It's been a journey with my turnip growing but roughly two months after being sowed, I started to enjoy eating the first of these wonderful and nutritious little roots. What is more unique about this experience is that I planned right from the start to grow these in containers. These are normally grown in the ground or in raised beds but I wanted to see how well they would fare in a confined growing space.
It was a struggle to find much in the way of useful information on growing turnips in containers. The common issue that came up across a variety of gardening forums was how this particular vegetable crop hates having its roots disturbed.
There were some setbacks with growing these but this heritage variety, Manchester Market (also known as Green Top Stone) were pretty resilient despite all my re-potting into larger containers as they grew and all the knock backs from various pests. I ended up with a good crop regardless.
Sowing Seeds in Individual Modules
I grew these young plants initially in individual modules from seed. They were kept covered with a clear, plastic lid to retain warmth until they started to germinate. At this point, I removed the lid during the day for necessary ventilation.
After growing these initially in small modules, I then potted them into 9 cm / 3.5 inch width plastic plant pots. This is a good size for young seedlings and you can see some of them potted up in the photo.
Most of the turnip plants were potted on to this size pot just a few weeks after sowing, so they are definitely quick growers. I kept the pots in these larger trays for easy carrying in and out of the polytunnel. Overnight and during bad weather, they went back under cover for added protection. My daily routine was to give each pot just a little tap water so that the compost was damp but not saturated.
Damage to Young Growth by Vine Weevils
The photo here is a good example of why it is a good idea to cover young plants with netting such as Environmesh or similar. Here you can see extensive vine weevil damage to this young turnip plant. There are tell-tale holes and imperfections. One leaf has been so badly infested that it has shriveled up.
Adult vine weevils love to eat leaves and especially those on seedlings and young plants. They can't fly but they can crawl an extremely long way. Almost nowhere that you put your plants is safe from an attack unless you have suitable netting or protection over the top. I wrongly thought my containers would be safe because they were always raised up off the ground. Sadly I was wrong.
You can often see vine weevils on the underside of leaves. They look like very tiny and dark little beetles. If you see them, you really want to either pick or shake them off. The adults can do a fair amount of damage to young plants as you can see above but the larvae that they can lay are even more destructive because these go on to eat and damage the roots. On turnips this is not ideal since it is the roots that you want to eat.
Once I noticed the infestation, I checked my turnips at least daily. I either picked or shook these pests off, making sure to check under rims of the pots and around the bottom, until I got the problem under control. Thankfully most of the young turnips did recover from this. The Royal Horticultural Society have more vine weevil information available. 
Using Grow Bags as Containers for Turnips
Once it looked as though the turnips had outgrown their pots, I made the last re-potting into some Hadopots about a month after sowing. Hadopots are growing bags which you can use for plants. For the turnips I used grow bags that were 8 inches tall and 6 inches wide.
Due to the lack of information available, I wasn't really sure what final size of container to use for turnips but I figured that I could always re-pot larger if this wasn't right. I then placed these bags into large plastic tubs which I could move around better to get the most sun in the garden.
One of the best places in the garden, I found, was the gravel drive to the back of our house. This is because the slugs and snails seemed to have a much harder time getting into the containers and damaging the plants. A few managed it and I picked them out but there were far less than when placed on the grass. I should imagine that these creatures don't glide quite so easily over gravel. At this point, these containers were left outside no matter what the weather. I gave them a little water every day unless it rained and the compost felt wet enough.
For growing turnips I would look for a minimum size of 5 gallon bags going up to 10. Bear in mind that you may need to move yours into larger plant bags depending on how well they grow. You can eat turnips while the roots are quite small and very often they taste better for it.
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Cabbage Root Fly Maggot Damage to the Roots
This is why you really need to protect crops with something like a fine Environmesh! This was the damage caused to one of my turnips from cabbage root fly maggots. These grubs tunnel into the juicy flesh of the root which completely spoils it and makes it inedible. Luckily this was one of just a few spoiled by this pest.
The fly looks like a normal house fly but it lays larvae which can eat the roots of the plant and tunnel into root crops such as swede, turnips and radish. You can help to prevent infestations by covering crops with fleece, fine mesh and by making protective cabbage collars which are circles or squares placed right around the base of the stem, These protective collars stop the fly laying eggs near your plant. The Royal Horticultural Society site provide information on this pest. 
Simple Method to Help Deter Cabbage Root Fly
Harvesting and Eating the Turnips
Despite all the issues these poor turnips went through, it surprised me what great growers they have been. Roughly two months after first sowing the seeds, I began to harvest and eat this Manchester Market variety.
I picked mine once the roots showing at the top of the soil measured about 2 - 2.5 inches wide. If you let them grow too large, they can take on a woody taste. At this size they are really lovely peeled, diced and steamed until tender and then eaten with a little butter melted over the top.
You can also eat the leafy tops which are abundant in growth. I might well have done if the leaves had not been attacked and eaten so much by caterpillars laid by Cabbage White butterflies. That is another good reason to cover this crop up with mesh.
Are Turnips Worth Growing in Containers?
I've really enjoyed the flavor of this heritage variety and how easy and fast these have been to grow. I can imagine that by learning lessons from this year about covering these from the start then I can expect a near perfect crop when I grow them again. These were definitely worth the effort and they did work well growing them in containers.
The only big issue is that you need to grow a lot of these to get much to eat from the roots. For container growing in a limited space this is a little less practical. They are probably best grown in the ground for this very reason.
Image Credits: The introductory image belongs to the author, Marie Williams Johnstone. All other images (unless watermarked with the author’s name) are product photos from Amazon.