Part of the Sweet Potato Harvest.  15kg from the best pot!

If you want to know how I managed to grow a whopping 29kg of Sweet Potatoes from just 4 pots, keep on reading and I will tell you how I grew a fantastic crop this season.  

I have had consistent success with growing sweet potatoes over the last couple of seasons in a garden bed, but I have never really been satisfied with the amount of space they took to grow.   Plus, I need to be constantly trimming them back to stop them from taking over the whole garden as they grow.

Last season I started to grow them up a trellis to give the vines somewhere to spread. It not only looked great, it helped to increase the yield and I no longer needed to trim the vines to keep them under control. 

To give me an extra growing bed I thought that I would try something different this season, to grow them in pots.  After my previous seasons growing successes, I thought I had a good chance of it working out OK. 

Lush mid-season vine growth

The season is now over and it is time to share with you what I did to get such a great crop and what I will be doing to improve for next season.  Keep reading to discover how I grew them.

Soil

Sweet Potatoes are heavy feeders, so I used a premium potting mix for two of the pots and the contents of one of my compost bins for the other two.  The compost was at least a year old and the local worms had completed a marvellous job of turning all the garden and kitchen waste into a brilliant rich soil. 

Pot Size

I chose four of the biggest pots I could find in the local Garden Centre to grow them in, I looked for quality pots so I could use them many times.  They are 50cm high by 50cm across which equals a capacity of 98 litres of growing soil.  They proved to be a great size and were still light enough at the end of the growing season for me to pick up (only just)!  Worth considering your ability to lift them when you buy.  

Fertilizer

When I first filled the pots, I added a cupful of pelletised chicken manure and half a cup of rock minerals and mixed it in well.  As the crop grew, I twice more threw onto each pot another half a cup of pelletised chicken manure and gave them a drink of liquid manure every month as per the strength recommendations on the pack.

Location

They all grew in full sun throughout our hot Summer. Because the pots were black, I shaded them by placing them next to a hedge and once they were growing, they provided their own shade as well.  I covered the top of the soil in each pot with 6-8cm of sugar cane mulch to keep the weeds down and surface cool

Watering

I watered daily using bore water which is controlled by an automated watering system, so they never missed out.  I use two drippers per pot just in case one of them decided to get blocked which happens frequently using bore water.  The aim was to keep the soil moist but not too wet, and any excess water drained out of the pot.

Support

Each pot had a wire trellis 1.6m high and 1.2 wide.  I bent it vertically down the middle, so it was at a 90-degree angle and secured it into the pot with a couple of stakes and ties.  The vines needed a bit of training when they were young by simply threading it through the mesh and I would occasionally have to poke the odd vine into the mesh when it was heading in the wrong direction.

Planting

Pot one was planted 30 September using cuttings that I took mid-April from the previous seasons planting.  I over wintered the rooted cuttings in one of the garden beds and they were transplanted into the pots.  Pot two was planted on 20 October from slip cuttings grown from a tuber that I grew indoors suspended over water to shoot.  I put the tuber in water early Sep and planted 10-15cm slips.  Pot three was planted 10 December also from slip cuttings.  These were from sweet potatoes that were still in the pantry that decided to regrow. Pot four was tip cuttings taken from the vines growing in the first and second pots and it was planted 20 January.  

Pots one and two were planted in the composted soil while three and four were from premium potting mix.

All the plants I grew are a variety called ‘Beauregard’ and they were from the previous seasons crop that I harvested in May.  I planted four plants into each pot.

Harvesting

When the vines started to yellow, and leaves began to shrivel on the vine it was time to start harvesting.  What I found was that regardless of the timing of the planting all the pots continued to grow until Autumn and the vines all started to yellow around the same time.  All were ready to start harvesting from the first week of April, however I waited until June to harvest because I wanted to give them the longest possible time for all of the goodness to be drawn down from the dying vines into the tubers.  I would have waited a bit longer, but I wanted to use the pots for the next crop.

Harvest results

Very mixed results from each of the plantings.  Pot one 4.5kg, Pot two 15kg, Pot three 6.5kg and pot four 3kg.  Overall, I harvested 29kg from the four pots and I am delighted with the result.  Considering last year, I was incredibly happy when I harvested 18.5 kg from a garden bed 1.2m by 2.4m this is absolutely a cracking harvest!  

Conclusions

The compost was much better than the potting soil by a long shot because it was able to retain nutrients in the composted soil better than the potting mix.  The cuttings I over wintered in pot one did not do very well, they never grew with vigour and were soon overtaken by the slip cuttings in pot two.  Pot two and three were slip cuttings and they took off as soon as they were planted and never looked back.  Pot four was tip cuttings that were planted directly into the soil in the hottest time of the year and they did not respond well for several weeks. Their growing season was also the shortest because of the late planting.   

Lessons learnt

I think for my climate on the coastal fringe of Newcastle NSW the best planting window is from mid October to end November.  Planting four slip cuttings per pot worked well. They should be 10-15 cm long and grown from a tuber that you put over water (give yourself a 6-8 week lead time for the potato to shoot).  Plant them in a pot that is full of compost, with added rock minerals and pelletised chicken manure. Fertilise as they grow with more pelletised chicken manure and liquid manure.  Mulch with sugar cane and water regularly throughout the growing period to keep them moist but not wet.  If you water too much when growing in pots you will wash your nutrients away.

Next year

I will be doing this again next year.  Four more pots should be more than enough I reckon and, I will be aiming for at least 40kg for the season.  I reckon I might just be able to do it as well, are you game to join me and give it a go?  

If you prefer to grow them in a garden bed, read how I have grown them in past seasons in this blog.  Also, if you are wanting some personalised advice on growing veggies or how to set up a garden check out the consultancy services that I offer or feel free to contact me using these methods.

Who is up to the challenge next year?  Join me as I try to improve my harvest total.