Nitty Gritty – How to Prune

Pruning is both science and art. Last week we looked at the why, when, and what of pruning. Now, let’s get into the nitty gritty – how to prune. Here are some thoughts that can help guide your cutting.

 

Immediately Remove:

  • Anything diseased or damaged.
  • Adventitious growth. Look like suckers but are coming from an area that was improperly cut or damaged in a previous pruning session or storm.
  • Limbs that are criss-crossing or growing towards the center of the plant. The goal is for limbs to go OUT and AWAY from the center so the foliage can get more light for photosynthesis.
  • Suckers. These are shoots that come up from the base of the plant, trying to be new leaders (primary limbs). 

Suckers at the base of a shrub There's a sucker born every minute (PT Barnum)
All of these tiny shoots coming up near the base of the plant are suckers. PT Barnum would welcome them, but he’s no gardener.

 

Determine Desired Height

How tall do you want this to be once you’re done pruning? Choose a height to guide your cuts (ex. I aim for waist- or chest-high for shrubs since that’s easy to approximate). 

 

Shaping 

Look for little buds (AKA lateral meristem/axillary bud) on the limb in question. They might be clearly visible on a naked branch or they might be hidden right where a leaf attaches to the limb. The way these nodes are pointing indicates which way the plant could grow if you chopped right above that point. (Obviously if you chop below, the bud would be gone and couldn’t direct the growth).

Fun with Biology:

A meristem is a plant’s version of stem cells. Stem cells can differentiate into any type of cell that’s needed (sort of like our bone marrow and umbilical cord blood). An apical meristem is just plant stem cell tissue found at the apex, or top, of the plant. 

Lateral meristems are stem cells found near a bud or side shoot

Plant hormones from the apical meristem called auxins send chemical signals to the lateral meristems that inhibit lateral growth. Cytokinins (another plant hormone) allow for some lateral growth. For more on this, check out this cool article

Here’s the REALLY cool part: if you chop off the apical meristem (AKA  pruning), auxins can’t be delivered and whatever lateral meristem is closest to the top becomes the new apical meristem through cell differentiation. It’s crazy-amazing! Check it out:

Apical meristem is at the top of the limb, lateral meristems/buds are on the sides of the limb. Each bud shows the direction a new limb could grow if the top of the limb were pruned.Cutting above a lateral meristem/bud will turn that bud into the new apical meristem and the limb will grow in the direction of that bud.Here's what the new limb would look like if pruned (new growth going in the direction of the new bud with foliage at each lateral meristem/axillary bud.

 

Science and pruning are so cool!

 

Here’s an example of my pruning before & after, using the tips above. Subtle, but effective!

Shrub after pruning

 

Tree Limbs: 3-Cut Method

Growing a Greener World, one of my favorite gardening shows, has a great episode on pruning. I recommend watching the entire episode. If you just need to know how to best remove a tree limb, check this out:

 

A Note About Tree-Topping/Crape Murder

Ugh. I hate this so much. I hate that I have to tell people this AND I hate that tree service companies actually suggest this to their customers. Trees SHOULD NOT have their canopies removed. It’s atrociously ugly and it is usually fatal to the tree. At the very minimum it’s extremely damaging (to the tree’s health and to your property when the tree eventually fails and falls on something). Crape Myrtles are frequent victims of this treatment, hence the term “Crape Murder”. If a tree is overgrown, here are your best options:

  • Remove an entire limb from where it joins up with the trunk or a large branch using the 3-cut method
  • Cut down the entire tree – it will look better than topping AND prevent you from having a huge insurance claim after it falls down on your or your neighbor’s property
    • Bonus: this frees up space to plant something better (more appropriate size or native species)

A tree that's had it's canopy removed improperly using a topping method.

An improperly pruned tree. Tree topping is murder!

Results of tree topping - scraggly limbs, knots, and decay

For the love of Pete, don’t do this!!!! See how sickly the new growth is? The knots? The decay? It’s awful!

 

Additional Resources

Here are a few other resources if you have more questions about how to prune:

Now you know the why, what, when, and how of pruning! It’s not that hard once you understand the biology going on behind the scenes. 

I’d love to hear your stories about pruning (horror or otherwise)! Did you inadvertently kill a plant by pruning at the wrong time (guilty here!)? Have a bumper crop of flowers or fruits after a hard prune? What did you do with the harvest? Let me know in the comments!

Coming up:

Sunday: Good Soil

Next Wednesday: Square Foot Gardening Techniques

 

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