The leaves are turning yellow and falling off at the bottom. The top of the vine seems healthy. Is there anything that can be done to save the sweet pea plants?
Hello, and thank you for contacting the Toronto Master Gardeners.
First, I’m wondering if your peas are sweet peas (Lathyrus odoratus), the ornamental climbing flowering vine, or a green pea such as a sugar snap pea (Pisum sativum or Lathyrus oleraceus, depending on who you talk to; a name change has been proposed). It is a bit hard to tell from your photo!
In general however, peas are a cool-weather thriving annual that prefer evenly moist soils. Sweet peas have deep root systems and are heavy feeders. Because they are in a pot and it’s hard to tell how deep it is, it’s possible their root systems do not have enough space to grow, and that this is making it challenging for them to take up enough nutrients. It also appears your sweet peas may have been started earlier indoors or at a nursery, given their size and that they already have formed seed pods. I have some in my own garden that I planted directly into the soil in early May, and they are only about 10 cm tall, with no flower buds yet (although I probably started mine a little late).
This previous Toronto Master Gardener’s answer goes into detail about growing sweet peas and recommends mulching to help ensure the soil stays evenly moist, and to provide a liquid fertilizer every two weeks, or add compost to the top layer of the soil. If your container is shallow, consider repotting the sweet pea into a deeper container to provide ample space for root development for the entire growing season.
The Peterborough Master Gardener’s recommend deadheading your sweet peas as flowers are spent to prevent setting seed, as once they do, they will cease flowering.
Finally, many experts recommend pinching out the growing tips after they have grown about 5 cm to encourage branching, and to protect the plants from afternoon sun, especially as the hotter weather sets in.
For more insights into growing sweet peas:
Planting wonderful sweet peas, University of Missouri Extension
Sweet peas, Cornell College of Agriculture and Life Sciences