Sweet potatoes are a subtropical crop that grows very well in Melbourne. I’ve grown them for years now and have had some fantastic results. I’ve even grown sweet potatoes in Kyneton which has a cool-temperate climate and a much shorter growing season. Here’s what I’ve learnt about growing sweet potatoes.
Propagation of sweet potatoes
The easiest way to grow sweet potatoes is by taking cuttings from an existing vine. This can be done at any time the plant is strong and healthy. In Melbourne, it is usually done in May when the previous crop is lifted. The cuttings can be placed in a jar of water to take root. I’ve also had success with immediately potting cuttings up in potting mix.
In Melbourne, you’ll need to protect young plants from cool weather. Cuttings will need to be protected in a greenhouse, or by growing on a windowsill during the winter.
If you don’t have access to an existing plant from which to take cuttings, you’ll need to grow some sweet potato “slips”. To do this suspend a sweet potato the tuber over a glass of water (toothpicks may assist with this). Half of the tuber should be submerged and half out of the water.
Place the glass in a warm position, such as on a window sill. After a few weeks the tuber will sprout many new shoots. I’ve actually had better success by planting the sweet potato tuber in potting mix. with half the tuber buried and half sticking out of the top.
Once the shoots have formed roots at their base, you remove them by twisting, trying to retain as many of the roots as possible. Place the shoots into a shallow dish of water until they establish a stronger root system and then pot up, or transplant out.
Some nurseries also sell sweet potato plants in spring and summer.
Location and planting of sweet potatoes
Sweet potatoes are a subtropical plant. They need full sun to enable good yields in Melbourne gardens. Limiting their access to sunlight may limit the size of the tubers developed by the plant. Growing them in a warm microclimate will give best results. Dig plenty of compost and organic matter into the soil. Plant the young plants about a metre apart. I’ve had best results by planting young plants into the garden in mid-late November. Be prepared for them to take over a space of several square metres of garden per plant.
I haven’t tried, but you can train sweet potatoes up a trellis (more on trellis options here). However, it apparently reduces the size of the tuber that develops. I have grown sweet potatoes in a “Three Sisters” companion planting garden. The sweet potatoes were a less rampant option to grow in place of pumpkin (squash in the original three-sisters). I found that once harvested, the sweet corn plants died back and enabled the light to penetrate down to the sweet potatoes. This ensured good yields from the sweet potato vines.
Sweet potatoes need regular watering and warm weather to thrive and yield well. Read more about vegetable patch watering and irrigation.
Cant wait to harvest your tubers?
I really enjoy growing sweet potatoes. However, the yield isn’t always that great considering the space the vines take up. Fortunately, you can also eat the leaves, either steamed or in salads. Sweet potato leaves are known as camote tops (or kamote tops) in Spanish-speaking countries.
The leaves are most tender in late summer. Late summer is a time that can be challenging to grow other leafy greens, such as lettuce and spinach. The heat and long days often make young lettuces bolt. So sweet potato leaves can add variety to your summer salads.
Harvesting your sweet potatoes
The tender vines will not cope with Melbourne’s cool weather over winter. In our climate you will need to harvest the tubers in May (or earlier if it is a particular cool autumn).
It’s a good idea to take cuttings for planting next summer prior to lifting the tubers. The cuttings will need to be keep in a greenhouse or indoors to protect from cooler weather.
The tubers are located at the base of the main stem. They are very delicate, so carefully excavate around the tuber and lift them. Allow them to dry off outside in the sun on a warm, sunny afternoon. Once dry, place them in an open cardboard box placed in a warm spot for a few weeks to cure. This helps to convert the starches to sugars and makes them a bit tastier to eat. It also allows the skin to harden off, so that the tubers will store better. Make sure rodents can’t get to the tubers whilst curing and when in storage.
Have you grown sweet potatoes before? Have you got any hints and tips on growing them?
I have a sweet potato that has sprouted in mid March, can I still encourage it to grow and plant the resulting shoots later in the year? I live in the Yarra Valley.
Hi Carolyn,
You sure can. You’ll just have to keep the plant protected from frost until the weather warms up in spring.
Good Luck & Happy Gardening!
Duncan
Hi all, i harvested my first sweet potatoe today then sat down to check what i should be doing, so have quickly taken some cuttings and will now let them cure. I was thrilled with my small harvest. I have taken 4 cuttings and wondered what is the best length?
Great information provided, Thank you.
It is nearing April and my sweet potatoes are still full of leaves, are they supposed to die back when ready to harves.
Your advice would be appreciated
Hi Maureen,
I normally wait until the frost kills off the leaves before digging up the tubers.
Happy gardening
Duncan
Thanks for that! I put it in water and within 2 days roots have started growing. At what stage and how will I separate the different shoots or do I just plant the whole sweet potato?
Cheers Carolyn
Once the shoots have developed a few little roots you can pull them off the tuber. Put the shoots in a glass of water to allow them to develop more roots. Then you can pot them up!
HI all,
Well my sweet potato shoots are nearly a meter tall and growing fast. At the moment they are on the window ledge in the kitchen facing a Northern aspect. What happens when the growth is too long to sustain? I’d hate to cut it back. Any suggestions please?
Also where would I get basalt gravel from please?
I got good results growing them in a well composted mound, that also included some -5mm basalt gravel. The dark colour absorbs the sunlight and keeps the mounds warmer for longer, extending the growing season.
Great tip Peter. Thanks for sharing!
Thank you , out of many articles I have read on harvesting sweet potatoes I have found this the most informative.
Thanks for the great feedback Doreen.
Good Luck & Happy Gardening!
Thanks for the great advice. A couple of weeks back we harvested our very first attempt at growing sweet potatoes which was super exciting. We also took cuttings from the vines which are very quickly growing roots in jars on the window sill. Planting time is a good 6 months away so should we be slowing down the growth of these cuttings? ie – refrigerating?
I’m wondering how I’d prevent these cuttings from taking over the planet (or at least my kitchen) if I let them continue to grow so rapidly for a whole 6 months. Any advice would be greatly appreciated.
They are prolific Naomi! Try potting some up and putting them outside. As long as they are protected from frost they should be ok. Perhaps a protected spot or on top of the Hot Water System?
Please let us all know how you get on!
Excellent post well done and thank you
Martin
Sydney
Thanks!
I am growing a crop this year for the first time. I have 4 variety’s in, a friend who has lived in New Zealand has suggested over there the Maori people plant them on a flat 10inch rock which makes the roots spread and produce more tubers, i will try this next season.
Great tip, thanks for sharing Frank. I’ll try this next summer.
Hi, We tried growing sweet potatoes this year. I planted a plant I bought from a nursery in January. It grew really well but when I lifted it there was only one massive potato which was all split. Any ideas what went wrong? How many potatoes would you usually get?
Hi Emily,
we had a similar experience this summer. We planted three varieties with mixed success. The orange variety had many large tubers. The white variety had one plant with loads of medium sized tubers (many split), and one plant without any. The purple variety had no tubers at all. So we won’t be growing purple again!
hope that helps
Duncan
Can i grow them now in tires? Will this help keep them at a warmer temperature?
Hi Claire, our Melbourne climate isn’t warm enough to grow them over the winter. I’d wait until November to plant sweet potatoes. Try to avoid using tires in the garden. They’re full of nasty chemicals and toxins that make growing root crops in them very risky.
Good Luck & Happy Gardening!
Duncan
Thank you for a very informative, useful post. Practical – its April now, but I will plant mine out in the melbourne “sun” under a plastic bag and see what happens
Best of luck with it Alistair. I don’t like your chances, but the plant may survive if you can keep it covered over the winter. We keep cuttings going over the winter in the greenhouse to transplant in late spring
Hi Duncan, I’m in Melbourne.. wondering what varieties of potato you would recommend for growing indoors here, in a heat-controlled grow tent, over winter? My main issue is size, it needs to be as small a plant as possible, and ideally I will be able to get seeds or starters somewhere locally (even at a Northside farmers market or something – if they are still happening with COVID and all that). Hope you can help! I checked with CERES in Brunswick with no luck, they don’t stock them through winter which makes sense I guess.
Hi James,
We tend to focus on working with nature. Growing edibles indoors, in grow tents, using power for lighting and heating the system is a conflict with my personal values and our core business values. As such we don’t really have much experience with grow tents. If you wanted to persist with the grow tent then I’d encourage you to focus on growing leafy greens instead of root crops such as potatoes. See our Philosophy of Edible Gardening Page for more information on why we suggest growing leaves.
In my experience there’s not really any potatoes that have smaller plants than the others. They’re all roughly the same size and if you wanted to persist with potatoes then any variety that you can get your hands on would do.
Good luck with the project
Duncan
Hi James ceres in brunswick had a punnet of seedlings the other day
Hey Duncan, I’d like to ask another question about growing sweet potatoes please. I have just tubed up some sweet potato slips with good root growth on them and they will winter in a new hothouse before planting out in spring. My question is, could I grow them in vertical wire gardens with compost and sugar can mulch layers? I was thinking of making a 1.5 mtr tall garden planting the slips out at the top and as they send out runners, poking them in a little way down the wire garden where they can send out roots into the soil and mulch. Would this work do you think and if not why please.
I have seen the SP grown UP a trellis, which looked very effective, but they were growing them for the leaves not the roots.
I have planted some slips in pots and have put them in the green house over winter. I will try the slips in water inside, as suggested. I was wondering would the leaves of the cuttings in the water be ok to eat, when the plants get out of control? Thanks
Hi Fiona,
I’d imagine the leaves would be ok to eat. They may lack a bit of nutrition compared to plants growing in the gorund.
Stay Safe & Keep Gardening!
How do I take cuttings of the tubers before i take them out of the ground?
Hi Nicola,
Simply cut some of the stems into 10 cm pieces and either plant straight into potting mix, or place in a glass jar of water to develop roots.
You may want to remove some of the bigger leaves from the bottom half of the cutting.
Good Luck & Happy Gardening!
Duncan
Thanks for your advice. I will move my little sweet potato sprouts inside while we endure this cold weather. Looking forward to planting them out in a warm sunny bed and growing some beauties.
Glad you found it useful Jan. Good Luck with the summer ahead!
Hi. I live in northern Tasmania, where we get many frozts. However, I have a hothouse in full sun. I have never seen sweet potato vines and am we ondering how much space should I allow. I placed some sweet potato halves in water and am waiting for results.
Cheers Bob
Hi Bob,
Each vine will easily cover a few square metres. They’re not as prolific as say a pumpkin, more like a watermelon vine in size.
Good Luck!
For the last 8 years I have been growing sweet potatoes , I have grown 4 varieties, orange, light red &! white inside, white outside & purplish inside & 2 years ago I purchased 2 Japanese sweetPotatoes these are dark purple inside & outside. I placed 1 in the soil & it sprouted I got lots of cuttings and planted them
I grow all my sweet potatoes in large pots And I get lots of sweet potatoes, every year
Thanks for the advice Emilie. Good Luck & Happy Gardening!
I bought a sweet potato seedling from bunnings in January but I was late to plant (Embarrassed to say) and it only went into a large pot in March. It thrived and I enjoyed the foliage for stir fries etc. My question is because I’ve now had it over the winter in sydney, would it be too early to dig it up now? Should I wait for some more warm weather in case the potatoes haven’t grown much over the March to August (fall and winter period). Foliage is still growing well.
Hi Kaz,
I really have no experience growing these in pots, or in Sydney, so I can’t give you much advice other than you’ll need to dig it up to find out!
Good Luck & Happy Gardening!
Duncan
Hello
I have a raised garden bed that has grown many sweet potatoes over past two years however this year they are all quite long and skinny and small. I just left allot in the ground to regrow. I’m wondering should I remove all tubers from ground and start fresh this year. I live in east Gippsland
Thanks
Hi Caralyn,
Sometimes I have the same issue. Plants grown as cuttings from the same original plant may have either one huge tuber (my best is 2.7kg) or heaps of small long ones. I can’t work out why. One white variety that I grew was definitely more prone to the long and small tubers. I have no idea why it occurs, perhaps root knot nemotode are to blame?
Is there an option to plant them somewhere else and see if that improves your success? That’s what I’d be doing.
Happy gardening
Duncan
I plant cuttings into a trench with just a few leaves poking out at the end. This allows roots and later the tubers to grow along the length of the stem giving you a bigger crop.
Great tip…. thanks for sharing Amanda!
That’s how they do it commercially in New Zealand.
Hello there, this is such a lovely informative post thank you. I have kept my sweet potato in water since October and after 2 months now have shoots and roots which I feel has taken up much of my garden growing time and I’d like to avoid this next year by saving cuttings. Could you please explain to a complete beginner how one would “keep cuttings” in a greenhouse over winter? Do you just leave the cuttings on a table for example? Or would I have to pot them?
Hi Marilyn, thanks for your question. To take sweet potato cuttings follow these steps:
– Snip some portions of the stem into approx 10 cm pieces
– Strip the leaves (and any side shoots) from the lower 2/3 of the stem (make sure you keep track of which is the top and bottom of the stems)
– Fill a small pot with well drained potting mix
– Push the bottom of the stems down into the potting mix so that the bottom half of the cutting is covered. You could cram over 50 cuttings into a 20cm pot if you like. Always do more than you need as there may be some failures.
– Keep the cuttings moist and as warm as possible
– In a few weeks the stems should start to develop roots
– When you notice roots sticking out of the drainage holes, it is time to pot the plants up into individual pots (or out into the garden if it is warm enough)
Hope that helps speed things up for next year!
Duncan
That’s good advice. I didn’t know you can eat the leaves. My sweet potatoes is growing wild. It taking over all my plants. I didn’t know that I can grow from the cuttings.
When do I harvest it?
Hi Elizabeth,
We usually harvest after the frost has killed off all the foliage.
Good Luck & Happy Gardening!
Duncan
I live in an area with hard frosts so I dig up the sweet potato prior to the first frost.
Because the days can be bleak after lifting them I put them in my oven and turn my oven light on. The temperature then remains around 25°
Thanks for sharing your insight Gloria. Great tip!
Happy gardening
Duncan
Hi, I’m from Melbourne and I love sweet potatoes and I’ve been looking into how to grow them here. Thank you so much for your tips.
I’m glad you found my post useful Jenny.
ManyThanks for your advice , I will definitely wait until the very cold weather comes to harvest, I also have a few small
Cutting that are doing quite well, I will be sure to protect them from the frost.