Which zone has most potential for variety?

I was wondering and thinking about the different zones. I lived in Hawaii and loved the year round gardening it was awesome. I also loved the bananas, mangoes, and fresh coconuts.

Although some fruit and veggies from colder temperatures are also great.

I was thinking what would be easier/ simpler; to make a cold zone warm or a warm zone cold. I am not trying to make it snow in the desert, but to create a huge variety of plant life in a certain area.

I would think it would be easier to make a cooler place warm, but thats just a guess. It seems that the more diversity is in a system the healthier it would be as a whole. A zone around 7-9 seems to be ideal for great diversity, but i dont really know, there are a lot of factors

A Mediterranean climate in Zone 9 probably gives the most possibilities for different kinds of plants.  Somewhere it gets neither too cold nor too hot, with a good amount of sun.  One can grow both temperate and subtropical fruit in such a zone, with possibilities to grow tropical fruit as well. 

Steven Baxter wrote:I was thinking what would be easier/ simpler; to make a cold zone warm or a warm zone cold.

I'm pretty sure that it is much easier to make a cool zone warmer than a hot zone colder. Thermal mass is probably your friend in both cases, but I think there are easy and sustainable ways of making heat; cooling is more tricky. You might achieve some cooling with shade and water, but I think frost would need refrigeration perhaps.

Here in NW California, which Luther Burbank called “the best place in the world to grow fruit”, we have zones 7-10 within a very short distance of each other due to the moderation of the Pacific alongside steep coastal mountains. We can keep many subtropical plants alive on the coast, but they need extra heat and light to fully fruit. Inland about 7mi at 1700ft,  we can keep those alive through moderate cold (23f low in last 5yrs) thermal mass elements like ponds, boulders and passive solar greenhouses, and get the sun and heat to ripen many subtropical plants. Both coast and mountains get  over 1000 chill hours to get any stone fruit or blueberries to set and ripen. These factors, along with diverse soils, makes this the second most botanically diverse place on in the continental US. The old growth redwoods also host the highest soil biodiversity. Each giant tree is akin to a Galapagos Island unto itself with endemic soil species in each individual, living and evolving on their massive limb shoulders in the canopy.

I love the concept of micro-climates:

https://permies.com/t/22575/permaculture/Ways-warming-soil-temperature-creating

I'm with Tyler, zone 9 is probably the best for variety and year round garden potential.  I'm in zone 8 and, while we can grow a lot here, there are more things I could grow if I was just a tad warmer in the winter.

I am going to jump in here and suggest a cooler climate might be helpful.  I was thinking about zone 6.  That zone has a long growing season but still has a cold season for those fruits that need chill hours.  Specifically I am thinking about peaches.


Eric