The following 101, on transplanting seedlings outdoors, comes from Farm Aid’s farmer resource specialist, Jessie Deelo, a woman who knows her soil. Thanks so much for passing along your know-how, Jessie, and please keep the ideas blooming!
At this point, I’ve been in and out of the fields more times than I can remember. Before landing my job at Farm Aid last year, I worked on organic vegetable farms in Wisconsin, Colorado, Vermont, California, and Massachusetts. It took me 16 years to earn my 10 years of farming experience, but I got to work on some really cool projects along the way. I was a raw food chef in Berkeley, sold mushrooms at farmers markets around Chicago, inspected sunflowers for seed production in the Central Valley, and researched how farmers learn in Virginia.
I could attempt a very corny metaphor about being a transplant myself and draw connections about how the knowledge you need to prep your ground, get yourself settled, and thrive in a new environment relates to seedlings. Let’s skip that part and get to the good bits—practical info about transplanting into your garden. When it comes to planting your garden, there are two methods: direct seeding and transplanting. Direct seeding is planting seeds where they’ll ultimately be growing: outdoors, either in the ground or in raised beds or other containers, without starting them indoors first. Transplanting means replanting outdoors the seedling (that is, the young plant) that you either started indoors from seed or bought at your local farmers market or garden center. One important note: The tips in this 101 work whether you’re transplanting into the ground or into raised beds or other containers.
To decide when to transplant, it’s important to: 1) Know the projected final frost date for your area (try this handy tool from the Old Farmer’s Almanac); 2) Watch the weather; and 3) Play it safe. In Eastern Massachusetts, where I ran a 15-acre vegetable farm, we aimed to start planting our hardiest cold crops by April 15. Four out of five years, however, we planted a week late due to the weather. In the spring, night temperatures are more critical than daytime temps because the cold can stunt or kill your transplants. During the summer months, watch for high temps above 85F and try to avoid planting in extreme heat, as the seedlings are not able to absorb enough water to keep up with how much they’re losing. Most importantly, don’t get in a hurry. Your transplants will do better sitting in cold frames and getting a little root bound than struggling to survive near-freezing temps, hail, heavy rain storms, and countless other whims of Mother Nature.
The amount of time a seedling needs to grow on in the greenhouse or cold frame after the seed is first planted varies widely from species to species. Look for the particulars in your seed catalog. For example, tomatoes typically need four to five weeks from seed to transplanting. Lettuce is about three weeks. Alliums (the veggie family that includes onions, scallions, leeks, and garlic) take the longest, up to ten weeks. Whether you are growing your seedlings in a greenhouse, on a windowsill, or in a cold frame, the best practice is to go by the plant’s development of true leaves, which are the second set of leaves that appear. The first ones are cotyledons, or the baby leaves that look very similar for all plants. The true leaves look more like the leaves of the plant you are growing: tomatoes, broccoli, spinach, et cetera. When there are two sets of true leaves, your seedling is usually ready for transplanting. The leaves in the photo below? Those are cotyledons (on melon plants, for the record).
Before setting your seedlings out to transplant, you’ll want to harden them off for about two weeks. To be completely honest, I have transplanted directly from the greenhouse. Not best practice, but things happen. On the farm, we call these “experiments.” Here are some basic instructions on hardening off from the Seed Starting 101:
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.
And don’t forget to refer back to your seed catalog or those seed packets you carefully stashed away for plant-specific details. For example, celery and celeriac are hardened off by reducing water rather than by changing temperature.
Most folks recommend planting in the early morning or late afternoon. I greatly prefer to plant in the late afternoon because the plants can ease into their new home when conditions are the least stressful. Below are a few more transplanting tips and tricks I’ve picked up over the years.
1. Dig the right sized hole. For small plants, such as lettuce, spinach, and onions, you don’t even need to make a hole. Put your trowel in the prepped beds, pull the trowel toward you, and gently drop in the seedling on the far side of the trowel. Pat down the soil enough to keep the plant upright and firmly in the ground but don’t compact the soil around the plant.
2. Go deeper when you need to. For things such as tomatoes and cucurbit crops (the veggie family that includes cucumbers, squash, and melons), dig a hole about 6 to 8 inches deep and 3 inches wide. Throw in a small handful of compost—even if you have prepped your beds, this extra boost of nutrients decreases the stress of transplanting—and place the root ball firmly in the ground. These larger crops can be placed as deep as their true leaves, as they will grow roots all the way up their stems. Firmly pack the soil around the root ball. This is important, as air pockets around the roots create happy homes for fungus (and not the good kind).
3. Water before and after planting. It’s best to plant into moist soil so that the transplant doesn’t have to work too hard to reach water and nutrients. Avoiding any unnecessary stress in the first couple of days will allow the transplant to flourish more quickly. Before planting, add enough water to your bed so that the soil feels cool and wet but doesn’t stick to your hands. Fish emulsion decreases transplant stress, so it’s helpful to water your seedling with organic fish fertilizer before transplanting. (Neptune’s Harvest is available online, but your local independent garden center might carry other options.) Then give your beds a nice dose of water after planting. All of the water should soak into the soil after a couple of minutes. Avoid creating puddles that don’t drain, as these, too, can lead to fungus and bacteria.
4. Mounds versus wells is not important. Both mounds (building the dirt up around the base of the plant) and wells (creating a depression at the base) will be disturbed with weeding. The only plants that benefit from a buildup of soil around their base are leeks and scallions. Any part of those varieties that remains under the soil will stay white—highly edible—rather than turning green. Fun science fact: The chlorophyll, or what turns plants green, won’t be activated without exposure to sunlight.
5. Mulch. Mulch. Mulch. Need I say more?
6. Transplant everything—or at least try to. I’ve started all kinds of seeds indoors and then transplanted them as a way to get a head start on weather and pests. Some pleasant transplant surprises you might want to experiment with include beets, spinach, sweet corn, popcorn, cilantro, cucumbers, melons, and squash. Some things that have worked better for me as direct seeds, rather than transplants, include dill, peas, and carrots.
7. Buy a nail scrub brush. OK, maybe I’m one of the few who transplanted an acre of tomatoes the day before my wedding, but dish soap on a nailbrush works wonders for washing up when you need to be presentable after planting. Sugar scrubs are also very good at getting caked-on dirt off of your hard-working hands. Lavender sugar scrub 101? Yes, please!
8. Don’t worry about perfection. Remember to enjoy the process. Soon tomato juice will be dribbling down your chin, and it won’t matter if you forgot the fish emulsion. Dig in!
Got a question for Jessie? Or your own transplanting tip to share? Post it below and keep the conversation rolling! You might also be interested in related 101s on selecting seeds, seed starting, cold frames, companion planting, raised beds, container gardening, and composting. And don't miss Rachel's awesome blog post, full of tips specifically for planting tomatoes. You can find 101s on growing all kinds of crops, from asparagus to peas, as well as many more things to plant, grow, cook, preserve, make, craft, and tend, in the HOMEGROWN 101 library.
PHOTOS: (TOMATO SEEDLINGS) THE WHATLEYS; (JESSIE ON TRACTOR) JONATHAN MARTINEZ; (NASTURTIUM SEEDLINGS) DAVID; (SEEDLINGS IN GREENHOUSE) JONATHAN MARTINEZ; (COTYLEDONS) CARRIE; (TRUE LEAVES) CHRISTINA; (TOMATOES HARDENING OFF) JONATHAN MARTINEZ; (PLANTING BROCCOLI IN BED) M. SCOTT; (GROUP PLANTING) TODD; (SQUARE FOOT BED) JENNIFER; (MULCHED) GINNY; (LETTUCE IN FIELD) JONATHAN MARTINEZ