Sweet peas are among my favorite annuals planted
from seed in the fall. Extremely hard winters are a disaster
for sweet peas because they depend on winters that are relatively
mild. Sweet peas will take a freeze even into the mid-20's,
particularly if you mulch them on those few cold nights, but
cold winter temperatures can kill plants. If you want to be
absolutely certain that an unusually cold winter will not
destroy your sweet peas, wait until late December or early
January to plant seed.
Adventurous types can plant sweet peas now. In most years,
sweet peas planted now will be magnificent in the spring.
The best recommendation for growing sweet peas is to find
a good location. The best place is on the south side of the
house where the plants will get plenty of sun and a little
protection from cold winter winds.
Most sweet peas need a trellis but there are also dwarf
forms. If you don't have a chain link fence to support sweet
peas on-one of the best possible reasons for owning such a
monstrosity-you might try growing sweet peas on last summer's
Now, back to the soil preparation! One of the most common
recommendations is to dig a trench 24 inches deep and a foot
or more wide, placing several inches of manure in the bottom
of the trench and then mixing the soil dug out of the trench
with an equal amount of compost and at least 1 pound of Superphosphate
(0?20?0) per 100 feet of row. That translates to about 1 tablespoon
per 2 feet. This trenched area should end up 6 to 8 inches
above the surrounding soil to ensure good drainage.
There are several varieties of sweet peas. The early multi-flora
variety is readily available on most seed racks and is the
best to use for ornamental use since it produces several blooms
with short stems in each cluster. If you are interested in
using the sweet pea as a cut flower with a long stem, you
should plant the Cuthbertson variety.
Getting the seed to come up is another trick. The seed is
quite hard and may not germinate if you just plant directly
in soil without the next step.
Take a small file and carefully file through the outer seed
coat just enough to allow moisture uptake. Then soak the seed
overnight in warm water. By morning they should have swelled
considerably, telling you that germination will be rapid.
Since sweet peas are legumes, they also benefit from inoculation
with Rhizobium bacteria. The standard garden-packet type such
as nitrogen usually contains a portion of the sweet pea strain
of bacterium. Simply dust this material onto the damp seed.
There also is a granular form that you can sprinkle along
in the planting row. Sweet pea plants are heavy feeders, and
sprinkling bone meal, blood meal, or even a commercial fertilizer
like 12-24-12 some 6 to 12 inches from the base of the plants
through the winter will be important to keep them growing
In the spring, when they begin to bloom, don't hesitate
to cut the flowers since the more you cut them the more flowers
you can expect to see. As temperatures warm up later in the
spring, anticipate powdery mildew and spray at least a couple
of times with Ortho Funginex or Greenlight FungAway to prolong
their growth. Eventually, hot temperatures will take them
out anyway, but you should be able to extend the blooming
season with this treatment.
To compliment your sweet peas, you might plant dianthus,
pansies or Johnny Jump-Ups (pinks, carnations, etc.) as foreground
plants. Other winter annuals such as ornamental kale and cabbage
or petunias can also be used.