In 2008, I wrote a blog post about my initial success growing blueberries here in Silicon Valley.

Blog: Blueberries in Sunnyvale

It’s a great post, and it covers a lot of the basics of which varieties to plant, and an example of how to set up watering properly.  I ended on this note:

If you’ve read this far, chances are you think that replacing useless ornamental shrubs and bushes with gorgeous, fruiting blueberry bushes is a dream come true.   Well, you too can live the dream.  I’m happy to announce that growing blueberries in Sunnyvale is definitely a reality.

This will now be my third season harvesting blueberries, and it looks like it will be a bumper crop this year.  However, I thought it was worth putting together an update, because the second season was not very successful at all.  In fact, it was lessons from the second year that really led me to do some research and come up with the techniques that I believe have led to a great 2010.

How to Fertilize Blueberries

I’m not a terribly creative or active gardener, in that I tend to favor plants and setups that don’t require constant maintenance.  Blueberries don’t require a lot of work, if you set them up properly, but they do require fertilization on an annual basis.  More importantly, they require the right kind of fertilization.  (Sources:  Michigan State Agriculture, Ontario Ministry of Agriculture)

Here are a couple key facts:

• Blueberries require acidic soil. Actually, according to eHow and other sites, the proper pH for Blueberries can be anything from 4.3 to 5.1.  That’s pretty acidic, and much more acidic than any soil you are going to find in the Bay Area naturally.  That means, you’ve got to add something to the soil at least annually for Blueberries to flourish.
• Traditional fertilizers can hurt Blueberries. Like most plants, Blueberries need nitrogren.  However, they don’t handle it in nitrate form well, and it can lead to significant issues.  You can use fertilizers made for acid-lovers like Azaleas.  Instead, look for sulfer-based fertilizers.

I personally use the following process:

1. I strip about 1-2 inches of accumulated leaves and top soil off the area.
2. I use ammonium sulfate (purchased at Home Depot, in the garden section).  I sprinkle liberally around the bushes, based on the package instructions.
3. I put down a few bags (about 1 inch) of new top soil from bags.  These bags contain fresh organic matter, which lightly fertilizes.
4. I mulch the entire area.

When to Fertilize Blueberries

This is the part I got wrong in 2009.

In 2009, as per some of the recommendations on blueberry.org, I waited to fertilize my blueberries until they started to flower.  This was a huge mistake.  In the end, I was left with a small number (<30) flowers per bush, and a very sparse crop.

My working hypothesis was that, due to the warm winters in Silicon Valley, the plants never really go fully dormant, but do set based on the frosty nights in December/January.  As a result, they bloom by February, as the weather warms but is still wet.  A few articles on the web from other warm weather growers seemed to confirm this theory.

As a result, this year, I decided to prepare and fertilize my blueberry bushes over Thanksgiving using the treatment I found at this tree website.  I was actually very fortunate on the timing – we had quite a bit of rain in December, as well as a few frigid nights, so I felt like I did the work “just in time”.

Results for 2010

No harvests yet, but all eight bushes (four of each variety) are literally bursting with huge (20 berry+) bunches of green blueberries.  I think there are at least 200+ berries per bush.  Barring some unforeseen tragedy, it looks like the early fertilization and preparation was key for preparing the plants to make the most of their fruiting season.

Here is a quick snapshot that I tweeted out this weekend.  You can see some of the leaves are still red from the winter, although there are quite a few new green shoots and leaves.

I hope this helps any aspiring blueberry growers out there.  It’s a real delight to pick blueberries in the morning on the way to work.