should be at least two inches deep and have adequate drainage holes. These can be saved from year to year, so don’t throw them away after the season.

STEP THREE

Now you are ready to plant the seeds. Large seeds should be planted no more than an inch apart and an inch deep. The rule of thumb is to plant seeds twice as deep as the seeds’ size. Use your finger or a pencil to make shallow holes, put in the seeds, and cover lightly with soil mix. Medium seeds should be a half inch apart and a half inch deep. The smallest seeds should be thinly scattered on the surface into furrows made with a pencil or ruler—and very lightly covered. Some are not covered at all because they need light to germinate; the packets will tell you which.

STEP FOUR

Label each pot or section, cover the surface with a thin layer soil mixture and water, using a spray bottle. Be gentle; you don’t want to wash the seeds away, and always use room-temperature water. Place the pots in a large bin or on trays so you can bottom-water thoroughly to encourage root development. Remove the pots and let them drain excess water to avoid fungus. Check the pots regularly; the seeds must never dry out.

STEP FIVE

Cover the pots or trays to increase humidity. You can use one big cover or a sheet of plastic wrap, or cover each individual pot with a clear top, such as a resealable plastic bag. Don’t seal the top completely; the germinating seeds need fresh air. Provide general warmth with a heating mat (sold at garden centers) if you can.

STEP SIX

Soon after the seeds sprout, remove the covers and place 40-watt fluorescent lights 2 to 4 inches from the top of the plants, adjusting the height as the seedlings grow. Leave the lights on for 12 to 14 hours daily; a timer is helpful. Fertilize when the first leaves appear, using a mix at one-quarter the regular strength; Miracle-Gro® Quick Start Planting & Transplant Starting Solution.

STEP SEVEN

When seedlings look sturdy and crowded, it’s time to prick them out: Gently knock the little clumps out of their pots and drop the ball of soil on a tabletop to separate the seedlings.

STEP EIGHT

Now you’re ready to transplant, to give each seedling more space. Use a general-use potting mix, such as Miracle-Gro® Indoor Potting Mix. Make holes with a pencil or small dibber, place the plants in the holes, holding onto the leaves rather than the delicate stems and keeping as much mix as possible attached to the roots, then gently firm the soil around them before watering, as carefully as before.

STEP NINE

To encourage branching and bushiness, certain plants, for example, zinnias, salvias, and cosmos benefit if you pinch off their growing tips just above the top set of leaves. Your thumb and forefinger are your best tools.

TRANSPLANTING

Even a well-grown seedling can’t stand an abrupt transition. To acclimatize your plants, you need to give them small doses of the wind, direct sun, and fluctuations in temperature they will encounter outdoors, a process called “hardening off.” At the appointed time before or after the last frost date, take the containers out daily—for a longer time each day—to a sheltered spot, and then bring them back indoors. After hardening off seedlings for a week or two, you can plant them in soil that’s aerated and workable. Make a hole for each plant, then, carefully holding the plant by the root ball, set it in its new home and water it in.

Article by Martha Stewart, as part of the Growing with Martha Stewart partnership.