STC Plant Growth and Development
Lesson 4: Thinning and
Transplanting
(Day 4 or 5)
Kennewick School District
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Materials list
For each student:
 Student notebook
 1 toothpick
 1 pair of scissors
For every 2 students:
 1 hand lens
 1 pair of forceps
(optional)
For the class
Potting mix
Surplus planter quads
1 large or several small containers for the class plot (egg
cartons, milk cartons cut lengthwise, margarine tubs)
Wicks for above containers (if none available, use cotton
twine)
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Have you ever had experience
thinning or transplanting plants?
Why is it important to thin
plants?
Why is it sometimes necessary to
transplant plants?
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Observe your plant with a hand
lens.
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
How are the plants different from
one another?




Are all the seedlings the same size?
The same color?
Where are the differences, exactly? In the
shape or size of the leaf? In the length of
the stem?
Did every seed sprout, or germinate?
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Decide which one plant from
each cell you will keep and
which one you will thin out.
You will end up with four plants,
one per cell.
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Thinning and Transplanting
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Before thinning…

Gently loosen the soil with a toothpick.

Plan to set aside one of the extra seedlings
to draw later.
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
You may thin your plants by…


Cutting them close to
the soil and
discarding them.
or
Uprooting the plants
and transplanting
them.
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
If you choose to uproot your
seedlings you have the following
choices:



Transplant then into one of their own cells
where no seeds germinated.
Donate them to a classmate for
transplanting.
Transplant them into the prepared class
pots.
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Draw and label the parts of one
of your uprooted plants in your
science notebook.
Be sure to include:


The seed leaves, the stem and the roots.
Today’s date and the age of your seedling
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Add this vocabulary word and its meaning to your glossary.
seed leaves
The first two leaves that appear on a
plant after germination.
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Add this vocabulary word and its meaning to your glossary.
germinate
To start to grow from a seed into a
new individual.
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Clean up. Throw away any
plants you can’t use and return
equipment to their containers.
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Discussion

Even though the seedlings are exactly the
same age, how were the plants different?

You are all about the same age. How are
you different from one another?
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
Discussion

What are the requirements for plant
growth?

What are the optimum conditions for plant
growth?

What are the differences between the bean
seed embryo and the Brassica seedling?
STC Plant Growth and Development
Lesson 4: Thinning and Transplanting
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STC Plant Growth and Development Lesson 4