Plant two for pollination: but in cramped spaces, can I plant them right beside each-other?

Spring planting has begun, but in our tiny yard we're running out of places!

Dwarf trees, edible shrubs, and a commitment to prune other trees to smaller forms have all come into play. Some trees are grafted varieties with multiple cultivars on the same tree for self-fertilization, but these aren't always available for every uncommon fruit.

I've got Jujubes and Pawpaws to put in the ground. I only have room for one tree of each, but I bought two cultivars for pollination. I know all the guides will say give ample space for individual growth, but what happens if I plant the small trees 1-2 feet apart? I know they'll interfere with each-other's growth, and I'm okay with that - as if they are one entity. Ideally I would graft some branches from one cultivar to the other in case one of the trees dies to ensure proper pollination, but the start of this journey would be getting roots in the ground in limited space. What can I expect if these small whips are planted very closely over the long term?

I'd try approach grafting with the whips side by side, because it provides a good success rate and a hedge against failure. Even if one of the rootstocks eventually gets out-competed, you've got the tops of both trees.

I think your plan of putting them 1' apart would work just fine.  I planted my butternut trees 8' apart since I had the room.  They'd prefer 50'.  But in the woods there are plenty of canopy trees with trunks a foot or two apart.  Sure they aren't as big as they would be but cumulatively maybe they are?  In any case, they can handle it in the wild so why not in your yard.

Seems like a win-win-win idea.
One or both might be stunted,  but you need them to stay small anyway.
If one is dominating the other, you can prune accordingly.
Maybe plant two dissimilar trees next to one another, to counter the spread of disease and pests.
Maybe splice early and often to ensure varietal survival.

I have a yarden that is small and the soil is full of rubble.
I just today decided to put multiple plants into each hole, because digging a hole there  is REALLY difficult.
Today it was a a bunch of volunteer seedling  that I added to a hole along with a willow stave.
Maybe I'll drop a nitrogen fixer in a hole with a grape vine and a dwarf chinkapin oak, or a  pear tree and an almond.

I'm told that yes, you can do this.

A friend of mine who is very familiar with orchard things told me that if you have limited space, you can plant three chestnut trees in a triangle fairly close together. They will adapt and learn and still likely have plenty of sunlight depending on the site. That's just an example. I've also heard of people planting male Chinese mulberries and female Chinese mulberries in the same hole, to save space.

Thanks so much for all the valuable feedback here everyone!

Where possible I've planted self-fertile cultivars of Persimmon, Che and others and stayed away from trees that required more genetic diversity. Great to know I'll be in business with my new arrivals planted nearly in the same hole! :)

In fact, pawpaws are a grove forming tree and are said to link roots and share nutrients, so they might be well adapted in particular to that.

James Landreth wrote:In fact, pawpaws are a grove forming tree and are said to link roots and share nutrients, so they might be well adapted in particular to that.

Fascinating, James! Do you have any research / documentation on this?

One green world talks about it here, under "Plant Spacing." I believe I've heard it from a friend who does a lot of food forest work though:
https://onegreenworld.com/pawpaw-growing-guide/