I am a newbie polytunneler in NW Ireland. I have been amazed at the prolific growth of almost everything we planted. Having read the questions on the height of runner beans, is the prolific leaf growth on cauliflower, broccoli, and cabbage detrimental to the vegetables we wish to harvest?
On cabbage, I would never consider excesive leaf growth bad, since it's the leaves you are eating in the end. The more leaves, the larger the head will be.
On broccoli and cauliflower, I wouldn't consider it a bad thing either, even though you aren't eating the leaves. The plant is getting plenty of nutrients, and growing like it should.
I agree with Thomas, but there is a school of thought that removing leaves, leaves more nutrients for fruit (edible parts).
I read a forum where people were arguing whether a pruned or unpruned tomato plants were better. The argument ended with the statement that the world record total weight of fruit produced was grown on an unpruned plant. The statement wasn't challenged, and since it jived with my current thinking, I accepted it as fact without further research.
Now, thinning the fruit will produce bigger remaining fruit, but I don't see why removing leaves would.
So after I typed all this, I decided to do just a quick search because I hate to say something that is just my opinion without some proof to contribute... I found this:
Fresh market tomatoes were evaluated at the Pinney-Purdue Agricultural Center in Wanatah, Indiana. Nine beefsteak types and one roma type were evaluated in a replicated trial. Plants were grown with and without pruning to evaluate pruning effects on yield and fruit quality.
Pruning made a large difference in No. 1 yield, total yield and fruit size (Tables 1 and 2). Averaged over all beefsteak cultivars, pruning reduced yield of No. 1 fruit and total yield by 38%, and increased fruit size by 25% (Table 1). Last year results were similar: No. 1 yield was reduced by 40% and fruit size increased by 19%.
Results for additional pruning treatments on Mt. Spring, SunChief, and Mt. Fresh, are shown in Figs. 1, 2, and 3. Yield of No. 1 fruit as well as total yield was greater for unpruned plants than for pruned plants (Fig. 1). The heavier the pruning, the less yield. On average, for each branch left on the plant, No. 1 yield increased by 1.75 lb.
Effectively, by pruning a tomato plant, you're removing fruit (thinning fruit) before it develops. So this would fall into the thinning category, not removal of just leaves.
I cannot find evidence that removal of leaves will affect yield either way.