Transplanting Seedlings Outdoors

AT SOME POINT, YOU HAVE TO INTRODUCE your vegetable seedlings to the great outdoors. Transplanting seedlings is fraught with potential problems. Transplant shock, root damage, too warm or cold weather, rainy weather and many other potential problems can stunt your plants’ growth or worse. Here’s a step-by-step guide that will reduced the risk when transplanting your vegetable seedlings.

1. Measure soil temperature. Transplant seedlings only when the soil is within the appropriate temperature. You can learn more about measuring soil temperature at my article called Transplant at Proper Soil Temperature. If you don’t plan on using a soil thermometer, you can always guess when the soil temperature is right, and many plants have a wide range of temperatures that will work, but transplanting at the optimum soil temperature will go a long way to reducing transplant shock.

2. Harden off seedlings. A good time to begin hardening off plants is when you are measuring the soil temperature. Hardening off is the process of getting your seedlings used to the outside environment. Plants have to get use to all the outdoor elements, even the sun. It might be hard to believe, but plants (sort of) get sun burned when they haven’t had a chance to gradually build up exposure to direct sunlight.

Start by bringing your seedlings outside at the location where you are going plant them for an hour or so a day and, if you can afford the time it takes, gradually increase the time each day. Be sure that the weather is not too windy. It’s easy for wind to permanently damage seedlings that are not used to the great outdoors. I start off by putting them in a cold frame if the temperatures are too low or it is windy.

3. Smooth and weed the planting area. I like to do this a week or so in advance. Then water and let the weeds germinate. Then weed again. This greatly reduces the number of weeds. If you do this and cover with mulch, too, you will significantly reduce the number of weeds during the growing season.

4. Measure from the bottom of the roots to the beginning of the stem. This helps to ensure that you dig the hole to the proper depth. Remember to add depth if you are going to add soil amendments such as compost.

Note that celebrated vegetable grower Eliot Coleman does not add compost below two inches. He feels that plants do better this way because it more closely mimics natural growing conditions, where most of the organic matter is near the surface. This is another area where I could do it either way.

5. Dig your hole. If you’re going to add amendments, mix them into the bottom of the hole with dirt that you’ve removed from the hole. Make sure the bottom of the hole is reasonably level, so the plant will sit properly on the bottom.

6. Remove the pot. This may be the most difficult step. Ideally you are using paper pots or soil blocks. But most people are not. At this point, there’s no question that soil blocks make the process easier. They are best at air pruning roots, too.

When using paper pots, I take a sharp razor blade and cut the pots slightly in areas where I don’t see any roots. I do this to encourage the paper to break down in the ground. I’m careful not to disturb the roots and to make sure the root ball holds together, especially with things like cucumber seedlings which are sensitive to root disturbance.

If you are using Peat Pots,* you don’t have any perfect options. If you are working with a plant that doesn’t mind a little root manipulation, you can cut the peat pot off from the root ball. Some people just tear it off. Or you can leave it, but it will not break down enough so that it doesn’t hold the plant back at least somewhat. When I dig up plants that were planted with peat pots intact, I’ve seen evidence that the plant has been stunted because it had difficulty breaking through the pot. I believe it takes a lot of effort for the plant to break through.

If you are using peat refills, you must cut off the mesh that is holding the peat. The mesh does not break down. If the roots have grown enough to be intertwined in the mesh this could be fatal.

With regular plastic pots, you should turn the plant upside down and encourage the plant out of the pot, being careful to support the stem and root system when you slide it off. Hopefully your seedlings are not too root bound.

7. Plant. Place the seedling in the hole, add soil around the plant and press it in firmly, but no so firmly that all the air is squished out of the soil. If it is a big plant, you may want to add a little water as you fill in the sides of the hole so you will make sure that water reaches to all areas around the root ball.

8. Add support for the plant. It’s better to add your support structures (stakes, cages, etc.) before the roots begin to grow. This avoids damaging the roots when pressing stakes into the ground. Some people take a chance and add them later because it is easier and more convenient.

9. Top dress with compost. My experience has been that seedlings do much better if you can add compost on top of the soil around the plants. It may not seem like this will matter, but I’m sure it gives the plants a kick start.

10. Water deeply. At this point, it is very hard to water too much.

11. Mulch. It’s best to add mulch after you have watered so that the water reaches the right places. I put black and white newspaper down and cover it with mulched leaves after I’ve watered.

Below is a video that shows some of the finer points of transplanting tomato and pepper seedlings:

Do you have any pointers for transplanting seedlings. If you do, let us know by commenting below.

Related articles that might interest you:

1. Transplant at Proper Soil Temperature
2. Getting Rid of Gnats on Seedlings
3. Five Tips for Starting Seedlings More Cheaply
4. Don’t Use Compost Tea on Seedlings


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6 Responses to “Transplanting Seedlings Outdoors”

  1. April 12, 2011 at 11:08 pm #

    I just posted a comment on the grow light post but here would also be useful. in areas with crazy weather like in Nevada, beyond the steps above, use a wall of water. it protects you plant and gives it the extra temperature boost you need. Here is a quick blog on using a hula-hoop to amend your soil and a picture of using walls of water. Great post.

    • April 13, 2011 at 7:22 am #

      Cody — I now have a use for the old hula-hoop that my daughter no longer uses. I think it’s a great idea and will use it as a guide for when I plant my first tomatoes later this week.


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