To help your seedlings toughen up for their new life in the
outdoors, set them outside for a few hours every day. Make the
transition gradual. At first set them out only on sunny, calm days.
Bit by bit, build up their hardiness by putting them outdoors for
longer periods, during cooler days, and through warmer nights. After
a week or two they should be able to tough it out outdoors full
time.
2. Pick the Right Time
Obviously, you shouldn't transplant a tender annual when a cold
front is one day away. Just as important, pick the right time of day
for the big moving-out operation. Set the young plants out in the
late afternoon, early evening, or, best yet, during a spell of
cloudy weather. Why? Because transplanting is a shock to a plant's
system. Until its roots have settled in and gotten well established
in their new home, hot, dry weather can suck moisture out of the
leaves faster than the roots can replace it.
3. Water the Roots
Want to know a quick way to kill a plant? Let its roots dry out
(works every time). Since you don't want that to happen, water
seedlings well before you pull them out of their trays or flats.
Keep them wrapped in a damp cloth if they'll be sitting out in the
air before being dug in.
4. Dig
Make the hole wide enough to handle the full set of spread-out
roots. And make it deep enough so the plant's base will sit at the
same depth at which it has been growing.
5. Set the Plant in the Hole
Important: Handle the plant by the root-ball (best choice) or leaves
(second best), but not by that apparently obvious handle, the stem.
Leave it alone. The stem is the lifeline of the plant. And there's
only one. Injure it, you'll kill the plant.
Even if you have trouble getting the plant out of its pot, don't
pull on the stem. Turn the pot upside down and (holding the soil
ball) tap hard on the bottom of the container. You can gently poke a
stick through the drainage hole(s) to push the root ball out.
For roots that were tightly packed in their container ("root
bound"), tease them out a bit by hand to encourage them to spread.
Likewise, if the plant grew in a peat pot, lightly tear that pot to
help those roots start roving.
6. Water It Well
Plant roots need oxygen, but they absorb it from the soil, not
directly from the air. Air pockets left in the ground can injure or
kill exposed roots. So tamp the dirt firmly around the plant with
your hands and then water it thoroughly. Water will promote good
root-to-soil contact as well as help reduce the shock to the plant.
7. Shelter the Plant from Extreme Weather
Assuming you guessed right and the weather stays mild, you shouldn't
need to protect your transplant. But if the weather suddenly makes a
serious extreme turn, you may need to come to a seedling's temporary
defense. Cover tender plants when an unexpected frost is due.
Upside-down trash buckets or cardboard boxes, old blankets supported
by sticks (try to keep the cover from touching the plant), or a
thick mulch of loose hay may do the job. If a spell of blazing sun
hits right after you transplant, try to give the starts some form of
temporary shading.
That's pretty much it for the mechanics. The actual process, ah,
that goes much deeper. There's something so soothing, so bonding
about nestling seedlings in the soil that it may feel like you are
setting roots in the garden, as well as your plants.
