Showing posts with label grafting. Show all posts
Showing posts with label grafting. Show all posts

Thursday, 21 June 2012

Grapevine grafting (part 2): Callusing and rooting.

   After the grafting process is done, the cuttings go through a process called callusing.  A callus is a tissue growth produced by the plant where it has been injured.  In our case, there is an injury at the graft union (on the rootstock and the scion), and at the bottom end of the rootstock.  Callusing is an essential part of bench grafting.  No callus, no graft or roots.  When the plant sustains an injury, it produces this growth of undifferentiated cells (callus) to heal itself.  These cells are called undifferentiated because they can transform into any part of the plant (roots, stem, bark, etc.).  For the graft union specifically, it will act as a weld between the two parts (rootstock and scion) that will eventually become lignified into one piece.  At the bottom end of the rootstock, these cells will become roots.
Nifty little creatures aren't they?

It will go from this...
   There are a few things plants need to produce callus.  When performing the graft, the plant material in dormant.  The first thing to do is to shock them out of dormancy by giving them heat and humidity.  The ideal temperature for vines to produce callus is around 27 to 29 Celsius (~80 to 85 F).
At these temperatures, a vine cutting can produce callus in as little as a week, but it typically takes two to three weeks.  For ideal humidity, I like to put the cuttings in a sealed plastic bag filled with very moist (but not wet) peat moss.  I found that for optimal results, the humidity level has to be just right.  I simply add water to the peat until it just starts releasing water when squeezed tightly into a ball.
... to this!
  And mix it very well so it is evenly damp throughout the bag.  Then put cuttings in and seal.
     The next step is to keep those cuttings warm and moist for the next two weeks.  There are many ways to do this.  Nurseries use ''sweat boxes'' which are more like heated insulated rooms with shelves where they store their plants.  I built a miniature version of this with the smallest space heater I could find, and the biggest Rubbermaid container  could find (make sure that the heater has a thermostat control!!).  I  put the space heater inside the container, set it to 85F, and voila!  Of course, there could be many variations of this.  The goal is to keep the cuttings at that optimal temperature the whole time with as little variation as possible.

   After 2-3 weeks, you should have abundant callus growth and even roots already started.  Next, dip the top of the graft (tape and all) in the melted wax making sure to cover the graft union completely and dip in cold water right after to cool down. I use a ''bain marie'' to heat up the wax.  Don't let the wood in the hot wax too long or it will damage the buds. This wax will seal the graft and keep it hydrated while the wound heals and until the plant can hydrate itself. The residual wax layer will eventually fall off on it's own.  You may notice that some of the buds will have started growing and some will even be up to 2-3 inches long (they will be white due to lack of light). They are very fragile at this point so handle them carefully, they also need to be dipped in the wax because they would just dehydrate and die.  If for some reason one breaks or dies, a secondary bud will usually start growing to take its place. Although this will take a lot more energy out of the plant, the cuttings usually survive and once a root system develops, they will quickly recover.

Indoor garden with baby vines.
   Its now time to pot these cuttings and gradually introduce them to the light.  Gradually is the key word here.  Put them outside in the sun and they will surely die from shock, and the week shoots and leaves would burn.  I like to use an indoor garden light with a high pressure sodium bulb.  They can be bought at any hydroponics store.  Fluorescent fixtures, although less intense, can also work and , of course, a sunny window will do the trick if you only have a few plants.  I like the high pressure sodium light because it is the most intense of them all (but not scorching like the sun...).  With that setup, I find I can have the best control over the growing conditions.  As you can see on the picture,  make my own pots using vinyl ''downspout'' used for the fabrication of eaves through.  I like using this material because I can make my pots high enough to bury most of the stems of my cuttings.  Regular pot are either not high enough, or to wide, and not space efficient.  Another advantage is that they are square so there is no loss of space between pots.  So I cut them to length and then use screen material (used to repair window screens) secured with duct tape to close the bottoms.  All of this can be found at any hardware/home reno store and is rather inexpensive.

  The plants will start growing more and more vigorously as the produce more roots.  After a few weeks, they will look like this...
Another chip bud (sill wrapped).
You can see the callus through the tape.
Chip bud with callus growth.


Happy vines ready for the outdoors!
 Once the plants look healthy, I start taking them outside in a shaded area for a few hours a day.  And this is very important, they are not ready for full sun yet.  Remember, even in the shade, they are now exposed to more light then any artificial lighting can produce.  I usually take them inside for the night though.  These plants were started in mid March and we are now close to the end of April/early May and the nights can still be too cold.     After a few weeks outside, the plants are gradually exposed to direct sunlight and are now hardened.

They can't have enough sun now!
Graft union. Almost healed...


The vines are now ready to be transplanted.  They can be put in their permanent spot right away if late enough in the season.  Frost could be devastating at this stage (well... at any stage really!)  I chose to put them in larger pots (1 gal. pots) because my planting site was not ready yet. 

Nice roots at the bottom...
Grafted Riesling vine after a few weeks outside.

Grafted Chardonnay.
Ready for their new home!

Thanks for visiting!
Come again!

Friday, 15 June 2012

Grapevine grafting (part 1): The graft.

    There are many reasons to graft grapevines.  The main reason, and why grafting vines became common practice, is disease.  To make a long story short, in the mid 8000's, when the vineyards of Europe got infested with phylloxera ( a louse that was unknowingly introduced from contaminated vines that were imported from... America), it was quickly discovered that vines native to America seemed immune to the disease.  So they had two options.  Breeding or grafting. 
      Introducing disease resistance in the European vines by breeding them with American vines was tried and partially succeeded.  I say partially because although the hybrid vines were resistant, they lacked some of the winemaking qualities the original vines had.   One of the side effects of introducing American genes in these hybrids is that the resulting varieties were a lot more cold hardy, enabling us Canadians to grow vines where most European (vinifera) vines would quickly die due to our cold winters.  Most of the modern cold hardy grape breeding programs (University of Minnesota, and Cornell in NY) use these old ''french hybrids'' as a starting point to create new varieties.  There is a lot to say about breeding and hybrids so I will leave the rest for a future post.
     The other option, and the one they quickly chose, was grafting.  By grafting a European shoot (scion) onto an American vine (rootstock), they got the best of both worlds.  The root system of the rootstock was completely immune to phylloxera, and the above ground portion of the vine produced the grapes the winemakers liked.  Most vinifera varieties (Chardonnay and  Merlot, to name a few) are now grown this way around the world. 
    Other interesting effects of grafting are changes in the way vines behave like earlier budding or earlier harvests.  It can also make vines more drought resistant, grow better in different soil conditions.  So there are advantages in grafting vines even though they are disease resistant (like hybrids) to a different rootstock for those reasons.

    So for my grafts,  I chose to use a wild riparia vine as a rootstock.  Those grow like weeds around my vineyard so I thought they would be good candidates. The vinifera varieties I've grafted on the rootstock are Riesling and Chardonnay. 
    And now, the procedure...

    The technique I used is called dormant bench crafting.  Both the rootstock and the scion wood are dormant at this stage.  It seems to be the most common way to graft grapevines.  I tried two variants of this method.  The first is a standard ''omega'' graft where you use a grafting tool to cut the wood into an omega shape so that the joint locks kind of like a jigsaw puzzle.  I bought one of those tools at Lee Valley's for around fifty dollars if I remember correctly.
    I also tried a technique called chip budding where you graft only a bud (chip) from the donor vine onto the rootstock.  This technique is usually used in field grafting, where a dormant bud is grafted onto an actively growing vine in the field.  I couldn't think of a reason why it wouldn't work on a dormant rootstock so I tried it.  My success rate ended up being around 80% with both methods so I figure they are both worth mentioning. 

1)  Omega Grafting.

Tools you'll need.

You will need an omega grafting tool,  painter's tape,  and wax.
You can use grafting wax if you want, I used paraffin wax from a home spa machine that my wife bought and use only once (free wax!), and it worked fine.  The tape is to help secure the graft union.

Cuttings all hydrated and ready to go.
 This is my riparia rootstock.  It was harvested in December and
 kept dormant in my fridge until grafting time.  Cuttings like these can be kept for up to a year provided they are kept moist and cold (0 to 1 Celsius).  I rap them with moist paper towels and seal them in a big Ziploc type bag removing as much air as possible.  You can use your kitchen fridge to store them but try to put them in  the back end of the fridge where it is the coldest.  If you could have a dedicated fridge to store them in,  it would be ideal.  You want to keep the temperature as steady as possible.  I bought a mini-fridge ( on sale for 80 $) which was ideal.   I just set the temperature and left the cuttings in there until I  needed them.  Before you start, weather rooting cuttings or grafting, the wood should be immersed in water for a day or so .  I just put my cuttings in the sink and put a plate on top of them to hold everything under water.  Hydrating them greatly improves the success rate.  Then, just before I start, I dip them in a diluted bleach solution (10 %) for 30 seconds, and then rinse them immediately with plenty of water.  This kills any mold/bacteria that could infect the wounds you'll make when grafting.  Make sure not to soak them in bleach for too long though because it could damage the dormant buds, and the cutting would die.

The next step is to ''debud'' the rootstock.   I used a utility knife (forgot to include in the first picture...) and simply cut the buds off.
Each node contains a bud (three buds actually).  The main bud is easy to see but there is also a secondary and a tertiary bud just under the main one.  These buds normally stay dormant but if something happens to the main bud, they will take over and start growing.  You'll want to make sure to remove them all otherwise, throughout the life of that vine, you will have to deal with removing rootstock suckers that will keep coming every year.

omega cut.
When grafting, one of the most crucial things is to match the size of the wood (rootstock and scion) as closely as possible.  For the graft to be successful, the cambium layers have to be aligned almost perfectly.  The cambium is a thin layer of the wood directly under the ''bark''.  This cambium produces the callus that will weld the graft union into one piece.  Mismatched wood will yield week grafts at best, but will most likely not take.
      Once the buds are removed from the rootstock, I make my first ''omega'' cut on the top of the cutting.  Which reminds me... Cuttings don't grow upside down.   Make sure you are holding them the right way.  The buds usually point up but if you are unsure, there is always a scar directly under each bud.  So next, I make my cut on the bottom of the scion (the grafted part).  It has to be matched to the rootstock so that the graft union ''interlocks'' as in the picture.  Remember that the scion also has an up and a down.

Graft complete.
 Snap the pieces together and wrap tightly with the tape and there it is!  The graft is complete.

    I will switch to chip budding now since it is a variant of this method and get to callusing later.

2) Chip budding.

Tools you'll need.

  Less expensive tools here.  A utility knife with a sharp blade, plumbing Teflon tape, and the same wax.  Proceed the same way as omega grafting for soaking, sterilizing and ''debuding''. 

Chip bud incision.

Instead of making a cut on the top of the rootstock, you make it on the side as in the picture.

Rootstock and chip.
   Next, the goal is to match that incision as closely as possible with the bud.  It takes a little practice to get it right but it's worth it.  Make sure to have some wood to practice with.  To make the ''chip'', I make a first cut at a diagonal starting just under the bud, and slice right through the trunk (cutting the bottom off completely).  All that's left to do is to ''peel'' the bud off with a second cut.  Again, try to match as closely as possible (see picture on the right).

Hold tightly.

Then, push the chip in the incision firmly...

Wrap with Teflon tape.


                       ...and wrap tightly with Teflon tape to secure the bud,

and done! 

p.s. I apologize for the lack of pictures.  I just noticed a lot of them were unusable (bad quality).  I will take better pictures next time and update this post. 

Click here for part 2: Callusing and Rooting

Thanks for visiting!

Wednesday, 13 June 2012

Potted vineyard... for now.

Hi all!

Seems like an eternity passed since my first post.  The past few weeks have been quite busy since my wife and I are in the process of selling our house and buying a new one.  With a lot less free time, it has been difficult to keep up with things in the vineyard (and this blog) but I figured it was time for an update anyway. 

Here are this year's newborns! 

Temporary vineyard...  waiting for a new home.
All of those were started from cuttings and most are own-rooted hybrids.  But a few varieties ( Reisling and Chardonnay) were grafted to a disease resistant rootstock.  This is my first successful attempt at grafting after having failed miserably last year.  I had ~80 % take/survival rate this year ( none of the grafts took and/or rooted last year). 

Grafted Chardonnay vine.
Grafted Reislng vine.

The rootstock I used is a wild riparia variety that grows everywhere around here and seems to thrive even in very poor locations.  The reasoning behind this was that these wild vines are so well adapted to this environment that they would be good candidates for rootstock.  I guess time will tell... 
One thing I find interesting is that, even though the plants are only a few months old, I can already see a big difference between grafted and own-rooted plants of the same variety.

Grafted Reisling vine (3 months old).
Own-rooted Reisling vine (1+ year old).

Note that the plant on the right is a second year vine started last year from a rooted Reisling cutting.  Seems like my rootstock (left picture) added tons of vigor to a normally low to medium vigor variety.  Another factor could also be that the riparia is a very early budding variety.  That would have given the grafted vine a head start since it would have started growing way before the other. 
Just the beginning...  It will be interesting to compare both vines at the end of the summer, and a year or two from now.

Wild Riparia (rootstock) vine.
Another wild Riparia clone.
I will be experimenting with rootstocks and grafting a lot more because it really seems to make a big difference in growing habits and vigor.  Even with hybrid varieties, even though they don't really need the disease resistance they could benefit from other characteristics of the rootstock like early or  delayed budding, early fruit set and harvests, shorter hardening period, etc.  These are all things you read about but that are difficult to visualize until you can actually see them growing side by side. 

Here are a few more pictures of what I have going on...

Merlot or Cabernet??
(if someone can tell, please help!)
Started from seed 3 years ago.
''Cab-erlot'' leaf.
(again, please help...)

5 year old Pinot Noir flowering.
More flowering Pinot.
Thanks for visiting! 

P.S. I will post a detailed description of my grafting method shortly.  Just sorting out the pictures...