North American Fruit Explorers mailing list at ibiblio

[<dmnorton@royaloakfarmorchard.com>]

Hello John!

 

Let me see if i can shed some light on your issue.  Depending on what zone you are in (we are in zone 5), apple trees typically bloom in May.  The tree phenology for our particular zone is:

 

April 14 - 1st Green

April 21 - 1/4" Green

April 23 - 1/2" Green

April 27 - Tight Cluster

May 1 - Open Cluster

May 8 - Pink

May 10 - King Bloom

May 12 - Full Bloom

May 18 - Petal Fall

May 24 - Fruit Set

May 31 - 1st Cover

June 14 - 2nd Cover

June 28 - 3rd Cover

July 11 - 4th Cover

July 25 - 5th Cover

August  8 - 6th Cover

August 22 - 7th Cover

September 5 - 8th Cover

September 9th - 9th Cover (Terminal buds should be set by this time or earlier)

 

Buds on fruit trees usually have about seven leaves and initial shoot elongation in the spring results from cell expansion. During late June and July some of the shoot apices will flatten out and develop into flower buds. Flower buds are actually modified shoots and the various flower tissues (petals, stigmas, anthers, etc.) are actually modified leaves. Although the process of switching from vegetative to reproductive buds is not fully understood, hormones that can be influenced by environmental factors, stresses, and plant nutrition control the process.

There are several things we can do to influence whether or not a bud becomes a flower bud or remains vegetative. In general, factors that favor rapid growth, such as high nitrogen levels in the shoot tissues, inhibit the development of flower buds. Applying growth-promoting plant growth regulators such as gibberellins* usually inhibits flower-bud induction, whereas ethylene may promote flower-bud development. Mild stresses such as shoot bending and water stress may also promote flower-bud development.

(*Gibberellins are a class of related plant hormones that stimulate growth in the stem and leaves, trigger the germination of the seed and breaking of bud dormancy, and stimulate fruit development with auxin.)

Producing annual crops of high-quality fruit requires a balance between reproductive and vegetative growth. Techniques, including pruning, branch bending, and plant growth-regulator sprays, can be used to manipulate tree growth and flowering. Often these techniques affect bud dormancy, so knowledge of buds and bud dormancy is essential if we are to understand how pruning influences tree growth. It is also important to be able to identify the different types of buds on a tree, especially to distinguish between flower and vegetative buds.

Several types of buds commonly develop on fruit trees. Vegetative buds only develop into leafy vegetative shoots. Flower buds produce only flowers. Stone fruit trees (peach, nectarine, apricot, plum, and cherry) produce vegetative buds and flower buds. Apple and pear trees produce vegetative and mixed buds. Both leafy shoots and flowers emerge from mixed buds. So it is essential to have a knowledge of buds in order to know how your pruning will influence the tree's growth.

For a good overview of the process, visit http://tfpg.cas.psu.edu/129.htm and view the Apple Tree Pruning Slide Show .  

On your trees I think you can accomplish your goal by using thinning cuts instead of heading cuts.    A thinning cut is the removal of an entire shoot, limb, or branch at its point of origin. In an orchard this can include the removal of a primary or secondary scaffold limb, removal of a spur system, or desuckering interior water sprouts arising from horizontal limbs.  We are actually going through this process now in our orchard.  We have some M7 trees that are 15' tall and we want to get them back to around 10'.  We are using thinning cuts to remove 1-3 primary or secondary scaffold limbs (picking a primary 1st) per tree and then water sprouts, but not always to 2 year old wood.  Thinning back to older wood does not produce the vegetative growth that heading back does. We are then starting a new central leader at the goal height with a heading cut. 

We have developed a saying here at Royal Oak Farm when we are pruning: "When in doubt....thin out!" 

I hope this has been helpful and not created more questions!    

 

Dennis Norton
Royal Oak Farm Orchard
http://www.royaloakfarmorchard.com
http://www.theorchardkeeper.blogspot.com
http://www.revivalhymn.com

----- Original Message -----

From: John Barbowski

To: dmnorton@royaloakfarmorchard.com

Sent: Tuesday, March 20, 2007 11:41 AM

Subject: Re: [NAFEX] apple pruning question

Hello Dennis,

 

I read your email and am a little confused. I could be my lack of knowledge on fruiting spurs; perhaps you can enlighten me. I was led to believe that apple blossoms usually form in late summer. Is this process the same with spur type apples?

 

I am refering to the following statement you made:

"Heading back in older wood  results in the conversion of potentially fruitful spurs to vigorous, non-fruitful vegetative shoots ." 
 

Would this still be the result if the blossom buds have already been formed?

 

My enigma is 3 foot leaders on four of my young trees. I want to head them back; a couple of trees into 2 yr wood. This will bring the height from 11-12 feet to around 8 feet, the desired height. I don't want vegetative growth. I want to maximize production at the expense of vegetative growth.

 

I have seen a couple of pics of headers left intact on the tree but tied over such that they were inverted. The stated intent was to allow for auxin development from the leader to inhibit strong vegetative growth. Do you have any comment on this process?

 

Regards

 

John B