Sky: Do think you should wait until plants are growing before applying fert. Then fert whenever the plants aren't growing enought to suit you. No one can tell you when to fert because there are so many variables. You must rely on what the plants are telling you. In my limited experience growing bb in pots, have found that more growth translates directly into more fruit. Just don't apply too much fert at one time and you won't hurt the plants. A small amount frequently whenever you want more growth would sum up my advice.

The Fruitnut

sydsky:

Blueberries need fertilizer when they are in a phase of active growth, or are forming berries. For my outdoor berries, I fertilize (and also apply iron sulphate) just as they are budding out, and again about 6 weeks later when the berries are forming. I don't think it is necessary to fertilize them at any other time of the year, and certainly not on a regular monthly schedule. Of course, this is assuming fairly good pre-plant soil preparation has been done, and there is compost and/or peat moss in the soil to provide small amounts of regular nutrients.

Azalea fertilizer is fine, since it is for acid-loving plants, but pure ammonium sulphate is better, and a small handful of iron sulphate should be applied together with the a.m. Just apply the chemicals in a circle around the plants, then scratch into the soil with a hand tool.

Use of "balanced" fertilizers such as 10-10-10 is not a good idea at all, since nearly all of these blends derive their nitrogen from nitrates, which make blueberries very unhappy. The nitrogen for blueberries is derived from sulphates. You can actually kill a blueberry plant with excessive applications of nitrate-based fertilizers.

Don Yellman, Great Falls, VA

Good advice. Thanks for the input. Knowing what my plants need is my new knowledge base that I need to work on.

I have an old blueberry that desperately needs a pollinator (keep getting like 10 berries from this little bush). But, it's been surviving for 7 years at least! All I do is throw some peat moss over it every year when I think of it. I also use some miracid once a year, and that's it. I wouldn't fertilize anything the first year.

Your posting is a year old, so it would be interesting to here how your blueberry plants did their first year. We have a young U-Pick near Montgomery AL and grow a variety of blueberries and blackberries. Here are some additional thoughts for you as they enter their second year of growth.

1. Don Yellman was right on track with his suggestions. Don't use nitrate based fertilizers as the salt in the nitrates will burn the roots. We feed our blueberries 3 times a year. First, when the buds start to swell with a 16-4-8 combination. Then during blossoming (about a month later) we add some ammonium sulfate followed up by a tablespoon of magnesium sulfate two weeks later to give the vegetative growth an extra kick. Then, after harvest to give the plant a good start into the summer and fall development of the buds for next season, we give them a final shot of 16-4-8.

2. If possible, maintain your soil PH somewhere between 4.8 and 5.3 as they love acidic soil.

3. For best results, plant multiple rabbiteye varities and make sure you plant the early blossoming ones with other earlies and later varieties with other later varieties. On our farm we have 5 varieties with the climax, premier and brightwell planted together and the later blooming tifblue and powderblue varieties planted together.

4. Here's a great link to diagnose growing issues:

http://www.hort.cornell.edu/department/faculty/pritts/BerryDoc/blueberry/BBparts.htm

As far as blackberries go if you're still interested let me know and I'll tell you what I know.

Hope this helps,

Ken Barber
Millbrook AL

Would the following work, as well (in a 1/2 peat, 1/2 fairly fertile red clay)?

1) Yearly applications of 2 cups of cottenseed meal per plant;
2) Yearly renewal of pine needles and composted sawdust mulch; and
3) Yearly dose of iron sulphate.

I just planted my blueberries a year ago, so I can't comment on the effectiveness.

Thanks.

From what I've read, one reason the PH needs to be between 4.8 and 5.3 is because iron present in the soil doesn't move as readily when the PH is higher than that and the blueberries definitely need their iron. So to simply add iron sulfate as a general rule may or may not be a good thing, depending on your soil test and PH results. In my case when some of the leaves on a few of my plants started to display a yellow tint with the veins remaining green, I added a tablespoon of iron chelate around each plant and after a couple of weeks the leaves started to look better. In this case their PH was up around 5.4-5.5, so it made sense to add a little iron (plus a little sulfer to get the PH back down). But, there are also other reasons why leaves may turn yellow. That's why I like Cornell's diagnostic website I listed above which provides pictures of a wide variety of symptomatic conditions to include iron deficiency symptoms. But, if adding iron sulfate as a general rule works for you than it's a good thing.

Hope this helps,

Ken Barber
Millbrook AL

Just to confuse you I have to point out that all fertilizers become nitrate as they break down in the soil. An excess of any quick release N can damage any plant as most gardeners have at some point discovered from unfortunate experience. What makes blueberries more susceptible is their shallow rootsystems which also makes them particularly vulnerable to drought.

I believe that the primary reason ureah based fertilizers are often recommended for blueberries is because of their acidifying affect. I prefer to use Osmocote for my clients due to research I have read. My own plants recieve some of my own diluted urine in early fall or early spring which certainly does no harm as my yeilds are huge and berries large and sweet. I keep them well mulched with aged wood chips.

I have often seen very healthy and productive blueberry plants in soils with a pH above 6, by the way, contrary to the literature. These soils also had a very high level of organic matter which may have increased access to iron.

Hey, Harvestman! I'd be very interesting in knowing a little more about this. . . . .

"I have often seen very healthy and productive blueberry plants in soils with a pH above 6, by the way, contrary to the literature. These soils also had a very high level of organic matter which may have increased access to iron."

What, if anything, was being done to the soils for these plants to keep the organic matter high?

dave

Dave, most commonly blueberries are installed with a lot of well mixed peatmoss which has a reputation for being acidifying but once it breaks down, not so much.

After the installation an annual application of wood chips, preferably soft wood but whatever is available will insure a rich black soil over time (even if it's just on top). 2 or 3" is enough and at least 6 months of aging a plus.

I was just reading the NAFEX list and another knowledgable grower stated the same about blueberries thriving in a relatively high pH.

I think I've decided to mulch with pine shavings. I've only got a couple plants, so I'm kinda thinking that a big bag of pine shavings from a pet store will suit me for quite a while. I've got some peat in my soil from when I planted, but I'm sure my P.H. is about as neutral as it gets. I'm pretty excited about all of this, even tho I don't like blueberries. Ha Ha, the things we do for our moms. Wish me luck. Thanks again? NAFEX list? I'll have to google that.

Thanks again.

dave

A strange thought, but would cat-urine soaked kitty litter be good because of its' high ammonia content--not a lot but just scattered when I clean box? My berries are blooming and soil is 6.0 pH.

Cat urine might be fine, but you don't want cat feces near your blueberries. The litter sounds like a bad idea.

Bethesue,

It would be about PH 7 so would not be great. I don't think the clay would be very good either and it could mat together. You could try it but I don't really see the up side to it.

Okay, thanks so much. My ph is 6, but nitrogen is very low. Getting some ammonium sulfate today. Any other compounds? Hardware store had Mag sulfate and some other sulfate they said folks use for blueberries. Thanks!

I meant to ask, folks keep saying to use Epson salt, but they don't know why--I know it has mag, but what else?

Epsom salt is magnesium sulfate, so it provides a source of both magnesium and sulfur. Beyond that, I don't know of any special qualities that it possesses. If your soil is deficient in magnesium and you don't want to raise the pH (which dolomitic lime, a common source of magnesium, would do), then epsom salt might be worth considering.

Based on this thread, I think my berries (in pots) would benefit from aluminum sulfate. I have a bag that is about 10 years old. Does anyone know if this could still be good or does this chemical change over time? Thanks.

treehugger,
I'd skip the Aluminum Sulfate,not because of its age,but from what I've read,the Aluminum could have an adverse effect on the Blueberry.
Is the pH too high in the pots?Other things like Sulfur or some kind of acid could be put in the irrigation water.
Hydrangeas like Aluminum Sulfate though. Brady