How to Grow AMAZING Sweet Peas in Containers

I started growing sweet peas in containers out of necessity. I had an incredible desire to experience in my own garden these gorgeous fragrant flowers I was seeing all over Instagram.  But I don’t own land. I’ve been renting for 10 years and have moved four times within that time period (once I had to move my baby sweet peas with me!) So container growing was, and still is, the only option for me. After five successful years growing sweet peas in containers I am ready to share my secrets!  I can tell you that they grow amazingly well and you will be astounded at the amount of blooms your plants will produce! 

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To get your sweet peas seeds started please visit my article HERE. Today’s post is all about what to do with your sweet pea seedlings after they have already been growing in their seedling pots and have developed a good root system (hopefully you planted them in autumn as I recommend in THIS POST). If you have been growing them indoors be sure to harden them off (get them used to sun and wind) slowly over the course of a week prior to planting them in their final homes. Note: sweet peas, Lathyrus odoratus, are NOT edible and are toxic if consumed.

Big Containers are Best

Choose your container wisely.  Buy as large a container as possible, and preferably made of plastic if you live in an arid climate like I do.  My containers are plastic, 20 inches wide by 16 inches deep, and hold 1.5 cubic feet of potting mix. This allows the plants to root deeply, provides some insulation from the heat, and makes it easier to maintain an even moisture level.  If you choose a smaller pot you will need to use fewer plants and be aware that the vines may get top heavy and topple on a windy day.  Stay away from terracotta pots if you live in a hot arid climate as they will dry out very quickly and your goal is to keep the roots as cool and moist as possible.  It is possible that if you live in an overly wet climate that terra cotta could work for you- please experiment or use what you know works in your environment!

Buy the Best Potting Mix

Do not use soil dug up from your garden.  It performs strangely in a pot and can compact and have other issues.  Use a high quality “potting mix”- the best you can afford.  I have always used FoxFarm Ocean Forest.  It is free draining and has plenty of nutrients.

Support the Vines

Your sweet pea vines need something sturdy to climb on.  I have found that the best and most attractive supports are 6 ft. bamboo canes.  They are inexpensive and last a long time. Sink six in a pot until you hit the bottom and wire or tie them together at the top forming a teepee shape.  Make sure the top is secure as you do not want the canes springing apart and ripping your vines. As the vines grow, tie them up the cane using garden ties.  I have always used a twist tie with cutter because it is easy and quick to cut a piece and twist it onto the cane and plant leaving a small amount of space between the two.  Once your plants really get growing, this will become a weekly “chore” (I find it quite relaxing).  Don’t neglect your vines and let them flop around in the wind.

Plant the Seedlings

In zone 8b I plant my seedlings into their big pot homes in February or March depending on the weather.  You don’t want to wait too long, but you also don’t want to plant them too early when temperatures are still dipping into the 20’s or teens.  They don’t mind frost, but if a brutally cold day happens it is much easier to move the seedling pots into the house or garage for protection than to move the large pots.

I plant my pots a bit on the heavy side because of lack of space, but they always do great regardless. Plant six seedling pots evenly spaced and in front of a bamboo cane in the large pots (which totals about 12 plants because there are usually actually 2 plants in each of my seedling pots).  I don’t recommend planting seeds directly into the big pots. If your climate is too wet the seeds could rot. Instead, start them off in quart sized pots in fall (warm climates) or late winter/early spring (cool climates) and then when they have established root systems move them into the big pots.  My paper towel/baggie method is a good way to sprout them if you have been struggling or have older seeds. 

Sweet Peas Need Sun

As long as the weather remains cool, sweet peas love being in full sun.  You will get the quickest growth and flowering if they are in full sun.  Once the heat begins to arrive (in late May and early June for me) the plants will last a bit longer if protected from the hot afternoon sun.  At the very least protect the roots by positioning them so the vines are in sun and the roots are in shade (some potted plants clustered around the sweet pea containers helps with this!) It also helps if you can protect the plants from the wind.

Water and Fertilize

Never let your sweet pea containers completely dry out.  Using large pots will make this easier. Conversely, you don’t want to overwater them either so always check your soil with your finger before watering.  Don’t water if the soil feels moist an inch or two below the surface.  Water if it feels dry.  I don’t use a lot of fertilizer because the potting soil I use has plenty.  I will sometimes provide a trowel or two of compost or a watering in of fish emulsion.  If the foliage looks pale definitely provide some fish emulsion.

Cut the Blooms and the Tendrils!

The more you harvest your sweet peas the more they will bloom for you.  Never let them go to seed as that sends a message to the plant to stop producing flowers.  It can almost become a chore keeping up with all of the flowers, but I think it is a great chore to have! You can pick them when all the flowers on a stem are open, or when the top flower buds are just starting to show color for longer vase life.  You will notice many tendrils on your vines as well. Since I tie my sweet peas to the bamboo canes, the tendrils serve no purpose and just make a mess wrapping themselves around neighboring vines and flowers and take energy from the plant.  I cut them off every time I harvest the flowers.  Make sure you do not cut the growing tip of the vine.

Pests and Diseases

As an update for 2023, birds have attacked my sweet pea seedlings! It remains to be seen if I will get any blooms this year because the damage was so extensive. If birds are a problem in your area I now recommend netting your seedlings after you plant them in the large pots until they have put on some considerable growth.

My plants are usually not bothered by pests and diseases until the hot weather arrives and begins to stress them out.  At that point I will often see powdery mildew and thrips appear on the older foliage.  Often this will coincide with bloom production slowing down- sweet peas really do not like the heat! If you want to try to control these issues you can try sticky traps and sprays, but in reality once temperatures are consistently in the high 90’s the sweet peas days are numbered and the vines will begin to die back and they will stop blooming.

I feel like I could go on and on about growing sweet peas in containers!  I hope that this post gives you a starting point for growing these gorgeous fragrant flowers.  As always, keep in mind that things may need to be tweaked to accommodate your individual climate and growing conditions.  I would love to read your comments and questions either down below or on my Instagram!

Happy Gardening,

Heather