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I’ve just held a party on the main lawn in my garden. Over the last couple of months, in preparation for the event, I’ve been working away at planting, weeding and mulching this area. Well there is more I would have liked to have done, but the garden did provide a beautiful backdrop to celebrations and drew lots of favourable comments.
Ipomaea cultivars form a blanket of colour that glows in the afternoon sun
This is an area where I am focussing on hot colours – brilliant reds, oranges and yellows. The plants that drew the most attention from guests were the carpets of ornamental sweet potatoes. Their leaves were simply radiant. They really love the warmth, moisture and humidity we have been having and at this time of the year the leaves are larger, softer and more richly coloured than during the drier winter months. [Click on the photos for larger versions]
The simple green leafed and edible sweet potato (Ipomoea batatas) can make a great ground cover. I remember many years ago visiting clients on the Gold Coast who had progressively planted cuttings of the plant down a steep slope. Not only did it stabilise the area and prevent weed incursion, but it also provided a very attractive lush green backdrop. The plants could be progressively removed for future replanting – and it cost virtually nothing – in fact it provided free food.
Finding tubers on this scale can be tricky, in fact it can be tricky finding them in the vegie garden, however sweet potatoes furnish fantastic and nutritious ‘greens’. Younger leaves can be used in casseroles, stews, stir fries and curries. The youngest leaves and leaf buds are great in salads and add colour and textural variety. But try the leaves of the plant first. Some cultivars have sweet and tender leaves, whilst others are a little coarse and have a slightly strange flavour.
Ornamental sweet potatoes were first introduced to Australia in the early 1990s. While these cultivars continue to be popular overseas, they failed to attract much attention in this country and are no longer grown commercially. However they are worth looking out for. They include:
Sweet potato Ipomaea batatas ‘Margarita’ has chartreuse to butter yellow leaves
‘Margarita’ (‘Marguerite’)
A favourite of mine with its large, brilliant chartreuse to butter yellow leaves (depending on the time of year), this plant is particularly robust and will cover a large area fairly readily. The plant was released by the Department of Horticulture New Crops Program at the University of Georgia in 1996 and was discovered in the Garden of a Mr Hunter Stubbs of Raleigh, North Carolina. Introduced into Australia soon after, it is probably most well known as the groundcover in the central Cairns traffic islands, thanks to inspired planting by landscape architect Anton Van der Schans. I suspect most plants originate from this source as I have never seen it for sale in a Queensland nursery, although it is now widely grown by keen gardeners.
‘Blackie’
This is a very vigorous blackish-purple leafed cultivar that was grown in North Queensland during the late 1990s. It is still very popular plant overseas. It has maple-like leaves and is a vigorous trailing cultivar.
‘Tricolor’ (‘Pink Frost’)
A stunning plant, it has grey-green leaves edged in pink. Popular overseas, I understand the plant is a little tender and may need a little protection over the cooler months.
I have been unable to track down these last two cultivars in recent years and would love to use them in my garden. I suspect they are still grown in north Queensland. If any reader grows them or knows a source, please contact me.
Sweet potato Ipomaea batatas ‘Sweet Caroline Sweetheart Red’ is my favourite, with its lime new growth, just like a patchwork of autumn leaves
The recent interest in ornamental sweet potato plants has been due to the release of a number of new cultivars originating from breeding carried out at North Carolina State University. This programme focused on producing colourful compact plants. Cultivars Margarita and Blackie featured in some of the parentage. The Sweet Caroline Sweetheart series was first released in Australia in 2008.
As with many new plant introductions, there was very little information available regarding these plants and I fear that by the time the public cotton on to them, the plants will no longer be commercially available – a frequent occurrence in this country. Three cultivars were originally released:
Sweet potato Ipomaea batatas ‘Sweetheart Purple’ is the tallest growing and trailing of the cultivars
‘Sweet Caroline Sweetheart Red’ (PBR)
My personal favourite. It has reddish-brown leaves and yellowish green new growth. The effect is a kaleidoscope of these colours and reminds me of a patchwork of fallen autumn leaves
‘Sweet Caroline Sweetheart Purple’ (PBR)
This plant has elongated purplish- black leaves which become very large during a warm, wet summer. It is the tallest growing and trailing of the cultivars.
Sweet potato Ipomaea batatas ‘Sweetheart Light Green’ forms a dense cover
‘Sweet Caroline Sweetheart Light Green’ (PBR)
Carrying pale, yellowish green heart shaped leaves, this cultivar is very dense and compact.
This year several new cultivars were released in Australia:
‘Sweet Caroline Purple’
The liquidamber shaped leaves and the stems are a purplish- black. The plant trails along the ground.
‘Sweet Caroline Bronze’
Probably the most rambling of these plants, the leaves are maple-like and a pale brown colour.
Sweet potato Ipomaea batatas ‘Sweetheart Bronze’ is the most rambling
‘Sweet Caroline light Green’
A compact plant that forms a very dense cover. It has yellowish green maple-like leaves.
Sweet potatoes can be readily propagated by cuttings. During the summer months these can be simply planted insitu and they will establish rapidly. Note that The Sweet Caroline Sweetheart series is currently covered by the Australian Plant Breeder’s Rights (PBR) which provides the grower with exclusive rights to sell, produce, distribute and receive royalties from sales. This does however allow the purchaser to propagate the plant for their own use and these plants do look great mass planted as swards of colour in the landscape.
I find sweet potato plants are generally low maintenance, although they may require a bit of trimming over the summer months to keep them contained. They are virtually pest free. However there is one pest which can annihilate a bed – the bush turkey. They seem to discover a tuber and then progressively destroy the patch scraping plants away to find more. I always have a couple of patches of each cultivar, for the problem only seems to be bad in spring when the males need added sustenance to build their mounds. These are persistent creatures and once a turkey starts, there is little you can do to persuade it to go elsewhere.
Occasionally I get tiny holes in the leaves of some cultivars, but this seems to be short-term in nature and I suspect some predator insect moves in as these symptoms soon disappear.
Plants can be used in a variety of ways. In subtropical and tropical areas the plants are evergreen groundcovers and grow all year round being particularly vigorous over the warmer, wetter, summer months. In fact I need to prune them back this time of year or they will cover the lawn or nearby plantings. This can have an advantage where you want temporary cover – and plants can be readily composted.
Plants look great in large pots or hanging baskets with their distinctive trailing growth. Along with summer bedding, this is how they are generally grown in cooler climates, being treated as annuals.
Ipomaea ‘Sweet Caroline Sweetheart Red’ with Pennisetum advena ‘Dwarf’
Plants also complement various garden styles. The bold, brilliantly coloured leaves can be used to complement cordylines, heliconias, palms in a tropical inspired garden. They add colour and look spectacular in a potager or ornamental vegetable garden and are handy for incorporating in various dishes.
Consider plant partnerships. I have ‘Margartia’ next to Tradescantia pallida ’Purpurea’ and the contrasting, complementary colours simply sing to one another.
Some councils have strange views of this plant. I once helped Brisbane City Council write a brochure on hardy vegetables. Sweet potato was removed by the environmental section as they regarded all Ipomoea species as being potential weed species. As the sweet potato has been grown in the region for over 150 years, I suspect we would know its weed potential by now. It appears to be nil. I suspect the bush turkeys and bandicoots soon finish it off.
The BIG question I keep getting asked is do ornamental sweet potatoes produce edible tubers? Well yes they do….. but the tubers usually aren’t as large or regular as the ones we generally eat. They can be small, contorted and difficult to clean or peel. Look upon them as an additional bonus and dig them up just before you plan to use them so they are sweet and simply require a quick wash and trim…..and don’t forget the young leaves as they can provide a colourful garnish to a salad.
Want more foliage colour in the landscape? These could be the plants for you. What’s more they are lush and dense groundcovers that provide weed-free cover to garden beds and banks.
Hi Arno
I live in Cairns and planted the purple and the lime green varieties as a groundcover on a bank. But they are continually eaten by little green grasshoppers. After 12 months of this – I did think I would have a breather during winter – I have given up and now are trying alternatives. I do love the look of them when they are healthy though.
Barb
Hello Barb
I have had issues with grasshoppers, but have found that I can minimise their impact with good plant nutrition. I apply garden lime and silica (diatomaceous earth) to ensure the plants have well developed leaf structure. I also use balanced biological fertilisers containing ground rock minerals. I consider that many insect problems relate to poor nutrition and that this is a big problem in the tropics and subtropics due to the heavy, leaching rain.
I also keep an eye on soil pH and try to keep it between 6.5 and 7 (depending on plantings). I focus on retaining carbon/organic matter in the soil,mulching and adding humates to ensure the retention of nutrients and stimulating biological activity to enhance plant uptake.
Since focussing more on nutrition I have not had such a problem with grasshoppers. I am told that the silica in the plant leaves wears down the grasshoppers jaws and that plants with adequate nutrition have slightly alcoholic rather than sugary sap – a big turnoff.
It may be worth having another go!
Arno
What is the large leafed plant you have in the top picture? Is it drought tolerant and how much sun does it need?
Hello Margaret
the plant in the top photo is Agave attenuata or soft leaved Agave. It is a tough and drough hardy plant that thrives in well drained soils in the tropics, subtropics and warm temperate areas. The plant grows well in full sun or semi-shaded locations. It is generally available from nurseries.
I would love to know where I can pick up some cuttings of the Ornamental Sweet Potato in the purple and lime green. Any help would be appreciated. Thank you.
Hello Hazel
Many of the plants I have discussed are currently covered by Plant Breeder’s Rights (PBR) in Australia and hence are best purchased from your local Garden Centre. The popular clone ‘Margarita’ does not have a PBR and is often available through local garden clubs.
I hope you have lots of fun growing these plants.
Arno
Hi,
I am looking for the contact details of Mr. Anton Van der Schans…could you help?
Regards,
Anjali
I would really love to know where to pick some off these up? I wish they were commercially available.
Hello Jasmine
these plants are commercially available in most areas and I have seen them in Garden Centres throughout Queensland, New South Wales over the last few months. In fact the range of cultivars is increasing. Like most plants, they are generally available seasonally and in this case, during the warmer months of the year. If you can’t find them, ask your local Garden Centre to order some in.
Arno
Hi Arno, I bought the Sweet Caroline Sweetheart Purple’ last summer and it looked stunning. However, during the autumn I started to notice holes in the leave (something eating it) I sprayed pest oil. Now one plant is completely decimated (no leaves on vine) and my others are heading that way. Can you suggest anything (I have a pet dog) so am concerned about what to use. Thank you
Hello Vickie
Yes, sweet potatoes leaves can be attractive to a wide variety of herbivores. In my garden, my worst offenders are wallabies, deer and bush turkeys which move into my garden during the drier winter months. However the holes you describe suggest damage by chewing insects. With decimation going from holes to whole leaves, I would imagine the culprit could be caterpillars and in particular Hawk Moth Larvae which love these leaves.
In my own garden, I find that sweet potato leaves are fairly resistant to insect pest damage if their cultural needs are met – in particular soil moisture and nutrition. I find damage occurring when plants dry out too much or if they are deficient in key minerals and in particular trace elements. I’m not sure where you live, however it it is south of Central New South Wales, temperatures may be stressing your plants slightly and hence they may be more attractive to these herbivores.
My suggestions are to wait until the weather starts to warm in spring and then resume a feeding program. I would do a pH check ( your local Garden Centre will do this for free) and add garden lime if your pH is below 7 (acid). Sweet potatoes enjoy good levels of Calcium as do many of the beneficial fungi that live in our soils and on which plants have symbiotic relationships. Couple this with a balanced biological or organic fertiliser which contains all necessary plant nutrients including essential trace elements.
In regards to pesticides, I like to use these as a last resort as they can often have a negative impact on beneficial animals and can drip down into the soil and affect the beneficial soil organisms. White oil relies on coating and suffocating the existing insects and is effective on more sedentary sucking insects, however the more mobile chewing insects (which are doing the damage to your plants) may be retiring down to the soil and out of range during the day or when you are spraying.
Good luck with your plants. If you can boost their health and vigour during the next growing season, you may avoid this happening again next winter. Of all the ornamental sweet potatoes, ‘Sweet Caroline Sweetheart Purple’ is probably the hardiest and most pest resistant.
Arno
Thanks for the info. All five of my plants have now died off. I live in SA and we’ve had an unusually extra cold winter, so not sure if they didn’t tolerate the weather we’ve had. (I had two out the front that weren’t being eaten like the others out the back) but they too died off all about the same time. However, I’m obsessed with these plants so i’m going to try again this spring. When pulling up the dead plants one came up with a bulb (i’m assuming I can try replant this?)
HI Vickie – I wouldn’t be too fast to dig them up. Mine in Sydney die back to their underground tubers during the winter but pop up again in late spring.
Where abouts in sa r u vickie? I am desperately trying to get some of this but am struggling to find it
Hello Arno,
I had two of these in 300mm pots, they were flourishing until somehow the local scrub turkey worked out that the fleshy succulent roots would be tasty. Both pots were tipped over and the roots eaten. I replanted the rootless ‘cuttings’ and the turkey allowed just enough time for roots to re-develop before upending the pots agian. I have given up for now.
Hello Darryl
Scrub Turkeys love sweet potatoes and will soon destroy established plants in the garden. I have also had this problem so I am planning to grow them under pegged chicken wire this year, as I have seen other people have success growing them this way. Plants can also be grown in hanging baskets and elevated pots, so don’t give up.
Arno
Arno,
Sweet potatoe leaves are commonly eater by Asian
I planted the same purple variety at my garden but no one is certain if the leaves of this plant/sweet potato is edible.
I read somewhe that plants with natural coloring have more health benefits.
Would like to try eating the purple leaves if they are safe or not poisonous?
Are there any study if the purple leaves are poisonous?
Thanks
Hello Sing
Various references note how the leaves of sweet potatoes appear are widely eaten around the world. I have eaten the leaves of a number of purple leaved cultivars, as have friends.
One thing to note is that the leaves vary in flavour. Some are quite sweet and delicious, others are bitter or have an unpleasant flavour. Some leaves are soft and delicate others are coarse and stringy. A number of cultivars are grown for their delicious leaves rather than their roots and at least 2 of these leaf cultivars are grown in Australia.
There are at least 4 purplish cultivars locally available. I found some have tough and unpleasantly flavoured leaves and I don’t find them palatable. I can’t remember which one I liked the most, but I think it was ‘Sweet Caroline Sweetheart Red’.
Arno
I love these plants and use them in my Perth garden. They are fab for most of the year but look rather straggly in the cooler months. Unless something changes Perth gardeners will only find them for sale in December to February when they look lush and fabulous. I also use them as inside decoration in float bowls where they quickly strike roots and last for a couple of weeks in a vase
Hello Deryn
plants seem to be only available here in summer as well.
They certainly look their best over the warmer months, and don’t grow as strongly or look as vivid over the winter months.
I have a sweet potato vine with large wrinkly seed pods growin on the vine
Somewhere I read they’re edible but there is no way I would consider
that as being part of the deadly night shade family and when cut open
Yes lots of seeds with a scary white milk that say to me DON’T eat
So question ….are some edible and others dangerous ?
Cheers Jennifer
Hi Jennifer – sweet potato is not part of the deadly nightshade family as it is not a true potato. It’s in the Convolvulaceae family, with morning glory. You can certainly eat sweet potato leaves and many people think they are delicious.
Re the milky sap, if you look closely when you cut a sweet potato, you will see beads of white milky liquid form on the cut surface too. However as I can’t find any verified information about whether sweet potato seeds and seed pods are safe to eat, I would err on the side of caution and not eat them. Although I’m not quite sure why you would want to eat a shrivelled seed pod anyway?
Excellent article Arno. Great reading and listening. I grow the green and a purple variety, which is rampant in one of my garden beds. I was looking for a little more info today and discovered your site. I’m transplanting them to another area for winter, with a little more shade and water. Thanks so much.
Hello Dean
Glad to hear that you enjoyed my article. You will enjoy growing some of the other ornamental cultivars as well. I hope your plants do well over the winter months.
Arno