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Why are my sweet peas turning brown?

A wonderful sweet pea display really is a sight to behold, but if your sweet pea plants are looking decidedly more brown than beautiful then it is time to do something about it. Here we will look at some of the more common reasons why your sweet peas may be turning brown and what you can do about it.

If you have a lot of strong growth and it is only the older leaves at the bottom of the plant that is turning yellowy-brown then this is to be expected and is normal on sweet peas, simply remove these leaves and allow the plants to grow as normal.

If the problem is more serious than this then read on for more reasons as to why your sweet peas may be turning brown.

Mixed colours of sweet pea flowers
Mixed colours of sweet pea flowers

Why can sweet pea leaves turn brown?

There are a few different reasons why the leaves on a sweet pea may turn brown, some common and some not so common. I will start with the more common causes as this is what will likely be causing your problems.

Root Damage

The most common reason for leaves turning brown on sweet peas is that you have damaged the roots. Like all pea plants, sweet peas have really sensitive roots and don’t like them being moved or damaged at all.

If you have just replanted your sweet peas either from a seed tray or small pot into the ground or a larger pot then this may well be the cause of your problems. As gentle and as careful as you may have been you will still have disturbed the roots of the plants and sweet peas really don’t like this.

The good news is that this problem resolves itself quite simply with time, just allow the plant time to repair and regrow any damaged roots and it will soon be looking better.


If sweet peas are sat in very damp soil all of the time then they can suffer from a problem called root rot. This is just as the name would suggest, the roots begin to rot from all the moisture.

Sweet peas do like fairly moist soil so to have this issue they have to be really overwatered. This can happen in pots that don’t have proper draining and leave the roots of the plant sitting in water.

Root rot causes the same issues as damaging the roots by transplanting and the solution is the same. The plant just needs time to recover and obviously less water. This is obviously easier to control if they are in a pot, if your sweet peas are in the ground then it may be a job for the following season to improve the drainage in that area.

Infections / Viruses

Brown leaves in any plant can be a sign of illness in the plant caused by an infection or virus. With a short-lived annuals like sweet peas, there is really not much you can do about this and it really isn’t worth the effort to try and save the plant.

If it is looking fairly bad then you may want to remove the sweet peas from the garden to remove the risk of the illness spreading. Whatever you do, don’t put the dead sweet peas on your compost heap as you may risk spreading whatever was affecting them all over your garden.


sweet peas, (Lathyrus odoratus) are a flowering plant belonging to the legume family. They are an annual flower that loves to climb and spread, in the right conditions and with the correct support they can grow to 2 and a half meters tall!

Unlike many other legumes which are grown to be eaten, sweet peas are grown for purely aesthetic reasons. There is evidence to suggest that the pea seeds from a sweet pea plant are actually toxic to humans and not fit for consumption even if this was desired.

Sweetpea FAQ’s

Are sweet peas perennial?

No sweet peas are an annual plant, they will not come back year after year.

Can you eat sweetpeas?

No, sweet peas are grown purely for their looks. Unlike many other legumes, they are actually toxic to humans if consumed.

Are sweet peas poisonous to pets?

Yes, as they are poisonous to humans they are also poisonous to pets, so make sure you keep an eye on your pets when they are hovering around sweet peas.

How high can sweet peas grow?

With the proper support, sweet peas can grow to 2m or even slightly above!

When do you grow sweet peas?

The traditional season for sweet peas is June and July but with the right care and attention, they can be both started earlier and grown later into the season. Regular deadheading of sweetpeas can massively prolong their flowering period.

How to germinate sweet peas?

I like to soak my sweet pea seeds in water for 24 hours before planting them in a seed tray. This soaking helps to break down the tough shell around the seed allowing them to germinate better.