Here's my two-cents...

I would plant on 16-18 inch centers in rows parallel to your house, instead of 24 inch, and leave more space between rows so you can walk through them to tend/cut. This would allow you room to put tomato cages on each one, or stakes, and you would be able to further support them by tying each plant support to the one next to it, providing additional structure to prevent toppling.

You might want to leave a bit more space next to the border, as the plants will expand onto your lawn the way you have it on your diagram. Happens to me every year on some rows where I slack on the spacing to the edge, and hubby is not a fan of the swerving he has to do with the lawnmower.

You might also want to consider buying 2- 50 foot 'leaky hoses,' and have a manual timer with a 2-way splitter on your spigot. You can run the hoses down each row, on either side of the main path, and set the timer for 15 minutes 3 times a week. There is something to be said for being able to WALK AWAY being assured of even and deep watering. Be sure to cover the leaky hose with mulch... the sun is bad for them, and there will be less evaporation if soil & hose is covered.

I'm sure others will have different thoughts, but hopefully this helps.

Cheers!

CiCi

Thank you Cici! Your answer finally got my brain over it's stumbling block. I kept staring at the space and was stressing over what to do. Last night I took some small bamboo stakes to mark my spots and i think I have. (I have larger 7 foot stakes going in for the actual planting time)

Do you think 3 feet or 4 feet in between each row is better? Right now I have them marked at 3 feet in between rows and each row is spaced out 18 inches apart.

I have seven feet between my rows, and if I do a poor job in staking, the 56" lawn mower can't make it through. Four feet from edge of row to row would be as close as I would go, if the pathway was mulched and not grass.

Are you measuring the row from the plant center, or 18" out from plant center?

Personally, I would plant the back row no more then 16-24" from the house. You don't need to go behind the plant, and you are planning on irrigating, after all...

You might also consider making a double row 18-24" away from each other to save space. No need to go between them as long as you have access to each side, and you could tie twine around the double bed after tying them individually. If you have the room to do single rows, then that's great. But not necessary.

Here's a double row in a soft raised-bed, with leaky hose irrigation put down before the mulch.

I'm so confused now! lol. I think I'm making this harder than it should be.

So it seems like I probably shouldn't have 4 rows that are 3 feet apart (meaning 3 feet away from each plant's center.)

I could do a double row but that means I'll only get about 20 tubers in that space. Is your double row 18 inches from each plant center? And then what about the spacing in each row? Those look pretty close together.

My plan was to work on them today but it's raining and tomorrow I have my Barry Manilow concert to go to :) so I can't be in the garden all day. Decisions...decisions.....lol

I agree with Cici, you want to make sure you have enough room to maneuver around the plants once they are fully grown. You will have to access them to cut the blooms and keep them flowering, and to tie them up. They seem tiny now but those beauties will be huge by fall. As CiCi said, you could plant a "double row" which is very close together, and give yourself more space in between the rows to walk. Another trick is to plant 3 of the same variety together in sort of a circle, with a stake in the middle. I tie all three together. It takes up less room than having each plant spaced out, and you still get a lot of flowers. Do you have 40 different varieties that you are trying to fit in, or just 40 plants, some of the varieties doubled up? My advice is to plant a few less, and let them breathe more. I plant mine about 24-30" on center, and the next row 24" away but staggered, but I have straight 5' wide beds that I can access from either side. I used to have a bed like yours but it got so hard to get in there I moved all the dahlias out into their own bed. Its a growing obsession

Thank you so much Cici and J Pru! I was able to get them all in and because of your feedback I significantly (and reluctantly) changed my spacing, I was trying to get way too much in that space. In the end I only got 22 tubers in.

Now, fingers crossed that all the rain we have gotten since going in the ground last week doesn't rot them!

Not sure how big your tubers were but you can always put two tubers in the same hole, especially if they only have one eye. That way you will get more tops from "one" plant.