Actually two plants of the same kind could grow right next together! It depends on the gardener to provide the needs of food and water for the two, as if it were a large single bush. I'm hesitant to jump onto another accepted myth: competition. The latter starts only when the least available resource becomes a limiting factor...if there's enough water, light and food for both specimens then there's no competition. If you have a climbing grafted bush and also a low bush next to it, their roots might eventually intermingle....so what?....as long as there's enough nutrients in the soil for both. With present chemical fertilizer alternatives, even with generous ammounts of manure and compost ( like three inches of these piled up regularly on top) I doubt that your bushes growing together will ever suffer then from nutrient competition. Your watering needs is a different issue. Some people upturn bottles with small holes in their caps as alternatives to a drip system. I can only guess how much, but perhaps two bottles a day of 2.25 lts fizz bottles could serve that purpose. I have a colleague from our ag school who lives in warm/hot Salta and his very large property rural was beyond installing a drip system. He had his roses, irises, and daylillies watered thus. My 2 cents in helping you out in your present conditions....
Arturo
