I’ve grown sweet peas for years now, and one of the first things I learned is that their height isn’t a one-size-fits-all situation. When I first started, I just assumed all sweet peas would shoot for the sky. What I found was, it really depends on the variety you pick and how much support you give them.
Most of the climbing sweet peas I’ve worked with tend to reach around 6 to 8 feet, sometimes even 10 feet if they’re really happy and have something sturdy to grab onto. But I’ve also tried some of the shorter, ‘knee-high’ mixes, and those stay much more compact, usually around a foot or two tall. It’s a good thing to check the seed packet before you plant, because a dwarf variety isn’t going to scale an arch trellis, and a climber will just flop over without proper support.
Picking the Right Sweet Pea for Your Space
When you’re thinking about sweet peas, it really boils down to what you want them to do in your garden. I’ve had success with different types in different spots.
Climbing Varieties for Vertical Impact
If you’re aiming for those dramatic, fragrant walls of blooms, you’ll want the climbing types. These are the ones that can easily hit 8-10 feet. I’ve grown Spencer Mix and some of the more traditional heirloom varieties, and they definitely need a robust structure. For a hot summer area like mine in Arizona, I’ve found that varieties like ‘Perfume Delight’ or ‘Jewels of Albion’ do a bit better, keeping their blooms longer into spring.
Bush and Dwarf Varieties for Containers and Small Gardens
For smaller spaces, or if you want sweet peas in a pot, the bush or dwarf varieties are the way to go. I once made the mistake of planting a climbing variety in a small container without much thought for support. It was a tangled mess. Now, if I’m using pots, I specifically look for varieties like ‘Knee-High Mix’ or ‘Explorer’. They’re still fragrant, but they don’t try to take over the whole patio. They’re also great for the front of a garden bed where you don’t want tall plants blocking the view.
Starting Sweet Peas the Right Way
Getting sweet peas off to a good start makes a big difference in how well they grow and how tall they ultimately get. I used to just direct sow everything, but I’ve learned a few tricks that really improve germination and plant vigor.
When to Sow for Success
Timing is crucial. Here in my mild winter area, I plant sweet pea seeds in the fall, usually from October through February. If you’re in a colder climate, you’ll want to start seeds indoors about 4-6 weeks before your last spring frost, or even earlier, like November to January, if you want blooms by late May. They really do prefer cool soil to get established, so planting them when the soil temperature is around 50-60°F (10-15°C) is ideal.
My Method for Sowing Seeds
I’ve heard a lot about soaking sweet pea seeds overnight, but honestly, I stopped doing that. I found too many of them would rot. Now, I sow them completely dry. The only exception is if I know I have a mouse problem, then I’ll soak them in liquid seaweed fertilizer. It seems to deter the mice and doesn’t harm the seed.
I always use root trainers for my sweet peas. They’re these long, thin cells with channels that direct the roots straight down. This prevents the roots from circling around the pot and encourages a really strong, deep root system. I put two seeds per cell, pressing them down about an inch and a half deep. They usually germinate in about 10 days.
Pinching for Bushier Growth
Once my seedlings have about three pairs of leaves – you’ll often see the first tendrils starting to form around this time – I pinch out the central growing tip. This might seem counterintuitive if you want them to grow tall, but it’s a game-changer. It forces the plant to send growth hormones back down into the roots and pushes out side shoots. The result is a much bushier, stronger plant with more flowers. I made this mistake for years, letting them grow as single stems, and they were always spindly.
Providing the Essential Support
This is where the ‘how tall’ question really gets answered. Without something to climb, even the most ambitious sweet pea variety won’t reach its potential. They’re natural climbers, and they need a structure to latch onto.
Choosing the Right Trellis
I’ve tried all sorts of supports. An arch trellis works beautifully if you have the space and want a really dramatic display. I’ve also used simple netting attached to wooden stakes, which is a budget-friendly option. Rebar trellises with bamboo poles wrapped in jute also work well. For sweet peas in a pot, an obelisk trellis is a fantastic choice; they happily wind their way up the sides.
The key is to set up the support before the plants get too big. Trying to wrangle established sweet pea vines onto a trellis is a tangled mess I wouldn’t wish on anyone. Their tendrils grab onto anything they can, and untangling them can damage the plant.
Training and Tying Up
Even with a trellis, sometimes the sweet pea vines need a little guidance. I usually gently tuck new growth into the trellis or tie them loosely with soft twine as they grow. This is especially important when they’re young and haven’t quite found their footing yet. I check them every few days once they start really vining to make sure they’re climbing in the right direction.
Ongoing Care for Healthy, Tall Plants
Sweet peas are what I’d call ‘heavy feeders.’ They need good soil and consistent care to keep producing those beautiful, fragrant blooms.
Soil and Nutrients
Before planting, I always amend my soil with plenty of compost. They love cool, moist, well-draining soil. Once flower buds start to appear, I begin feeding them with a high-potash fertilizer, something similar to what I use for my tomatoes. This really helps with flower production.
Watering and Mulching
Sweet peas need regular watering, especially when they’re establishing and during dry spells. I water deeply and consistently. Adding a layer of mulch around the base of the plants helps a lot with retaining soil moisture and keeping weeds down. This is particularly important for sweet peas in a pot, as containers tend to dry out faster.
Deadheading for Continuous Blooms
This is perhaps one of the most important things for getting a long season of flowers. You have to pick the blooms regularly. If you let sweet peas go to seed, the plant thinks its job is done and stops producing new flowers. I try to pick them every day or every other day once they start blooming. They don’t last super long in a vase – usually 3-5 days – and I learned the hard way that keeping them away from ripening fruit (like apples or bananas) is crucial, as the ethylene gas makes them wilt quickly.
My Takeaway on Sweet Pea Height
Ultimately, how tall your sweet peas grow is a combination of choosing the right variety, giving them a strong start, and providing consistent support and care. Don’t expect a dwarf variety to scale your pergola, and always give your climbers something sturdy to grab onto. With a little planning, you can have a magnificent display of these wonderfully fragrant flowers all season long.
