Lathyrus


 

Common name: Sweet Pea


Lathyrus odoratus the sweet pea, was introduced to the UK around 1700.

They are primarily grown for their scented flowers, although they have been a favoured subject for exhibiting since the early 1900's when the National Sweet Pea Society was formed.



Harlequin
Mixed Spencer Varieties
Jimmy Shand

There are literally hundreds of varieties available to the general public with many new varieties being bred each year,here are some unamed varieties:





Cultivation


Sweet Peas require a rich, well cultivated soil.

For best results incorporate plenty of well rotted organic manure into the soil before sowing / planting.


Watering:


They should never lack for water during the growing season.

Mulch beds to conserve moisture.


Feeding:


Commence feeding plants with general liquid feed when they are about 600mm (24”) tall (Week 27)

As the plants grow, they will need trellis, canes, wire netting, etc. to support them.

Normally they do not need to be tied in.

However the real sweet pea enthusiast will remove the tendrils as they appear, and tie the stems in with plant rings or twist ties to divert the plants energy to producing more / better flowers.


 
Various stages of growth from planting out time until flowering.

Pests and Diseases:


Watch out for pests and diseases, for example;

Powdery mildew this is quite a common problem, caused by dry conditions around the roots and poor airflow around the plants.

To prevent the spread of this fungal disease, avoid wetting foliage, and spray with an appropriate fungicide at the manufacturers recommended rates.

Sweet peas are prone to viruses.

Viruses can be carried within the seed, even if only one seed in a batch is infected with a virus, aphids can quickly spread the problem to other plants after germination.

Virus-infected plants are best removed and destroyed.


Aftercare:


Cut and pick flowers as soon as they open, this encourages further flowering.


 
Various arrangements of cut flowers

You may find pollen beetles gathering in the blooms, they are quite harmless but can be a bit of a nuisance.

As there is no chemical control for them, try placing vases of affected flowers into a darkened room, with a light source at one end, you will find the beetles will be attracted from the flowers to the light.


Propagation:


There are a few ways to propagate Sweet Peas, for example:;


Directly into the garden:


Prepare the soil by raking it until a fine crumbly surface layer (tilth) is achieved.

Sow the seeds during April/May, (Weeks 14-18) individually at a depth of about 12mm (½”) and 225mm (9") apart.


Soil raked to a fine tilth
Form drill in soil
Water drill before sowing seed

Under glass:


For an early start sow from January to March indoors. (Weeks 1-10)

Sweet pea seed shells are quite hard, this can hinder moisture penetration into the seed, without which, the seed will not germinate.

A number of things can be done in advance of sowing to alleviate this problem, e.g.

Nick the seed shell with a knife or, abrade the shell with a piece of sand paper or,

Soak the seeds in water for up twenty four hours to soften the shell or,

Chit the seeds on the surface of moist kitchen towel, or chit them on top of the compost.

The choice is yours!


Lathyrus seed
Nick seed
Soak Seed
Chit Seed

Sowing:


Fill a cell tray*, pot or shallow box with good quality seed compost.

Sow the seeds about 12mm (½”) deep or sow 2-3 seeds in 100mm (4”) pots / boxes of seed compost.

The seeds should be kept at a temperature of 16°- 18°C (60°-65°F)

*Sowing in Cell trays ensure that the roots of the new seedlings to not become entwined which makes it easier to prickout / pot on.

Germination should take five to seven days.

When seedlings or plug plants are large enough to handle prick them out into 75mm (3") pots.


Clean Empty Container
Cells loosely filled with seed compost
Tap tray on bench to compact compost
Water compost (see below)

Tray ready to receive seed
Sow seed -one per cell
Seeds sown
Water if not done previously

Alternatively Cover seeds
Trays in propagator
Seeds germinated
Seeds germinated

Alternatively, one can use Root-Trainer pots from the outset, and there will be no need to prickout/pot on as you would with the other methods described.


Signs of Germination
Seeds Germinated
Seedlings hardening off
Seedlings ready for planting out

Sweet pea seedlings can become leggy if their growing conditions are too warm.

They should be grown in cool but frost-free conditions.

Check that they do not become pot bound prior to planting out.

If necessary pot up into larger pots.

Gradually acclimatise the young plants to the outside temperature, by using a cold frame or cloche.

Plant outdoors in April/May, (Weeks 14-21) once all danger of frost has passed.


Autumn sown:


Weeks 36-45:


Sow seed in trays or pots during for flowering the following year.

Leave the seed to germinate in a coldframe or unheated greenhouse over the winter months.

Plant outdoors in April/May, (Weeks 14-21) once all danger of frost has passed.


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