Fundamentals of Pruning

  • Do not over-prune. A rule of thumb is to not remove more than 25% of the trees total foliage in one year. With young, very healthy trees you can remove a little more, up to 35%. On older, mature trees and sick or stressed trees, less is better, under 15%.
  • All pruning cuts are wounds. Never make a cut unless you have a specific reason for doing so.
  • Pruning paints and sealers are a waste of time and money.
  • Under the name of each tree, I have included a general note that will read as (Small Size) or (Medium/Large Size), etc. These are generalities, and I have included them for ease of reference.

 

Screwbean before pruning One of my beloved Screwbean Mesquites before I pruned it. The shovel is in the photo for scale.

 

 

 

Screwbean after pruning The same Screwbean after pruning. I've reduced its size by taking off the very tall vigorous growth, all the suckers and water-sprouts, and branches that were crowding or crossing in through the middle. All together, I took off about 30% of the foliage-equivalent of wood. Best of all, it looks completely natural and un-pruned.

Temporary Branches and Heading Cuts

  • Some branches and twigs are permanent and will stay on the tree throughout its life. Other branches and twigs should be seen as temporary and will be allowed to remain until they have served their purpose, then removed.
  • Temporary branches are important for 'feeding' and strengthening the branch or trunk to which it' attached.
  • Temporary branches should be removed before they get too large, so you don't leave too large a wound where it' attached. Temporary branches can be 'slowed down' by making heading cuts.
  • Heading cuts are cuts that remove the growing tip of the branch with the cut made just outside (beyond) a bud. Buds are always present where a leaf attaches to a branch, even if you don't see one there.
  • Heading cuts should be made at a bud that is on the side of the branch where you want the new growth to be oriented. For example, if a heading cut is made just beyond a bud on the topside of a branch, the new growth that will come from the bud will grow up and out from the topside.
  • Heading cuts should only be made on young wood, usually a half inch or less in diameter.
  • Temporary branches are especially helpful in strengthening weak trunks, and shading trunks from sunburn. If trunk wood is exposed to mid-day and afternoon sun, wrap or otherwise shade the trunk for the first summer, or paint it with a white latex paint.

Cuts on Larger Wood

  • Pruning cuts on larger wood should be made one of two ways. Either the entire branch should be removed, or a cut to a lateral branch should be made.
  • When removing an entire branch, look for the branch collar and ridge. The collar is an area of swollen tissue at the point of branch attachment and usually more evident towards the bottom. The ridge is a lifting of tissue on the topside where the two branches come together and looks like a mini mountain range. The cut should be made just outside the ridge and collar, leaving both intact. This allows for the most rapid closure of wounds.

 

Sweet Acacia The branch collar is well-evident all around this branch, where it attaches to the larger branch.

 

 

 

Branch Collar Cut After the branch is removed, the branch collar is left intact. It will heal quickly.

 

 

 

Branch Collar Healed This wound is about one year old. 'Wound-wood' is growing over the wound from all sides, sealing it off. This was a well-placed cut that left the branch collar intact, and the resulting wound-wood 'donut' is well shaped and will cover the wound quickly.

 

 

Branch Collar Closed These wounds have completely closed. Stress from the wound is now greatly reduced or gone, and the live tissue is much more defensible to insects and pathogens than the dead wood it covers.





Angle of cut If no branch collar is evident, this photo shows an approximate appropriate angle of cut. The top of the cut is just outside of the branch-bark ridge and the bottom of the cut anticipates the collar position, even though the collar is not showing (the swell of wood that I always look for).



  • A cut to a lateral branch removes the main branch back to a secondary branch growing off of it. This secondary or lateral branch should be at least 1/3 the diameter of the branch being cut back. This cut should be sloped back and away from the lateral branch that is left behind, usually at about a 30 degree angle.
  • When cutting off branches that are large and have significant weight, a 3-cut method should be used. This consists of an undercut, a top-cut and the final cut. The undercut is made first, a few inches out from where the final cut will be made and about halfway through the branch. Second, a top-cut is made a few inches further out, from the top of the branch, down. This removes most of the branch (and weight) without ripping tissue beyond and into wood that will remain behind. Then the final cut is made.

3 cut - undercut The first cut in the 3-cut method 'the undercut.'

 

 

 

3 cut - topcut

The second cut in the 3-cut method 'the topcut.' This will drop most of the weight harmlessly away.

 

 

3 cut - final cut The third cut in the 3-cut method 'the final cut.'

 

 

 

3 cut - done cutting The 3-cut method removed this branch while leaving the branch collar safe and intact.

Which Branches Should be Pruned

  • Branches should radiate out on the side from which they grow. If they cross back in through the middle or rub against another branch (causing a wound), they should be removed. Give branches room to grow. If two branches are crowding each other, remove one.
  • Watch out for weak crotches! Weak crotches are attachments between two branches or a branch and the trunk, where the angle of attachment is narrow. Wider angles of attachment are better. Narrow angles (weak crotches) cause the bark to be pinched between two branches, and the bark is non-living, non-attached tissue. This prevents the two branches or branch and trunk from continuing attachment on the top-side, and when the branch gets large and has a lot of weight, it can be ripped off in a high wind, possibly causing a devastating injury

Strong crotch angle A strong crotch, and hence, strong branch attachment. The angle is wide enough, approximately 70 or more degrees where the two branches come together, and the wood is continuous and not 'pinched'.

 

 

Weak crotch angle A much weaker crotch and branch attachment. The angle is approximately 40 degrees and you can see how the wood has become 'pinched' in between the two branches. The dark stain emanating from the crotch is due to sap oozing from the stress on living tissue caused by the included or pinched wood.

  • Dead wood has no benefit for the tree and keeps wounds from closing. Remove it.
  • Suckers and water-sprouts are very upright and fast growing branches. Suckers originate from the base of the tree, water-sprouts from in the canopy. Both should be removed or headed back to a bud, and earlier is better.
  • If two branches grow from nearly the same point, one should be removed. If they are too close to one another, a weak crotch will likely occur later, as the branches grow in diameter.
  • Branches should be well-spaced around a tree, radiating out in all directions. They should also be well-spaced up and down the trunk, with 6 to 12 inches between permanent branches on small trees and 18 to 24 inches between on trees that will become large.

 

Poor branch spacing This almond tree shows poor branch spacing. There are way too many permanent limbs all attached at the same point.

 

 

Good branch spacing Further up in the canopy of an almond tree, the spacing is much better. The branches are well separated, usually by at least 1 foot, and they radiate out in all directions.

  • With palm trees, it is best to only remove dead and dying foliage. Palms recycle nutrients from their fronds (leaves), and if you cut off green fronds, you take those nutrients away. At the very least, do not remove fronds from above the 3 o'clock to 9 o'clock positions.

Tools to Use

  • Use good quality tools to prune. You get what you pay for.
  • Use by-pass hand pruners for small wood, hand saws for larger wood. Use loppers (long-handled pruners) for cutting up branches for the trash can.
  • By-pass type hand-pruners have a scissor type action, where the two blades pass each other by. This is far better than hand-pruners where a straight blade comes down on an anvil.
  • If you can't use hand-pruners to cut through a branch without a lot of effort, use a saw to make the cut. If you have to twist and crank on a cut, you will bruise (kill) the wood that remains behind.
  • Always use hand-pruners with the narrow blade next to the wood that is being left on the tree. This prevents unintentionally leaving stubs behind.

A Few Other Thoughts

  • When purchasing a new tree, watch out for girdled (circling) roots. These can cause the tree to fail later in life, often much later. Girdling roots occur when a plant is left in a container too long. Always wiggle the trunk a bit in the pot or box, and see if a 'plate' of soil heaves, indicating it is girdled from when it was in a smaller pot. When planting, after removing the plant from the container, make vertical slices through the root-ball about 1 inch deep, and every 6 inches, all the way around. If you hit a large root, cut it!
  • Younger is better when planting new trees. Younger trees are more adaptable, establish better, and usually end up healthier and out-grow larger specimens. Plus, you save money. I think 15 gallon trees are an ideal size, but even younger is better.
  • Trees need deep, wide irrigation. Make sure your tree has access to water beyond the immediate root-ball. Extra emitters should be added. The larger the tree will become, the more emitters it will need. Other plants with their own emitters can add to the trees wetting pattern, for plants share root space. The roots should be encouraged (through wetting patterns) to radiate out in all directions, for they will provide the physical support to keep the tree upright in high winds.
  • Think of irrigation in two parts; how much and how often. The difference between a Mesquite (low water user) and a Magnolia (high water user) is not in how much water they should receive when irrigated; each should be watered deep and wide. The difference is in how often each should be watered, with the Magnolia watered frequently, the Mesquite very occasionally.
  • Desert tree species do much better with infrequent watering. They are stronger, healthier, more attractive, require less pruning, and are more cold-hearty.

 

Screwbean near turf This is the Screwbean Mesquite growing near the turf (grass). The shovel is in the photo for scale. This tree is only 1 year old from a 15-gallon container.

 

 

 

Screwbean not near turf This tree was the same size and planted at the same time as the one near the turf. It is not near turf and I last watered it in October. It is half the size of the one near the turf, and in the long run, it will be the much more healthy and beautiful of the two, and require far less work (unless I get rid of the turf by the other one. Hmmmmm, there's an idea!)

  • Staking is only temporary. The stake that is against the trunk should be removed the day it is planted. Stakes should only be used if necessary to hold the tree upright or keep the root ball from shifting. Such stakes should be outside the root-ball, and cut short enough so that the stakes do not cause injury by rubbing against branches in the canopy. Stakes should be removed within 1 to 2 years.
  • Plant at proper depth. This is usually where the plant is in the pot - keep the soil level the same. To check, wiggle the tree in the pot. Where it pivots is at the point where it should enter the ground. If there is soil above this point (making the trunk look like it' 'wallowing' around) then its planted too deep in the pot, and plant it to the correct depth (the point of pivot). Another sign of the right depth to plant is root-flare, a spreading out of trunk tissue right where it enters the ground and transitions into roots.
  • Remember that pruning is a long-term process. Not all pruning objectives can be achieved in the first year. Plan ahead, years ahead. Know that small branches grow and become large ones. Use vision and imagination to determine what to prune now, and what to prune later.
  • And don't stress! Gardening should be fun. Plants recover from mistakes. If a branch is removed that leaves a hole in the canopy, plants naturally fill in those holes with new foliage. Take your time. If you're not sure about a cut, wait and think about it. Don't stress!