Day 4 of the Advent Calendar: Sweet Pea 'Mammoth Mix'

Sweet Peas have it all; they smell divine, look incredible climbing up trellis or supports in your garden, and are an absolute 'must-have' for your garden. They are easy to grow from seed and create a stunning display throughout the summer. They flower prolifically, so you can cut bunches of them and gather them into posies to give to friends and family- bringing so much joy!

I chose the Sweet Pea 'Mammoth Mix' for the advent calendar because it came highly recommended by one of the best Sweet Pea growers in the country. A highly scented, colourful mix with plenty of long stems, sturdy growth and reliable germination. I couldn't say no! I loved the colourful mix and thought how special it will be later in the year to cut bunches and bunches of flowers. I hope you love the Sweet Peas in Day 4 and enjoy growing them.


You can sow Sweet Peas from Autumn onwards, all the way until Spring. Autumn sown Sweet Peas get a head start in establishing roots over the winter months before then growing up the supports or trellis when the warmer weather happens. If you sow in Spring, you will still have beautiful blooms but they will take a bit longer to flower so patience is needed, and they might not be quite as tall as the autumn sown Sweet Peas. (But they still put on a wonderful show so don’t be put off if it’s your first year growing and planting this Spring).


It is pretty simple to sow Sweet Peas- nothing fancy needed! Grab some pots. I use 9cm pots, but you can buy root trainers. You could also use loo roll tubes, make your own newspaper pots, or re-use some plastic- old milk cartons could work (just please remember to drill holes in the bottom for drainage!). Once you’ve got your pots you will need some multi-purpose compost (even better if you choose peat-free as it is better for the environment).  No need to mix anything into the compost, simply fill up the pots right to the top.

I place three seeds in each pot. Place them on top of the soil and then push them into the compost about 3cm deep (roughly knuckle deep!). and Remember it doesn’t have to be exact or precise- that’s the beauty with Sweet Peas!

Then ensure you label the pot with what the variety is eg ‘Sweet Pea Charlie’s Angel. Top tip is to label each pot, as otherwise when you go to plant them out or move them in Spring they get all mixed up (learnt from experience on this one!).

Give the pot a water so the compost is moist and then place the pot on a warm sunny windowsill, or in a greenhouse. If you have a cold frame I would recommend placing the pot inside until you see green shoots coming out of the soil and then you could move out to the cold frame if you need more space. If often get asked how often to water the Sweet Peas- this is really hard to answer as it all depends on how warm and sunny the position you chose is. I would certainly check on them every 3 days and ensure the compost is moist to touch. Over watering won’t help establish strong plants so try not to over-do it, and certainly don’t let them sit in water for long periods as this will rot the seed and roots.

You should then start to see green shoots within a couple of weeks. You don’t need to do anything different until they have two sets of leaves on the plant- just keep watering and checking on them. If you’re running out of windowsill space and have a cold frame then now might be good to move them, but ensure they are protected- the seeds won’t germinate outside on their own and the small seedlings may get frost damage if left out.


When the plants are 10cm tall, then pinch out the tips to encourage bushy growth. You can use scissors or small secateurs, but I simply use my thumb and forefinger to pinch them out. By taking out the top leaves you encourage the cells below to send out a branch- this is good because the extra branch means you will have another upwards growing branch of flowers. It might seem scary when you first do it- but trust me- it is so worth it when you get a shed load more flowers! Be brave!

After this you simply need to ensure they don’t dry out by keeping them watered. Don’t worry if they get tall and start flopping a bit, you can put a small stick into each pot to help keep them upright if you have a lot of Sweet Peas growing and don’t want them to get tangled, but don’t worry as soon as you plant them out they will soon grow upright. Most varieties have tendrils that will ‘self-cling’ to supports, but some sweet peas will need tying in.

'Harden off' your Sweet Peas by placing them outside during the day and then bring them inside or under cover at night. Do this for 2 weeks and this will hugely benefit the plants. It's not only to help with the temperature, but also it helps the plants get stronger to things like wind and also their leaves adapt to ensure they don't lose moisture so fast in the heat. Remember if you are leaving them outside during the day that the wind can dry the pots out so you may need to water them slightly more. Once you've spent 2 weeks doing the hokey cokey and bringing them in and out, then you are ready to plant them in their final position.


Create a structure for the Sweet Peas to grow up:

Plant sweet peas in an open, sunny position in a well-drained but moisture-retentive soil. If you’re short on space then remember Sweet peas are well suited to growing in pots- planted in a large pot on a patio adds lovely scent! Sweet Peas are hungry plants so ensure you have plenty of organic matter and nutrients dug into the soil before you plant. (A bag of well-rotted manure from a garden centre would help a lot!) Then when they’re planted and you see your first flower then feed weekly with a high potash fertisliser (I use tomato food!). This helps to give the plant all the nutrients it needs to grow strong and produce plenty of blooms. I wasn’t sold on the need for feeding plants, but the year I did feed them was revolutionary! The lovely Amy at @chicksandveg does a #Fridayfeed which always reminds me to do it each week throughout summer.  

Keep ‘tying in’ your Sweet Peas. This simply means tying them into the support so they grow where you want them and they’re less likely to sprawl over all your borders and look messy. Use biodegradable twine as when the Sweet Peas have finished you can compost all of it together. (You’ll thank yourself in Autumn!)

Water regularly, especially in hot weather!

Every week I go through all the plants and pick all the flowers in bloom, this encourages more flowers. As the season goes on it can be hard to keep on top of so many blooms and you may miss a few, that’s ok, if you see a seed pod forming then cut this off the plan as you don’t want the energy going to forming seeds just yet.

You’ll notice that as the season goes on you will get shorter stemmed blooms, particularly nearer the top of the Sweet Pea plant- this is totally normal!

I hope this has given you some tips and guidance on how to grow your Sweet Peas. If you have any questions or tips you think everyone should know about then do comment below.


Happy growing!

Lizzie xx




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