One of the main questions I get this time of year when talking with clients is: "You can't prune my tree this time of year, can you? My tree will bleed!". This is where tree terminology and proper education come into effect. LaRueTree Certified Arborists, Inc. was founded with a mandate to educate people about trees and how they fit into urban landscapes.
It is true, in Edmonton, Vegreville, or surrounding areas, in late winter to early spring, the sap in the tree starts to rise with warming temperatures, delivering water and sugar to the new leaf buds as they swell in readiness for spring. Like a balloon, or one of those party favours that you blow into, buds and leaves require pressure to burst open and unfurl. The saps upward push in the inner trunk (xylem) is in response to root water pressure, which is more intense in the spring than any other time of year (hence the importance of providing deep root water and fertilizer in our urban areas). Pruning limbs can cause sap loss in the spring.
But, have no fear! The sap loss is a minor issue for the tree. Even though stored energy is used to push out the substance, the greater loss is the removal of the tree branch - a part of the tree to which the sap would have supplied water and nutrients for energy and growth.
Also, excess quantities of sap running down a trunk or limb can attract harmful insects and disease fungi who feed on the sweet syrupy substance, but it is usually more of an aesthetic nuisance – especially when the sap drips on cars and decks. .
"I'm in the Edmonton Area, When should I Prune my Tree?"
The absolute best time to prune these “bleeder” trees is in early summer after the leaves have hardened or turned dark green. The sap will still run, but not to the point of depleting moisture and sugar from the tree. Since it is not a closed system, like a mammal, the tree will not “bleed to death”.
Late summer pruning is also discouraged because, although there will be no bleeding immediately following pruning, the non-healed cuts will begin to bleed as soon as sap begins to flow in spring.
But, this sap flow is mostly harmless, and as long as there is a good supply of moisture and nutrients in the ground, your tree will be fine!
Examples of prolific sap runner trees (Edmonton Area):
Birches (Betula)
Elms (Ulmus)
Maples (Acer)
Walnut (Juglans)
Poplars (Populus)
Willow (salix)
Sumacs (Rhus)
There is no practical method for stopping the flow of sap from a bleeding wound, and in most cases, this bleeding is completely harmless. Binding and wrapping the cut is not recommended, nor is painting it, as it is better to allow air to reach the wound and let it heal naturally. Trees are incredible, and never cease to amaze me with their complexity.
If you have any questions, please call me, or email me, I love to chat about trees!