The rules of companion planting indicate that cucumbers and tomatoes/potatoes should not be planted in close proximity to one another. Let's consider what companion planting is all about first. 1. Companion planting is about creating a diversity in the garden that reduces the chances of PESTs/disease wiping out your garden. So in CP you don't plant things that are prone to the same diseases or attract the same pests close together. In the case of cukes and tomatoes it is: fusarium wilt and powdery mildew. (there could be more things...but this is enough that you have violated one of CP rules). 2. CP is about nutrition in the soil -- that is, you would not plant two things in close proximity that both require heavy amount of any particular mineral/vitamin. So for example if both plants are heavy feeders of potassium -- clearly they would compete too heavily for this resource most likely all plants would not get enough potassium. Cucumbers are heavy feeders and require lots of nitrogen and potassium. Pale, yellowish leaves indicate nitrogen deficiency. Leaf bronzing is a sign of potassium deficiency. Potatoes LOVE potassium, and low levels of potassium cause hollow heart (the middle of the potatoes looks like it is rotting), further the potato plant needs ALL it's potassium at the early stages (BEFORE setting tubers). Potatoes are also HEAVY feeders. Tomatoes are HEAVY feeders. So CP says not to plant heavy feeders next to each other... they compete to much for nutrition. Ok, so now you know why CP says not to plant these plants next to each other. The question then becomes.... but CAN I still do it knowing about the wilt and mildew and potassium and general heavy feeding of all the plants.... SURE, BUT be sure to add lots of nutrition to the soil (compost/manure) add lots of potassium (before planting mainly) and be sure to top up the nutrition during the growing phases... so maybe add manure/compost before planting, mid season and again when fruit starts setting. Also all these plants LOVE water... and lots of it, and this to me, makes it convenient when watering, to have my water lovers all in one spot... that way I can just dump a 5 gallon bucket of water int he middle of them. Also, careful how you trellis the cucumber, you don't want to create a roof over the tomatoes/potatoes that will hold moisture and encourage the mildews.

- Celeste Archer