I'm not sure why you saw advice to plant in something long and shallow :-) There is nothing about the root system or growth habit of blueberries that would require that. The 5G buckets, with adequate drain holes provided should be fine for at least a couple of seasons.

There are both pros and cons of growing it in a container. It will require more frequent watering and regular fertilization than if it were in the ground. Fertilizing can be an issue as you want a low nitrate N source that is also water soluble. And you will need to repot and refresh the potting medium every couple of years as well; also probably will need to do some root pruning at that time as well. The biggest advantage is you can tailor the soil specifically to the needs of the blueberries if inground soil is not ideal.

Northblue is very well suited to container culture, as it is a pretty dwarf plant to begin with. And while blueberries are for the most part self-fertile, you will always get better cropping if you grow at least two different kinds to cross pollinate.

This is what my blueberry is planted in and it loves it.

https://www.amazon.com/Bloem-Terra-Pot-Planter-Cotta/dp/B005J9CTIS/ref=sr_1_26?keywords=fiskars+pot&qid=1585754870&sr=8-26

I read that they have shallow roots and don't need deep containers. Thank you
Embothrium. I will use a regular round pot. My question now is do I use a 5 gallon pot or smaller.

Does anyone know how old this bush could be that I bought?

I am guessing it's about a year old.. does it show signs of growth? usually they should be pretty green and/or very near flowering when you buy them with a good amount of foliage. are those new flower buds? hard to tell. that one looks like it's either dead or spent the winter outside.. could just be might eyesight.

keep in mind that blueberries like acid soil and they usually grow best in very well draining soil (like a cactus/bark mix). also, in containers they need to be somewhat protected in the winter, 7b might be mild so you might get away with putting them in a garage, etc.

5 gallon will last it for a bit, after that it will need something bigger.

I agree, a 5 gallon bucket is a good next step. When I grew them in pots, they grew like weeds, so my 5 gallon stage only lasted a year.

Vaccinium corymbosum gets pretty big, except when a dwarf cultivar is chosen. Regarding 'Northblue' specifically Monrovia for instance calls it a "half high" blueberry, assigns it an "average landscape size" ranging up to 3 ft.

https://www.monrovia.com/plant-catalog/plants/2194/northblue-midseason-blueberry/

'Northblue' is a hybrid (as are all half highbush blueberries) and is a naturally compact plant, only growing 2-3' tall and about as wide. A 5G container will accommodate it nicely for several growing seasons.

I bought the Northblue blueberry bush yesterday from HD. Its still on the cooler side here.

I have another blueberry bush, forgot which variety right now, that I planted in the ground 2-3 years ago. Over the years its barely grown. It produces some flowers that starts to turn into the berry. They either dry out or birds pick at them. Im not sure what I should do for it.

My question now is if I do plant it in the ground how far do I need to space between it and the Northblue? Here are pictures of the one in the ground. (sorry for the bad pictures)

For the one in the ground, remove the grass, debris, etc., from its space. As for the lack of growth, it may be wanting for water, sun, or soil modification. It should be in full sun, and ideally it should get ample water, though not to the point of wet feet, and be in acidic soil to thrive. The shriveling berries sounds the flowers were not properly pollinated; you may have a variety that doesn't self pollinate well, though it could also be a watering issue, as a plant with insufficient water or nutrients could abort its fruit to devote energy to survival instead. The second bush will help greatly with pollination. Birds ... well, they do love blueberries; if you don't want them stealing your berries, net the bush.

If you plant Northblue in the ground with this bush, you want a couple feet between in order to give room for growth without tangling, which can make harvesting difficult, but you want to keep them relatively close in order to improve cross pollination. With Northblue being a half high, I would say probably 3-5 feet apart depending on how big the other plant is likely to get.

Simplest improvement: remove the competition (grass) from its root zone and water it more ... nice deep watering, not just wetting the surface.

More advanced improvement: check your soil pH and add amendments and acidifiers to improve the soil.

Also, if you have deer or bunnies that might be munching the tender growth off your bush, a wire cage can help protect it.

Once the weather warms up a bit I'm going to clean up around it. I neglected cleaning around it once I saw it wasn't going to produce any berries last summer. I found pictures of the containers of the blueberries I bought back then. Its one of these two varieties. Chippewa or Bluecrop

I'm going to guess it's a Chippewa. The Chippewa variety has a slow growth habit, and according to the article below needs a second plant to cross-pollinate with it. Both varieties are relatively small, so you'd probably be fine with 3-4 foot spacing.

https://pss.uvm.edu/ppp/articles/chooseblue.html

We have been growing blueberries for five years now and learned a few lessons along the way. We started with our blueberries in pots. Then we found that the birds ate the berries before they were ripe leaving none for us. Then we built a screened blueberry cage and moved the pots inside. That worked for a few years, but the pots restricted growth. Last year we build raised beds to go in our enclosure and transplanted our blueberries and they are now thriving again. I'll try and post a few pictures.