Steps in Transplanting Seedlings

We’ve just returned home to find a notice from our local community garden announcing a seedling planting party this weekend. Now the Farm is a big operation and it will take a party-sized crowd a couple days to get all the tomatoes, peppers, squash, cucumbers, and melons out of its greenhouse and into the ground. You may not need much help getting your seedlings outdoors and into the garden… or maybe you do. Either way there’s some transplanting principles to keep in mind.

One is hardening off. The plants that you’ve germinated in the warm indoors on heating mats and raised under lights aren’t used to the cool, windy conditions they’ll experience outdoors. Give them time to adapt by placing them in a cold frame or taking them out for a few hours each day letting them enjoy their first taste of the great outdoors in sheltered conditions.

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Another factor important to transplanting seedlings is timing. The days of last frost have pretty much come and gone… but not everywhere. You’ll also want your soil to begin drying if you’ve had a wet spring. We saw lots of flooded fields and gardens in northwest Iowa over Memorial Day and can only hope that the plants already in those gardens will survive. (Last year, those areas were suffering from drought.) Some places are having the opposite problem, with drought conditions persisting.

The time of day you plant can also be crucial. Try to set your plants out later in the afternoon so the sun doesn’t dry them out and otherwise punish them. Wind can also be hard on them and rob them of moisture. If it’s windy, wait. Or provide them some kind of windbreak. Inverted milk cartons cut in half and anchored an inch or two in the soil work well and provide a mini-greenhouse effect. But don’t let the windbreak fall on your fragile seedlings.

Liberal watering is important for newly planted seedlings. But you don’t want soil to be saturated before you put plants in. Extremely wet soil will compact around the newly planted roots and smother or break them. Watering should come after they’re in the ground. If your soil’s still extremely wet, wait until it’s workable.

Transplanting is also a good time to give your seedlings a little starter fertilizer. We like to give them a rush of fish and seaweed fertilizer, diluted to twice the recommended level. Too much fertilizer will shock vulnerable seedlings. Mixing a little compost into the planting hole is always a great idea.

How deep to plant? Depends on the plant. Most plants need to be set only slightly deeper than they were in their growing containers with the cotyledons (that first pair of embryonic leaves) above ground. Tomatoes are different. Plant them deeply with much of the stem below the soil, removing leaves and side shoots to facilitate the planting. The “hairs” along the stem will form thin roots and take up water giving your plant added nourishment.

Some gardeners recommend bending the stem portion that will grow underground (scroll down) so that it’s horizontal. The idea here is that with more of the root closer to the surface, the plant will absorb more heat and produce more quickly. We’ve never been able to determine if this actually works in the mostly cooler zones where we’ve gardened. Anyone having success with this method should comment and let us know… please.

If you’ve grown your seedlings in peat pot containers or other containers that can be planted pot and all, it’s a good idea to tear them or break them up a bit to give roots a place to grow through while the container disintegrates.  Never leave the tops of peat pots poking out from the soil… they’ll wick moisture away from your plants roots.

If you’ve raised plants in plastic containers, or purchased them that way, water them thoroughly before transplanting. To remove them from the container, invert the plant with your fingers on either side of the stem and shake gently to loosen the soil ball and have it slide from the container. If the soil around the transplant’s roots is compacted, it’s a good idea to gently loosen it with your thumbs before sticking it in the ground.

Don’t be afraid to pat down the soil gently around your plant once it’s in the ground. This will help it stay upright and give its roots something to anchor in. If your plants droop, don’t worry. If you’ve done well, they’ll be up and happy the next morning. For more detail on moving young plants outdoors go here and here.