Why not put each in its own pot and put those pots in the larger? After a year or so, select the more vital plant & do what you will with the other. Pot the selected plant in your 'now likely too large' pot. I'm not a fan of self watering, so I'll leave that to others. Use a soil that drains well. It will already be on the acidic side, but you can lower pH by using an acid forming fertilizer, like MG for azaleas or equal.

Al

Since northern highbush blueberries like that variety require a certain number of chill hours, your bushes need to be out year-round, although if you have a garage or something, they could be moved into that.

The reason why I mention this is because IMHO, ceramic is just not a good choice for large shrubs that need to get through a harsh winter due to their propensity to crack if not properly fired and sealed to keep water out (the water can freeze/thaw and make them crack like terra cotta). In addition, the paints used for ceramic are usually not for food use, and you have a danger - most particularly with acidic soil, of getting excessive lead and/or cadmium leaching into that soil. As a chemist I have tested many samples of dinnerware for lead and cadmium and would get samples of plates, cups, bowls or other vessels that were not only improperly fired, but were decorated with paints not for food use, thus leaching excessive lead and other toxic elements into acidic aqueous media. What might be better is to use a plastic or foam pot and then place that in the ceramic if you want a more decorative container for them. Natural materials such as terra cotta, stone, or concrete could work, but with respect to terra cotta - it's that issue of cracking again - at least over the long haul and shrubs like blueberries are long-lived.

As 6" plants, I would start them in smaller containers until they build up more of a root system and then transplant them to a bigger container. Two of my five blueberries were originally 6" mail order bareroots and I put them in 12" plastic pots and there they remain some 11 years later and are about 5 - 6ft tall now. The other 3 that I have were older plants that came in 12" pots and I have kept them there. And although that size is not optimum, I still get nice harvests of blueberries most years - assuming they bloom when the bees are active and I get good pollination. My 5 are of 4 different types with different harvest times, so I can get some berries all summer through into fall.

I would also keep both plants as that will help give you a bigger harvest. Although most blueberries are self-fertilile, cross-pollination between 2 or more has been shown to give a somewhat higher berry-set. It might be better to pot them separately in any case, although you could try growing them together if you are prepared to increase pot size accordingly. Your harvest may be reduced but then I always say to myself that these are for personal use as I am not a farmer trying to increase production for sales.

With respect to soil - I usually mix up a non-specific type of soiless container mix (recently I've been using Promix) with about 1/2 sphagnum peat to give close to the proper acidity to start and then I'll fertilize about twice a year with Hollytone, which has a slow-release acidifier in it. Blueberries do best in pH 4.5 - 6, although there are a few varieties that can grow okay in that 6 - 7 range, but those are few and far between.

Regarding self-watering - if you mulch with shredded pine needles and/or shredded oak leaves (the oak leaves being a good contributer to acidity), that will help tremendously with not having to water as often. The tricky thing about blueberries is that they can get root rot if overwatered but then they DO need moisture - particularly when berrying. However good drainage and the ability for the mix to dry between waterings (within several days) seems to be best in my experience.

Wow, thanks! Great info. Never thought about the ceramic pot/food connection. Good to know! And that the pot itself needs to hold up in winter. Thank you thank you! And i suppose watering won't be too much a problem if I mulch properly. Can you buy pine needle and oak mulch, or do you have to find it yourself? I have neither tree available!

I have never seen either for sale in my area.

However, depending on where you live (do you have such trees around?) they aren't usually too difficult to come by. In the fall simply visit any property with oak trees and take what they rake to the curb. You can bag it in plastic bags and use as needed. After a couple years anything not used becomes leaf mold which is a great soil conditioner.

Pine needles can be snagged from anyone who has a few pine trees, the soil underneath will be covered with them. Otherwise talk to whomever sells xmas trees in your area. They probably won't mind you taking some needles or maybe selling you them for cheap.

If your area has a pickup for xmas trees after the season you can talk to the park/maintenance folks to see where that goes. You can probably score some there as well.

You really don't require either for a mulch though. There is some controversy as to whether these materials actually acidify the soil. They are acidic, but some studies have shown (suggest) they do not 'leech' that acidity as they decompose. Other reputable sources say they do [shrugs].

You can use most anything and not worry about it and most everything becomes near neutral in ph after it breaks down.

The most important part of managing ph in a container is to regulate the ph of the water it gets. Rain water is naturally acidic, tap water can be acidified with vinegar and there are ferts forumlated to acidify. Use those, avoid ANYTHING with any amount of lime, and the acidity issue is under control.

agree with username_5! I get my pine needles from my mother's white pine (when I have to go over there in fall to rake and bag them) and get oak leaves from both of my sisters who have neighbors with oaks.

username is correct about the pine needles as they don't really acidify the soil although they can be helpful for moisture retention but fluffy enough to get moisture actually through them to the soil underneath. And if you've ever raked up pine needles, it's amazing how rich and black the soil is underneath. With respect to the oak leaves, they naturally contain tannin that can form tannic acid when aqueous, which can help a bit to acidify as it leaches from the leaves as they break down in soil. Tannic acid generally has a pH ~4, although what the pH of the leachate will vary depending on how much water runs through and the water's own pH, etc.

I don't have a very recent picture of my blueberries from a head-on view where they sit between 2 lilacs, but here were the flowers from them in April looking sideways at them with a rail-view perspective:

{{gwi:31738}}

This is a closeup of the above picture (the biggest clusters visible coming from what I bought mailorder as 6" bareroots called "Patio", which are my oldest blueberries at about 10 years old in their containers):

{{gwi:31739}}

These were not "dwarf" plants (which are commonly sold for "patio" growing) as I would come to find once they matured, so I am trying to find out what they really are. They produce small, very dark and sweet blueberries, with clusters that ripen throughout the summer and I have 2 pots of them. The other 3 varieties that I grow are 'Bluecrop', 'Elliott', and 'Nelson'.

I was very heartened that so far that I can tell, most of these flowers actually got pollinated and are forming berries. Heartened mainly because they bloomed a bit earlier than normal due to the mild winter but during the period when the flowers were fully opened, the temperatures were marginal during the day for good bee activity (low to mid 60 Fs) - at least up in the sky where I am. I usually have to rely on the carpenter bees to do my blueberry pollination as I don't usually see bumble bees up here until later if they even bother coming up. Although... I have been seeing more honey bees or similar each year, usually as solitary scouts, so that's good. Unfortunately, I caught a carpenter bee this morning actually chewing a hole in my broom handle... !!!!! First time I saw that happen and can see why they are also considered pests. I actually watched the thing as it chewed and sawdust was dropping out of the hole it was making (it had chewed through the paint too and usually it's recommended that wood be painted to discourage them)! I don't have much wood out there other than a few stakes, a couple small cedar planters, and the brooms and shovels, so until now, those bees have been more helpful than hindering! LOL