Well, you should be in USDA zone 5 - right? 'Top Hat' is listed as hardy to zone 4, so you should only need to give it a little protection. I would simply bury the container up to the soil line, or a little deeper, on the north side of a building & call it good - unless you want to wrap a little burlap around it to help guard against dessication. Remember to throw a little snow on it from time to time if you think the soil might be drying out or it's sheltered from rain/snow.

Al

Thank you! It's hard to tell from the little map if I'm in 5 or 6 - let's say 5 to be safe. But I don't have a place to bury it - that's why all my plants are in pots on the deck. Everything but the Top Hat are annuals, so I pull 'em & start over each spring. Is it enough to leave it out in the pot (a 10" azalea size terracotta pot) on the north side of the house? In the sun? Wrapped up? Inside a bigger pot for protection? This is my 1st outside plant I need to fuss over. I'd hate to lose it, though - I want blueberries! :)

Can you put it on the north side & pile some leaves up around the container? If you do that - remember not to let it go dry because it will get no ground moisture. I'm sure it would appreciate a little burlap (or an old sheet) as a wind break, too. Avoid a sunny location if you can. ;o)

Al

BTW - this site has a zone finder if you're curious/interested. Just enter your zip & you're good to go.

Al

Here is a link that might be useful: Click me & I'll show you what Al's talking about ...

What a clever link! Turns out I'm in zone 6, after all. OK, I'm going to wrap it and leave it outside against the house, out of the sun on the north side. The leaves are turning yellow & dropping, so I think it's getting ready to sleep. I'll remember to keep it watered. Thanks for all the advice!

Good job! I bet everyone that reads your thread is wishing you well. I know I am.

Al

Next spring, I'd give some serious thought to repotting your blueberry into a larger container. A 10" azalea pot is just not large enough to accomodate a blueberry successfully for anything long term, even a dwarf. It's barely the equivalent of a nursery 1 gallon container, about the minimum size you will find blueberries for sale. For long term container growth, I'd look at 3 or 5 gallon containers, nothing smaller. 'Top Hat' is known for great, bright red fall color - that the leaves are just turning yellow and falling is an indication the plant is under some stress, probably from overly cramped growing conditions.

While blueberries are self-fertile, a single bush will not produce many berries (don't believe those photos showing this little plant laden with berries - ain't gonna happen!). For good cropping, you'll need a second, different type for cross pollination.

I have three top hat dwarfs on my porch in containers. I see you mention that for good cropping next year, I will need a second different type for cross pollination. Are there any you would suggest? Since I rent, what ever you suggest will need to be able to grow well in a pot.

Thanks

You might want to search out 'Sunshine Blue'. This is a dwarf blueberry very suited to container growth and has the added benefit of being mostly evergreen as well. It's a heavy producer, so between it and the Top Hat, you should have a good crop. Sunshine Blue is not as hardy as some blueberry cultivars but is well suited to zones 7 and 8.

Here is a link that might be useful: blueberry 'Sunshine Blue'

Sorry to bring a somewhat old thread back up, but one: I want to make sure that AllisonW posts how the tophat is doing when spring comes around (And right now, it feels like spring here with a nice sunny day, and 45º weather), and two, I got a couple of tophats myself around last July, and they're the first plant I've ever had to worry about being outside (I've never had my own home, and thus, never a "real" garden. Instead, I have a bunch of potted plants [Mostly annuals] in my bedroom, and my blueberries are the first I've ever had to leave outside ^_^;;)

I've been worried about how I left my blueberries out during the winter - since they're in pots, I figured I shouldn't let them sit in the ravages of the winter, since I thought the wind might be too cold and freeze the roots (I live in Zone 5 according to all zone maps, but that link posted in here says I'm Zone 6, which seems odd to me, because I'm in Illinois, only a few hours south of Chicago...)

So, as soon as they dropped all their leaves (Which did turn that gorgeous red color :-3 ) I put them in the garage, to keep them out of the wind. Every now and then I would put some snow in the pots, but since there were times I was gone, once for over a month, I wasn't able to check on them as much as I'd like... I'm hoping that they didn't dry out and die >_But assuming they didn't, when should I bring them back out again? After the last frost date? As I said, right now it's a beautiful day out, but the 15 day forecast does show the wind chill getting as low as 10 degrees in a week or two, and I dunno how hard that would be on the plants - I have no clue what they can and can't take - I'm completely new at wintering AND blueberries.

Thanks for the help ^_^
And thanks to Allison for posting this topic - I learned quite a bit from it :-)

Put the plants out as soon as you see the buds swelling (at the latest). This means leaves are about to emerge and once this happens they need light.

If it's hardy to zone 5 that means it's theoretically hardy to -20F, but in containers the usual rule of thumb is to add 2-3 zones to it's hardiness. A zone is 10F different from the next. So if we figure in a container it's hardy to zone 7 or 8 that should mean 0-10F. If the nights are above 10F it should be fine to put outside with no protection.

Here's the problem with over-wintering our deciduous containerized material in buildings: They ALWAYS leaf out too early, and this is a clear disadvantage. The reason for the disadvantage is that buds respond to rising sap, stimulated by a few days of soil temperatures above 45*. This often occurs as much as 4-6 weeks ahead of plants in the landscape, so you can be close to 100% certain of killing cold temperatures if you move the plants outdoors now.

Additionally, we often use the 1 or 2 zone rule of thumb differential in hardiness for plants in containers (I noted JAG's 2-3 zones for extra safety) but we need to consider that plant roots in soil are rarely subjected to temperatures much below 25* (because of the moderating effect of geo heat).

It's wise to remember that root death in woody material isn't instantaneous, and doesn't occur at one particular temperature. Roots succumb to cold over a range of chill with cultural conditions affecting the process. The finest rootage will die (freeze) first, and the slightly thicker and more lignified roots will follow as temperatures fall. The last of the roots to succumb to cold injury will be the more perennial, lignified and thickest roots.

Since any root death is a setback from an energy allocation perspective, and root regeneration takes valuable time, it's probably best to keep actual root temperatures in the 25-45* range as long as we possibly can while the plant is resting, even though the organism as a whole could tolerate much lower temperatures. Even well established shrubs become very much like cuttings if all but the roots essential to keeping the tree viable are lost to cold. Regeneration of roots is an expensive energy outlay and causes the plants to leaf out later than they normally would and shortens the natural growth period.

We already know we need to keep the emerging flush of foliage protected from frost, and if we want to protect the fine roots, we want to keep actual temperatures higher than the low 20s. I over-winter some 150 trees in the garage, about half of which are deciduous. After they begin leafing out, I load them on a large wagon and move them outdoors in the AM on days when temperatures allow, and keep them in the garage in front of a window (as noted above in JAGs post, light is key, especially when you are dealing with ornamental material) when frosty temps threaten. This strategy is extra work, but it keeps the finest rootage viable & protects the foliage.

Alternately: If you act before budswell indicates a decrease in the plants' cold tolerance, you could bury the entire container in a garden or bed, which would retard the spring flush & ease worry about root issues & early leaf-out.

Al

Here's the problem with over-wintering our deciduous containerized material in buildings: They ALWAYS leaf out too early, and this is a clear disadvantage. The reason for the disadvantage is that buds respond to rising sap, stimulated by a few days of soil temperatures above 45*. This often occurs as much as 4-6 weeks ahead of plants in the landscape, so you can be close to 100% certain of killing cold temperatures if you move the plants outdoors now.

That's a really good point, Al. Plants kept in a building for winter protection are going to need to be protected from the cold extremes that may still strike once the sheltered plants begin swelling up their buds.

Going back a year to the OP, AllisonW, if you are still around, how did your Top Hat blueberries fare for you? I confess I have tried TopHat in my zone 5 Wisconsin and failed. I believe the failure is mostly caused by using young plants in the middle of summer rather than spring planting more mature plants, but I am curious to know how others have fared with this variety in containers in the colder zones.

Well I just got one of these in the mail and thank goodness for this thread. Little thing, was in the shipping container for about 4-5 days. I watered it and it is sitting by the window right now. I will plant it tonight in the biggest plasticpot I have, gotta be about 4 gallons, using the Miracle Grow Moisture control soil.

I am reading that they like azalea food? Is that true? I have another variety in the ground in my yard, and there are loads of wild blues surrounding me. Should I try this stuff on them?

I too really would like to know how overwintering went. I am thinking about putting it either in my cold garage, keeping it moist, watching for leaves, or putting the pot over my septic discharge tank, which is always a bit warmer than the rest of the yard in midwinter from household water usage, maybe wrapped in something or piled up with leaves too.

Any advice on what to do when I plant toight would be awesome!

I would caution you strongly against putting the 'little thing' in a 4 gallon pot with MG moisture control soil. It's extremely probably that's a recipe for failure or at least greatly diminished vitality while the plant struggles to colonize all that wet soil with roots. Why not start it in a gallon or half gallon container and move it up in container size when it's appropriate?

You can very effectively over-winter the plant by burying the container in the garden or bed at season's end and mulching - on the north side of a building, close to the foundation is great. It's better than over-wintering in the garage. Some sort of protection against rodents would be nice, too.

Try to use a fertilizer with ammonium sulfate (21 percent N), and please do not apply nitrate forms of N, such as calcium nitrate, or fertilizers containing chloride.

Al

Do the blueberry bushes need acidic fertilizer up to winter? And how often do you have to put it on through the year? Thanks in antisapation of an answewr..............Dee

How often you fertilize depends on several things, and there is no single answer. How strong the solution is, your watering habits, how fast the soil is (drains), temperature and how robustly the plant is growing all enter into the decision.

If the plant is growing well, and you're using a soluble fertilizer - try every third watering at 1/4 strength, every two weeks at half strength, or monthly at full strength. The low strength solutions at more frequent intervals are better. Blueberries are sort of unusual in that they thrive in soils where the pH is between 4.0 - 5.0. One of the main reasons for thios is the lack of efficiency with which blueberries take up Fe (iron). Acidic conditions are required to increase the quantity of Fe available in the soil solution. In addition, low pH ensures that N is able to exist in the form of NH4+ (ammonium) which is more readily utilized by blueberries than other N sources, such as NO3- (nitrate).

As mean temps drop below 50*, the demand for nutrients drops dramatically. If they were my plants, I would probably have supplied a weak dose of MG 30-10-10, or 24-8-16, along with some 0-0-3 ProTeKt around Sep 1 and again Oct 1, then called it good until spring.

Al

Thankyou very much tapla I just put 1/2 cup of holly tone around each of the bushes and I won't do nothing more till spring but I just wondered if I was supposed to be giving some acidic fertilizer all growing season? Thank's again Dee

Yikes - are they in containers? That's a lot of fertilizer ...

Al

No they are in the ground I will keep you posted on how they do If I added too much will I kill them?

You're prolly ok, seeing as how they're in the ground. You should prolly have mentioned that, since you're on the Container Forum. ;o)

Yes, too much fertilizer can harm/kill plants by making it impossible for them to take up water, or in some cases, actually reverse osmotic flow & PULL water from the plant's cells. The results of this condition are called fertilizer burn or plasmolysis.

Al

Thanks to all of you for the info on the Tophat. I have my first one - got it through the mail last spring. It did nothing all summer, probably because I need another one. And also, I was going to leave it in my garage all winter - I live in Minnesota where it can't stay outside in a pot. My garage stays around 30 degrees when it's coldest outside. It should be ok, right? Another question, it's starting to turn red, but it has little red dots all over the still green leaves. Is it ok? I had a lot of thrips this summer in my gerbera daisies and my tomatoes got a virus from them. Could they have transmitted something to the blueberry bush as well?

Tracy

A disease called red ringspot causes red spots on the upper surfaces of leaves, and powdery mildew causes red spots in blueberries on both the upper and lower surfaces. Perhaps you could search for photos of the diseases & see if they match your symptoms.

Al

I hope it's mildew. Because I think ringspot can't be fixed. filix

Just wanted to add this finding. tschulties if you are still watching this thread I had some red spots on my blueberry leaves. I sent some samples to my local cooperative extension. They came back as leave rust fungus "naohidemyces vaccinii" It is wind borne urediniospores from hemlock trees. Its not usualy a problem. I would send some leaves to your c extension. filx.

I plan to create a "pen" to over winter my three bushes. I have a wooden fence on the East side of my home (no suitable North site) and will use chicken wire, place the pots inside and cover/fill with leaves. I'll add leaves as they compact so the pots are covered by about 6" or so. Should I cover the branches as well? Will the snow that accumulates on top be sufficient for water needs? Should I place a funnel through the top leaves to the pots so I can manually water. What frequency should that be and how much?

I'd like to hear other strategies, successes and failures. I wonder if Lilacs could be container grown, given a large enough pot was used for the variety. Hmmmmmmm.

Geoff

You'd better plan on keeping the leaves dry or you'll develop fungal issues that could kill the plant. You will need to develop some kind if irrigation strategy or bury the containers, in which case you probably needn't worry about it.

Wouldn't an unheated garage & a shovel of snow every month or so be easier?

Al

Al, sorry for being dense, but do I understand correctly from your previous posts that overwintering blueberries in an unheated garage with a bit of watering over the winter is better than bringing them inside? (Burying them is not an option for me.) Thanks so much!

Dan

If you mean inside the house, the answer is a resounding YES. ;o)

Al

Ok, I give up. I need help. I live in Zone 5 (Chicago) and have a problem. I purchased my second set of Top Hat blueberries (2) and (1) Northsky. The 2 Tophats are in a box on my patio. The problem is that the box is 6' x 2' and weighs over 400 lbs. It cannot be moved to the northside of the house without a forklift. The Northsky is in a very large container but it also cannot be moved because of the weight. I had the same 3 plants last winter and for some strange reason none of them even had 1 leaf sprout this spring. They had plenty of snow on top for water so I don't know what happened. Could it have been because of the sun? The cold? Anyway how can I protect them this year so this does not happen again? I love blueberries.

They probably froze. You should be thinking of a strategy to keep the soil warmer. Containers above ground or only resting on the ground lose out on a considerable amount of geothermal heat, which is why you can't even always rely on plants normally hardy to zone 4 being hardy in containers in your zone.

Dig them & pot them up after dormant & overwinter in an unheated garage, or dig them & bury them in the soil for the winter & then repot. Otherwise, find a way to warm the soil when temperatures are below 20*.

Al

Thanks tapla. I still have a problem. I don't have a garage or a north side of the house to put them. This year I possibly can bury them but next year I will be putting in raised beds and won't be able too. Is it possible to repot them and put them in the crawlspace under my house? It is unheated but has a window for light (should it have light?). It might be just as cold as outside but it is protected from the wind. Would it work if I put burlap around the pots? Also, if I bury them outside should I cover them with anything to keep the branches from freezing? It seemed to me that last years plants had this happen to them. Thanks again

Crawl space will be too warm. No need for light, unless they're too warm & growing. Wrapping pot with insulation would help marginally, but only if they are on the ground (a heat source the insulation could help retain). In winter, the upper part of the plant is much hardier than roots. Be right with the roots & you'll be fine.

Al

Hi everyone. Happy Spring. Here I go again with another question. OK, I am happy to say, at least I think so, that my tophat blueberries survived their first winter even in that gigantic box on my patio. I put styrofoam cones over them with a ton of mulch and I took a peek and they have very green stems and green buds on them. It is still pretty cold here, anywhere between 28-60 on any given day. Do I take those cones off now of wait until the temperature warms more?

I just bought three dwarf tophat blueberry bushes. How do I take care of them for spring and summer.

There are lots & lots of informative threads on this forum related to blueberry care in containers. A search will reveal most of them for your perusal. Be sure to come back if you still have specific questions.

Al

Tapla suggest "Try to use a fertilizer with ammonium sulfate (21 percent N), and please do not apply nitrate forms of N, such as calcium nitrate, or fertilizers containing chloride." That's silliness perpetrated by the "organics" community. Feel free to use them.

Paul,
perhaps you missed this part?

"Blueberries are sort of unusual in that they thrive in soils where the pH is between 4.0 - 5.0.
One of the main reasons for this is the lack of efficiency with which blueberries take up Fe (iron).
Acidic conditions are required to increase the quantity of Fe available in the soil solution.

In addition, low pH ensures that N is able to exist in the form of NH4+ (ammonium)
which is more readily utilized by blueberries than other N sources, such as NO3- (nitrate)."


Josh

I have 3 top hat blueberry bushes. These are the first for me. I let them out for two to three frosts then I brought them in and put upstairs for the winter. The coolest place in the house. I didn't cut them back just watered once in a while. Went up stairs yesterday and they have blossoms on them. What do I do. Won't they be all backwards for spring. Should I cut them all off and let them rest and put outside when it isn't freezing or what should you suggest. Help
Ellen Doty

Thanks, Josh. If Paul Douglas knew me, he would know that I have no moors to an all organic ideology, that I'm driven my efficacy and results, rather than dogma. My offering can be confirmed with only a little effort/research.

Ellen - This is a hard call to make, but I think I would move them to a garage or shed and keep them as cold as you can but protect them from freezing. You may (probably will) lose the new succulent growth. We can talk more about the best course if you wish.

I won't dwell on this like I'm scolding you, but the best thing would have been to leave them go through the winter in a cold place. If you're zone 6 (can't tell by your user info) they could have stayed outdoors with no protection other than a windbreak to help prevent dessication.

Al

I am from Kamiah, Idaho. I beleive that is 6. Should I cut them back. I will put them in our shop because we have had single digit temps. How cold can they take without protection. Thanks Ellen

We're in kind of a gray area, Ellen. Your plant should be hardy there w/o protection if it slides into a normal dormancy, but temperature can trump the primary trigger for dormancy, which is lengthening of the dark period. The question in my mind is, will the plant go dormant if you expose it to cold but not freezing temperatures for a week or two, then put it outside, or has the onset of growth eliminated the plant's ability to withstand freezing temperatures.

I tried to reach a friend who is the president of the MI Nurserymen's Assn, but couldn't get him. I did call another nursery and asked to speak with someone about a technical issue regarding plant physiology. She sounded sure of herself, but wasn't convincing, even though what we decided as best was what I suggested in my preceding post - keep it as cold as possible but don't let it freeze - safe side advice.

I spend quite a bit of time working with the folks at a local botanic garden, but I'm not sure that the expertise of the arborist or horticulturists covers something like this, but I'll let you know if I come up with something more definitive.

Al

Ellen - I had a nice long visit with horticulturist Chuck Martin from Dow Gardens (they're bored this time of year) and he concurred that the best advice is to keep it as cold as you can w/o allowing it to freeze.

You might consider moving it to the garage, where if there is likelihood of freezing temperatures, you can simply cover the plant(s) with an overturned box. This will trap geothermal heat rising through the floor and prevent freezing down to single digit ambient temperatures, though I wouldn't suggest you leave the garage door open over night when it's 5*, box or no box. ;o)

Best luck - wish you well!

Next year just set them against the north side of a heated building & mulch a little - or bury the pots in the garden until spring. Your only obligation then, would be to ensure they don't go completely dry.

Al

Wonderful information! Question: I am going to give container blueberries a try this summer. Zone 6, NE Ohio. First, Al, can I use gritty mix? Second: I have a raised bed on the northwest side of my house. Could I bury the containers in the bed for the winter?

As an aside, I transplanted a hibiscus tree into your gritty mix last spring and it is so happy! I love that stuff.

Al, I've read more of the forum and now realize you would suggest the gritty mix for the BB's. I still would like to know what you think about putting the pots in the SFG over winter. The garden is very close to our heated all season patio, so there is heat from the house and there is a building about 30' to the west which is a protectant. Thanks!