The following 101, on seed starting (AKA starting plants from seed), features the combined wisdom of many (many) HOMEGROWN members. Got another tip to add? Post a comment below and spread the love!
Sure, starting plants from seed requires perseverance and dedication, but the payoff of watching those wee shoots sprout forth from the soil is huge. Insurmountable, even. (OK, maybe biting into the resulting fruit or veggie is a bigger deal—but not by much.) There are a few things to consider when starting seeds indoors, including which varieties of seeds to buy (check out the Selecting Seeds 101 for tips), the needs of each seed variety, the amount of time and germinating conditions of each variety, and a commitment from you to see them through. And patience. You’ll need patience.
When thinking about where to situate your indoor seed garden, keep in mind factors including pets, children, a source of natural light, and appropriate ambient temperature. You’ll need an area with a south-facing window, an average room temp between 65 and 70 degrees Fahrenheit, and a power source for artificial light.
Lots of folks opt for either "peat pots" or "peat pellets," although not all versions contain actual peat. These are those tiny biodegradable pots and miniature hockey pucks that, when it comes time to transplant your seedling, you can bury in a larger pot or plant in the ground, pot or pellet included. The benefit here is that, since you don't have to remove the delicate seedling from its container, you won't disturb its still-developing root system. Peat pots and peat pellets are great (for tips on what kind of planting medium to use in peat pots, keep reading!), but not all peat products are created equal. For starters, many varieties aren't organic, so if you're aiming for a sustainable, ecologically friendly garden—and especially if you're growing food—you'll want to read labels carefully.
Regardless of whether you use peat pots or peat pellets or nothing at all, you'll want to set (or plant, if you're going au naturel) your individual seedlings in a tray for ease of transporting. Especially if you're planting directly in the tray, without peat pots or pellets, you'll want to pick one similar to the version pictured at right, with cells to separate individual seedlings. Also important: Use clean trays with appropriately sized cells and holes in the bottom for proper drainage. Remember that some seed varieties, like pumpkins, require more room than others, like onions. You can purchase ready-made containers like the one in the photo at right, or you can make like HOMEGROWN member Andrea and repurpose yogurt cups and salad bar boxes into fully functioning seed flats. Fun!
POTTING SOIL VERSUS POTTING MIX
There’s dirt and then there’s dirt. Unfortunately, when it comes to starting seeds, you can’t scoop shovelfuls straight from the yard: The microorganisms in backyard—and even in many store-bought potting soils—can harm germinating seeds.
On that note, let's clear up a major question right here: What's the difference between "potting soil" and "potting mix" (sometimes called soilless mix)? Potting soil may have amendments in it (perlite, vermiculite, et cetera) but first and foremost: IT CONTAINS ACTUAL SOIL. Because potting soil can be dense and heavy, it can stay water logged, leading to root rot and restricted airflow. It's generally better for raised beds or in-ground planting than for container gardening. That said, a megathirsty plant that drinks a lot of water will like potting soil.
Potting mix, or soilless mix, is made up of things like perlite, vermiculite, possibly peat, possibly sphagnum moss, or possibly coir, but IT DOES NOT CONTAIN SOIL. Potting mix is especially popular as a growing medium for starting seeds. It drains well and allows air to flow while still retaining water, which makes it ideal for small container gardening. That said, it's not always black and white, and an experienced home gardener is nothing if not a chemist, mixing and remixing his or her formula.
But want an easy answer? When you're starting seeds, go for potting mix or
For more on potting soil versus potting mix, check out the Container Gardening 101.
PLANTING (AND TRANSPLANTING)
When sowing your seeds, fight the urge that more is better. Stick to just a few seeds per cell. You ultimately want one or two seedlings that are strong and healthy rather than a mess of weak sprouts vying to survive. Follow the individual seed packets’ instructions for number of seeds per cell and for planting depth. As seedlings grow, you’ll eventually transfer them to larger containers—or, eventually, into the ground—which makes labeling each cell vitally important. You have to know what’s what if you want to give your pups what they need! For oodles of tips on transplanting, don't miss the Transplanting 101.
En route to germination, most seeds need moderate light, rather than direct sunlight, for about eight to ten hours a day; refer to the seed packet for specific directions. Some seeds like a south-facing window; some require partial or full darkness; others need extra artificial light.
For most varieties, you’ll need to maintain a soil temperature of 80 to 85 degrees—a challenge in some parts of the country during winter or very early spring. Placing your containers on heating mats, under heat lamps, atop a refrigerator or another appliance, or covering your seed trays can help keep the soil warm.
Once your seeds have germinated and you’ve got sprouts poking above the soil, you’ll need to supplement ambient light with artificial help: Emerging seedlings require about 14 to 16 hours of light per day. Low-hanging fluorescent lights, often called grow lights, usually work. For ideas, check out Melissa’s DIY shop-light setup and Jaccqueline’s floor lamp outfitted with full-spectrum fluorescent bulbs.
Germinating seeds don’t require a lot of water. A daily mist should keep seed trays from drying out, and covering the seeds with a propagation dome—a.k.a. a clear plastic lid, like the one in the photo at right—will help hold in moisture. Just remember to remove the dome once your sprouts have emerged.
When your seedlings are strong and nearly ready for transplanting into the garden, it’s time to harden them off—basically, a process by which you introduce them to the outdoors gradually, for a few hours at a time. Incremental exposure to the elements—sun, wind, rain, your neighbor’s curious cat—will allow them to adjust to their environment and, ultimately, to thrive and survive climactic conditions. Start by moving your seedlings outside for three hours a day, then five, then eight to ten, and then overnight.
MORE SEED-STARTING RESOURCES
RELATED HOMEGROWN 101s
A few extra seeds to plant in your brain:
JOIN THE CONVERSATION!
Got a question? A tip to share? Post it below and keep the conversation alive and growing! Then troll for more things to plant, grow, cook, preserve, make, and craft in the HOMEGROWN 101 library.
PHOTOS, FROM TOP: (CLOSE-UP) PETE AND IZZY'S MOM; (PEAT PELLETS) JENNIFER; (PEAT POTS) ERIKA; (TOP VIEW OF SEED TRAY) MICHAEL; (TRAYS ON TABLE) PETE AND IZZY'S MOM; (SEEDLINGS UNDER GROW LIGHT) JULIE; (COVERED SEEDS UNDER GROW LIGHT) CARRIE
Here's a tip for those of us who want to put our starts out a little early:
Cut off the bottom from a "sport top" drink bottle and place it over tender seedlings. The bottle protects the seedlings from wind and critters, and the top serves as a release for excess heat. A mini greenhouse born from the recycling bin! Thanks to Julie for sharing this! Her full blog post about using sport top bottles can be found here.
Fluorescent lighting (particularly the new T-5 bulbs which triple the light output of normal fluorescent bulb without increasing the wattage) fulfills only part of the equation. In cold environments, like a chilly basement in a home situated above the frost line, it would be a good idea to place a heating pad underneath your seedling tray. Many gardening supply houses sell heating mats just for this purpose. Many plants, particularly warm weather veggies, accelerate their growth when the soil around their roots is warm.
Chris: Thanks for the ace tip. And presumably one can put the heating pad on a timer, too, so one (ahem, me) wouldn't go off and forget about it? Or am I living in the 1970s and thinking of a totally different type of heating pad?
Jennifer: You're welcome! Yes, I do mean a regular ol' fashioned heating pad, just like what drugstores have been selling for sore muscles since the 1970's. Despite the warning on the box (put there mainly so the company can avoid frivilous lawsuits) leaving it 24/7 isn't a problem for a lot of people. If it bothers you, then you can use a cheap hardwaare store timer.
A quick search using keywords "gardening heating pad germinating seeds" came up with a page from Chow Hound in which one person says he has "...used bottom heat for seed germination and early growing for some years for plants that like warm soil for germination" and that "if you use bottom heat for germination, cover your starting trays with clear plastic to hold in moisture and heat until the seeds come up." Another person there posted a handy chart that shows percentage and time for germination at various temperatures.
Good stuff. :)
Chris: Good stuff, indeed. Thanks for finding it and passing it along.