Growing Annual Vines in Pots
Over the past three years I've been growing various annual vines in containers, trying about 6-8 different varieties of the most commonly found annual vines, each year. As you may have discovered yourself, annual vines like morning glories while beautiful and easy to germinate, can, and do, grow too quickly and with such vigor that they can, and will, get out of hand often before they bloom. Yet other annual vines are more tidy and manageable. I wanted to see what vines were the most manageable, and which ones were the most beautiful as a container plant, and which ones are best left to the trellis or telephone pole.
I remember reading in an old gardening book once that one should always approach vines with caution. They are biologically coded to be opportunistic, but that makes sense once you observe vines growing. They are simply designed to race up objects quickly to reach the canopy so that they can get sunlight and attract pollinators. I was reminded of this while botanizing in western China in 2018 when I saw clematis growing on a hillside in the Himalayas, often nearly completely covering the horizontal limbs of evergreens – looking more like a snowstorm had dusted each fir tree with a coating of snow. Clearly, clematis are designed to ramble through shrubs and trees more than they are designed to climb lamp posts.
I grew all of my annual vines in 14″ deep 12″ diameter clay pots (from a discount store at $9.99 each). These were perfect as I could set in 8 or so 3/8″ bamboo stakes that were 5′ long along the diameter (starting by spacing them like the hours on a clock, 3:00, 6:00, 9:00. etc, or like cutting a pizza into 8 pieces). I then would tie them at the top with twine to create a thin, teepee-type structure.
Knowing how your vine ‘climbs' is helpful, as sometimes you may need to add bird netting or chicken wire – even wrap the entire teepee with twin if the vine climbs by using tendrils (like grapes or sweet peas), while other vines naturally twine around the support, such as with morning glories. Then, there are vines with do neither, like nasturtiums – especially the yellow-flowers canary vine, which sometimes use their leaf stems to twine (the petioles) or they prefer to just tumble and creep over branches in the wild. These will require more help such as hand-tieing new growth with soft yarn or garden twine to get things going.
I tried to focus on the most common annual vines that any of us can find on a seed rack or in a seed catalog, but I also tried a few more focused trials – particularly with sweet peas, and other annual Lathyrus, just to see what they would look like if grown in pots. Out common cut flower sweet peas – Lathyrus odoratus, the Spencer varieties and the old fashioned cut flower sweet peas, which are not ideal for growing in pots, did do well if the pot was larger than the 12″ pots I first tried for the more rare, or unusual species. I will say that the species surprised me with how small many of them were once mature, and how unique the foliage and even the seed pods were – often even more interesting than their flowers were. The only downside was that they bloomed early, and only for a week or two, then set seed and died. Not a long-lived potted plant.
The cut flower types of sweet peas fared better in some 24″ clay pots and particularly the ones that I grew in an old 1940's metal cooler (with holes drilled in it). These grew taller, on an 8-foot-tall tomato cage, and did so well, that I may always grow some sweet peas this way.
An excellent choice for 12″ pots would be any of the Black Eyed Susan Vines, particularly the newer selections (like those found with registered, licensed names from brands like Proven Winners). All are fine, even the varieties you can start from seed indoors, under lights, but the better colors do seem to come from the newer selections. These not only grow quickly, but so aggressively that you will only need one per 12-14″ pot. One plant will send out dozens of shoots and quickly cover a 5-6 foot tall teepee. These tend to always look neat, though once they reach the top, you will need to retrain them down or prune them often. They can quickly take over any nearby teepees or shrubs if they touch them.
Morning glories, and their relatives may seem like a natural first choice, but proceed with caution as most will outgrow a pot before mid-summer, especially the species. I will say that the Japanese varieties (called Asagao in Japan) do make excellent potted plants (you know, the striped ones, and even many dwarfs and mutations available on eBay). There is an entire culture around growing these in Japan, where, like bonsai, they are grown in smaller pots and pruned heavily, often keeping teepees to only 14″ tall. I've grown many morning glories this way, and while the method even works with Heavenly Blue and other common varieties, it's labor intensive as you know how fast morning glories can grow. It's best done with the variegated-leaf Japanese varieties, however, but that merits another post.
There are some species of Morning glory however, which I did try. This year, I grew the wild species Ipomoea hederifolia var. lutea , a species that was completely new to me which was incredible, blooming all summer long, delighting the hummingbirds and forming a cloud of tiny, tubular yellow blooms that were about 1″ in diameter. The only problem was that the vine quickly outgrew my 14″ deep clay pot by mid-June, so I had to plant it out. Sliding the entire root ball and bamboo cane, which by July 4th were already completely covered with foliage and twining stems into my shrub border where it completely covered a Black Prince, eventually killing it by smothering it, but totally covering it with a cloud of yellow blooms that made the effect something that I want to repeat every year. There is a red species now that I want to try next year, which seems similar, I. coccinea.
The Spanish flag vine has always been a favorite of mine. I mean, cmon, ombre! It almost doesn't seem real, but it's a good candidate for pots as long as you know that it won't bloom until late summer, and it too can get a bit out of hand, though not as aggressive as let's say a regular blue morning glory might be, even though it's related. Once taxonomists listed it as Mina lobata, but it sits firmly in Convolvulaceae, the Morning glory family, and is properly known as Ipomoea lobata.
Some of my favorite annual vines remain the most common. Sky blue morning glories, like ‘Heavenly Blue', is pure nostalgia for me, as it reminds me of my dearest aunt (Aunt Ann) who lived in New Jersey, and grew it on her chainlink fence behind her home. It was a tiny, long garden in Trenton, but full of plants., such as was my grandfather's garden was nearby also in Trenton. That was where I first saw a passionflower vine growing, behind my grandfather's chicken coop. He was nearly 100 years old in the early 1980's and didn't speak much English, but he wanted to show me the passifloras when they were in bloom. I should mention that they too are good for large containers, but I didn't include them here as they aren't true annuals (even though we grow them that way up north).
I have to admit that the finest display came from the Purple Bell Vine, Rhodochiton atrosanguineus. IT used to be hard to find, but I find seedlings occasionally at some local Boston area nurseries. Like most vines, it's not going to be in bloom when you find it available as a seedling, and young plants can look rather weak and unpromising. All I can say is get it, if you find it, for few plants put on such a show. My towers were so attractive this past year that I set them around the garden as objects, even loaning a few to a client's garden photoshoot for a story in Architectural Digest. They are that attractive. You can grow them from seed, but it takes some patience.
Sow seeds in February, under lights and keep them warm. Transplant carefully into larger pots in spring, and eventually set the young plants into a big pot such as my 12 to 14″ long toms with 5′ bamboo canes. It's a twiner, which helps, but every bit of this plant looks lovely, from the burgundy-backed foliage to the amazing flowers that almost defy description. It starts blooming when young, so it just about always looks good. Best to start with new plants every year, though, as it is hard to winter over successfully in the north.
The Love in a Puff Vine (Cardiospermum halicacabum) is a true old-fashioned, if not heirloom plant that is fun to grow for its puffy, inflated seed pods that each contain a few of their distinctive seeds – each with a tiny beige heart them, hence, where it gets its name. Granted, it's not a vine for everyone, as it can look weedy or too casual for many. I love it, as I've seen it grown to great effect in urns set into the center of an herb garden at an estate in the Hudson Valley, and on a trellis in a friend's garden. You just have to be prepared for rampant growth, which is graceful, and know that one doesn't grow this plant for its inconspicuous tiny white blooms, but for the seed capsules, and the overall effect – a tangle of stems and foliage, which can look attractive in the right sort of setting.
Side by side, pots of vines displayed in a row can also be attractive. Each year I line a few walks and paths around the garden, or leading to the greenhouse with potted vines being trained onto bamboo teepees. It allows me to grow a number of vines in a small space, and I know that I can cut back any that get too unruly. In pots, the blooms are brought to eye level, but I have to say that more and more, I am attracted to the foliage than I am to the flowers.
Nasturtiums are naturally vines in the wilds of South America, but most have been bred to be shorter plants, yet a few remain – true heirlooms and worth playing with, to add something different to the garden. You may already know that I collect many of the tuberous Tropaeolum from the Andes, and grow them as winter-blooming vines in my greenhouse, but there are some very easy annual Tropaeolum, from the veining nasturtiums (like the one sees every spring at Boston's Isabella Stewart Gardner museum) or the overlooked Canary Vine, which you can still find in good seed catalogs.
Easy to grow, the Canary Vine (also sold as Canary Creeper, or the Canary Bird Vine) has large seeds like the nasturtiums you already love, but it is an aggressive grower, and probably not my best choice for a container unless you have a bigger one – let's say 24 -30″ wide. It dislikes drying out in summer, which can kill a vine in just a day (believe me, I know) and the foliage can yellow practically overnight if you let it dry out. The vine can be very effective if grown in a large pot as long as you have something for it to climb on. I'd say that it's better if planted into the ground, though. It's not a twiner, no tendrils either, so it's best climbing through twigs or over a shrub. I once planted a big parrot cage that we had left out on the deck (when our Parrot Kojo flew away). We hoped she would return, but a canary vine took off in a large pot, so I set it inside the parrot cage (seemed ironic at the time). It completely covered the cage which was about 4′ x 6′ on rollers, and became quite the spectacle.
Another morning glory relative which is slightly better behaved is the Cypress vine, or Cardinal Vine. Closely aligned with Ipomoea x multifida, and related to the red flowers I. coccinea, this annual vine will quickly cover a tower in a few months from a sowing in late May. I sow all of my Ipomoea species and selections near the end of May, as they are rapid growers, and really don't need a head start. Do know that in the south, and in warmer zones many of these morning glory relatives can be considered to be invasive, as they self-seed and can spread, so check your local restrictions before planting.
Vines in pots will be like trying to raise three teenage brothers. They will fight with each other, and try to dominate each other constantly getting into trouble. Try your best to raise them independently but sternly, training them almost every day (as they'll forget) and then enjoy the results of your labor once they reach maturity and bloom. It's may seem like all is lost, but be firm, and don't be afraid to control them a bit.
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