How to grow autumn sown sweet peas

Why should I grow autumn sown sweet peas?

Hardy annuals, like sweet peas, will grow, flower and die in one year. By sowing in the Autumn instead of the Spring you give the plant 6 months of extra growth. By next summer they are able to sustain bigger, earlier flowers on strong stems.

You also have two seasons to sow (Autumn and Spring) to guarantee success and a longer flowering period. Flowering dates vary from year to year so a succession of sweet peas is particularly important if you plan to have your own beautiful scented flowers for a wedding or family celebration.

Is it more complicated than sowing in the Spring?

Yes and No.

Yes, you will have to care for your plants over winter.

No, you will have virtually indestructible plants by the time they go out into the  soil.

Ok, so you have sort of convinced me, how do I go about it?

You will need the following:

Deep pots such as rootrainers or long tom pots and some multi-purpose compost with a slow release fertiliser added (that’s included in almost all commercial composts).

A place to put your sweet peas where they will get plenty of cold but won’t be as exposed as if they were in the open garden. A porch, cold frame or unheated greenhouse is ideal.

Anything else?

Seeds obviously (which you can buy from our online shop). The other thing to consider is mice. They LOVE sweet peas when they are seeds or very small seedlings. Protect your pots so mice can’t get access to the seed. That could be anything from a platform with legs that are tucked underneath so the mice can’t make it past the overhang or a clear lid to cover your sweet peas (Rootrainers supply these with the pots)

Keep an eye out for slugs too by checking the base of your pots (where they love to lurk) and removing them.

When should I sow my seeds?

You can sow anytime from early October to mid November when the days allow for a long gentle germination. Push them gently into the damp but not wet compost until they are covered by about 2cms of soil.

How do I know if I am getting it right?

What you are aiming for is lots of roots and the minimum of top growth. If you see green shoots emerging slowly and gradually putting on leaves over a period of about 3 weeks you have got it right. If your plants are turning into a jungle of green you have got them too warm and they need to go somewhere cooler to slow their growth for a bit.

But how cold is too cold?

Sweet peas can withstand temperatures of about -5 at night but will not like to be frozen in their pots all day. If you overdo it and lose the top growth, chances are, if you give them some warmth they will have established enough root to sprout again.

I’ve completely overdone it and my sweet peas look like triffids, what should I do?

Pinch out the main stem back to 2 sets of leaves with your finger and thumb to reduce the top growth and send your plants to the sin bin as detailed above. If you have had them on a windowsill or similar, be careful not to abandon them to the cold too fast. They will need hardening off. Put them outside in the day time and bring in at night for a week before leaving them out full time.

It’s Spring! My plants are busting to go out, when should I put them in the ground?

This depends a lot on where you live but once the worst frosts are over is a good time. For us in Lincolnshire this is from Mid-March onwards. A good test is to put your hand on the ground every few days and you will gradually start to feel the soil is no longer arctic. Keep an eye out for weed seedlings appearing, this is a good indicator that your plants will also put on growth in the ground.

I still have more questions, can you help?

If you need help with individual problems you can send us an email.

I meant to Autumn Sow Sweet Peas but it’s too late….

Don’t worry, you can buy them from our garden shop where we have done all the hard work and they are ready to go out to produce strong plants with early flowers.