Last summer I decided to conduct an experiment in my greenhouse, to see which varieties of tomatoes would grow and produce best, and in which of 5 growing mediums, in response to lively discussion on a Facebook group I am part of. I carried out the experiment, but was rather remiss about actually publishing the results, so here I will link each of the YouTube videos, plus add the results and my comments, so it's all in one place. If you are just after the results, scroll down.
So, first, this video explains the experiment and set up (why You Tube insists on using the sheep for the thumbnail....??):
So, first, this video explains the experiment and set up (why You Tube insists on using the sheep for the thumbnail....??):
On November 26th I made a video update, in which I commented that there was already some signs of plants in some mediums doing better than others.....
I actually ended up sending an email to the company that produces the potting mix and compost, and as a result had a visit from one of their regional managers, who was interested to see what was going on. By the time he visited, the plants which were in the compost, which had initially done much better, were slowing down somewhat, and the plants in the potting mix, which seemed to have deficiencies at first, were doing much better. This is logical when you think about it - the compost provided initial burst of nutrition, which then got used up, while the potting mix contains slow-release fertilizers, which took a while to kick in.
However, as the summer heat kicked in, and humidity in the greenhouse rose, the plants all got blight. Despite this, many of them continued to produce well. I shot two more videos, which I have combined into one you-tube clip: updates from 1st February 2015 and March 16th 2015.....
However, as the summer heat kicked in, and humidity in the greenhouse rose, the plants all got blight. Despite this, many of them continued to produce well. I shot two more videos, which I have combined into one you-tube clip: updates from 1st February 2015 and March 16th 2015.....
A note regarding feeding the plants - initially I started off feeding the plants with fish suspension liquid, and then later some worm tea and/or Seasol. Anytime I fed them, I fed all of them the same. However I did not continue this regime for terribly long - getting too busy with other things. Obviously, if I had consistently fed the plants, they would likely have produced more than they did. But either way, they all got the same treatment, so for purposes of comparing growing mediums and varieties, there are still things we can learn from this very unscientific experiment.
Tomato Experiment Results
The main results I was looking for were actual tomatoes produced. So, as I picked each time, I weighed the resulting fruits and wrote them down under the # of each bucket, and at the end collated the results.
I'm going to group the results two ways - first by variety, and then by growing medium. Weights given are in kilos, and are the total harvested weight from the given plant in that bucket. The easiest way for me to do this is to create tables in Word then import them as images - apologies if they are a bit fuzzy.
I'm going to group the results two ways - first by variety, and then by growing medium. Weights given are in kilos, and are the total harvested weight from the given plant in that bucket. The easiest way for me to do this is to create tables in Word then import them as images - apologies if they are a bit fuzzy.
Total harvest by variety.
(I) stands for Indeterminate variety - keeps growing like a vine.
(D) stands for Determinate variety - grows into a bush, produces, then dies off.
(I) stands for Indeterminate variety - keeps growing like a vine.
(D) stands for Determinate variety - grows into a bush, produces, then dies off.
| 100% Potting Mix  50/50 Potting Mix/Compost Mix  For this last set of buckets, a thin layer of topsoil was placed in the bottom of the bucket, then 1/2 the bucket was filled with fresh sheep manure, and the top 1/2 with compost.  | 100% Compost  50/50 Compost/Topsoil Mix  |
Conclusions
What conclusions do I draw from this experiment? Well, on the face of it, straight potting mix produced the most tomatoes, after a slower start, with straight compost not far behind. If the Roma in potting mix hadn't died, there might be a bigger difference.
No matter what growing medium one uses, though, consistent feeding over the life of the plant is the key to maximum returns!
Of course, one can't really draw final conclusions from this little experiment - to do that, one would need to grow more plants of the same variety in each growing medium, and have some in different conditions (eg outside as well as in the greenhouse).
What am I taking away from this personally? I won't be growing Roma or Silvery Fir Tree varieties again. Moneymaker is a good, reliable producer, but needs proper trellising set up to support it, and regular pruning/training. I don't personally like Box Car Willie as I don't like big, beefsteak type tomatoes. I do like Tigerellas, a stripey heritage variety, but again they need good trellising.
Growing in the greenhouse for some reason (possibly the very high temps at time) prevented the plants from getting infested with tomato-potato psyllid, which devastated my outdoor plants.
This summer I think I will grow just 2 Moneymakers in my greenhouse, in bigger pots filled with a quality potting mix, with better trellising and regular feeding. I will also grow some more smaller pots of determinate varieties Tiny Tim and Sub Artic Plenty. If I grow any outdoor tomatoes, they will have to be carefully covered in micro-mesh to keep out the psyllid. And maybe I'll also experiment with some other varieties. After all, where's the fun in gardening without some experimentation with new plants and/or ideas??
No matter what growing medium one uses, though, consistent feeding over the life of the plant is the key to maximum returns!
Of course, one can't really draw final conclusions from this little experiment - to do that, one would need to grow more plants of the same variety in each growing medium, and have some in different conditions (eg outside as well as in the greenhouse).
What am I taking away from this personally? I won't be growing Roma or Silvery Fir Tree varieties again. Moneymaker is a good, reliable producer, but needs proper trellising set up to support it, and regular pruning/training. I don't personally like Box Car Willie as I don't like big, beefsteak type tomatoes. I do like Tigerellas, a stripey heritage variety, but again they need good trellising.
Growing in the greenhouse for some reason (possibly the very high temps at time) prevented the plants from getting infested with tomato-potato psyllid, which devastated my outdoor plants.
This summer I think I will grow just 2 Moneymakers in my greenhouse, in bigger pots filled with a quality potting mix, with better trellising and regular feeding. I will also grow some more smaller pots of determinate varieties Tiny Tim and Sub Artic Plenty. If I grow any outdoor tomatoes, they will have to be carefully covered in micro-mesh to keep out the psyllid. And maybe I'll also experiment with some other varieties. After all, where's the fun in gardening without some experimentation with new plants and/or ideas??
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