Indoors and Transplanting
Technique Tips with
Photos print version
When to start:
In cold winter areas, sow in seed starting containers in
early spring about 6-7 weeks before the last frost date, then plant out as soon as soil can be worked; sweet peas
can handle light frosts.
In mild winter climates, where the ground does not freeze,
sweet pea seeds can be fall-sown directly into the garden
from September through November to grow strong root systems
and then bloom in spring.
But if you don't get your sweet
peas planted in fall, you can still get a nice crop,
although a little later to bloom, if you give your seeds a
head start by sowing indoors in seed containers in late
January thru March to transplant into the garden as soon as
soil can be worked; sweet peas can handle light frosts.
Click on photo for larger view
may choose to nick your sweet pea seeds before planting.
Nicking the seed with a nail clipper breaks the outer coat of
the seed so it can absorb water immediately. By doing this a
larger percentage of your seeds will germinate and they will
sprout a few days earlier.
Here's how: Hold a seed between your thumb and forefinger. With
the other hand, hold the clippers at an angle so that you use
one end of the blade, then clip your seed. Your goal is to make
a slice through the brown top coat of the seed, not to take a
chunk out. Sometimes you can barely see the nick you made and
sometimes a piece of the seed coat cracks off and you see the
lighter colored inner seed. Both are correct!
When planting sweet peas in containers, do not
use garden soil. Instead, use a good quality potting mix.
Potting mix recipes are formulated to perform in the conditions
present in a small container, whereas using garden soil can
result in problems such as compaction and poor drainage. Many
soil mix brands are readily available at garden centers.
Always pre-moisten your potting mix before filling your
container. In a bucket or wheelbarrow, slowly add water while
mixing the soil to make it evenly moist. You are done when it
feels as wet as a wrung out sponge.
A 3-4 in. pot is a good size for starting sweet peas. If you are
re-using a pot, be sure to thoroughly clean it first to avoid
transmitting disease to your new soil mix. Fill the pot with
your pre-moistened mix and then lightly tap it on your work
surface to settle the soil. The soil surface of a properly
filled pot will be about 1 in. from the top of your container.
are now ready to sow your seeds. How deep you plant
them makes a difference. Always follow the planting
depth instructions on the back of your packet. For
sweet peas, make a 1 deep hole. Your finger or a
pencil works well for this.
your seed into the hole you made. We recommend sowing 2
seeds per pot so that, in the end, every pot has a plant
even if one does not germinate or dies.
If you choose to sow 2 seeds per pot, you will need to
thin to 1 seedling per pot after the first leaves have
formed. Cut or pinch out the extra seedling at the soil
line. Do not pull it out as this can disturb the roots
of the remaining seedling.
sowing, cover your seed with soil mix. We recommend labeling
your containers with the variety and date so you can keep track
of what you planted and when.
Gently water your covered seeds. Use a watering can or
hose with an attachment that diffuses the water so that
it sprinkles like a gentle rain. This will prevent the
water from washing away the soil or causing too much
While waiting for your seedlings to emerge, provide the
appropriate conditions for germination to take place.
Water and temperature are the most important factors.
Your soil should stay constantly moist, but not soggy.
The soil temperature should be between 55-70 F. If the
weather conditions permit, you can start your seeds
outdoors. Otherwise you will need to start them inside
your house or a greenhouse. If starting them outside,
provide protection from birds, snails and slugs.
After your seeds have sprouted, you must provide them
with a good source of light. Indoors you can place them
by a window as long as they will not experience extreme
heat from the sun during the day. Cooler night
temperatures by a window are not a problem for sweet
peas. You can also use fluorescent lights. However,
plants should be about 6- 12 in. from the lights for the
intensity to be bright enough.
you started your seeds inside, you will need to harden
off the seedlings before transplanting them into your
garden. Hardening off means gradually acclimating your
plants to the conditions they will encounter
outside--direct sunlight and temperature being the most
critical. If you do not do this, your seedlings may
suffer transplant shock after you plant them into the
Start the process of hardening off when your plants have
about 3-4 pairs of leaves. Move your plants to a
location outside that gets direct morning sun and
afternoon shade. If you do not have such a location,
each day you will need to move your plants into the sun
in the morning and out of the sun in the afternoon.
After about 3-4 days move them to a spot where they will
get direct sun all day. In a few more days you can
transplant them into your garden.
When your seedlings have 3-4 pairs of leaves, you can
pinch or cut off the top of the seedling, leaving 2-3
pairs of leaves. You should make your cut just above a
pair of leaves. Pinching gives you a fuller plant by
promoting lateral branching.
Sweet peas need well-drained, fertile soil, so before
planting add some aged manure or other finished compost
into your garden bed, work it into the soil, and rake
the bed to create a fairly level surface.
To transplant your seedling, dig a hole deep and wide
enough to fit the root ball.
removing your sweet pea seedlings from their container,
avoid disturbing the roots as much as possible. Try
this. To catch the root ball, put one hand over the top
of the pot with the seedling between your fingers, then
turn the pot over. With the other hand squeeze the sides
of the pot and then gently tap the bottom until the
plant and soil come out.
Place your seedling into the hole you dug and back fill
it with soil. It is important that sweet peas are
transplanted so that the soil level is the same as it
was in the pot. If you bury too much of the stem, the
plants may become diseased and stunted, perhaps even
your transplants 5-6 apart. Proper spacing between
plants is critical for the health of your mature sweet
peas. It improves air circulation to help prevent
disease and gives the roots of individual plants enough
space to forage for water and nutrients.
soon as you are finished transplanting, gently water in
your seedlings. This not only provides water to the
plant, but also settles the garden soil around the root
ball so there are not large pockets of air that can dry
out roots. Use a watering can or a hose with an
attachment that diffuses the water so that it sprinkles
like a gentle rain--this will prevent the water from
washing away the soil or battering your delicate
Tall sweet peas need a well-anchored support to climb
up. Erect one now so that it will be in place as soon as
your seedlings are ready to start climbing.
is critical to protect your sweet pea seedlings from
birds, snails and slugs. This should be done right after
sowing your seed, otherwise these common predators may
find your sprouts and eat them before you even know they
For birds, use netting. We make our own support hoops
from flexible, black plastic irrigation tubing, commonly
called polytube, and available at most good garden
centers. Cut it in lengths appropriate for the width of
your garden beds. Push the ends of the cut tubing into
the soil to form arches over your sweet pea bed. Drape
the bird netting over these arches and secure all edges,
making sure there are no openings. Remove the netting
before your sweet peas get tall enough to attach
themselves to it. For snails and slugs, we like the
product Sluggo because it is non-toxic to humans, pets
As your plants get taller and start to climb, you may
want to help wayward branches find their vertical
support system. Gently coax them onto your support.
Sweet pea branches snap easily.
keep your sweet pea plants blooming as long as possible,
we recommend deadheading. This means cutting off spent
flowers before they have a chance to divert energy
towards making seeds instead of more flowers. The ideal
time to deadhead is just after the bloom has peaked and
is just beginning to fade. Always cut off the entire
This plant has entirely finished blooming. As you can
see, the spent flowers form seedpods and the plants
slow down and then stop blooming altogether. Eventually, all
sweet pea plants come to the end of their flowering life whether
you deadhead or not, but you can prolong the bloom period by
cutting off spent flowers.
Of course the whole point of growing sweet peas is the
flowers. Don't forget to cut and bring them into the
house regularly. They make beautiful, exquisitely
scented bouquets. And the more flowers you cut, the more
the plant will produce!
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