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Crab Apple Tree Problem

I inherited a young crab apple tree problem. Last year it didn't do very well and lost a lot of leave and had dead branch tips.  This year it also has not done well. It has lost leaves but new ones are now growing AND this is the question: it has small (size of a dime) buds of hard clear sap (?) at branch intersections or dead branches. What is causing this?

Plant Growing Conditions: Zone 8, full sun, thought water may have been the problem last year so have made sure it has had plenty this year.

What I've done already: Didn't know what to do so just made sure it was watered well.

Doug says:

OK - the good news is that water is indeed the key here.  Leaf drop is, for the most part, a function of stress (assuming it isn't fall leaf drop) and water is the most likely culprit in most cases. Sometimes it is too much water but in most gardens under natural watering regimes, it is too little (figure about 1.5 inches/week - if you have plants under the tree - figure 2 inches/week)  I use a .99 rain gauge cup to measure and make sure I track the amount of water the garden gets.

So your watering has "solved" the problem and reversed the trend.  If the tree has started regenerating - you're winning.  Toss some compost around the drip line of the tree (approx 2 feet inside the drip line and 2 feet outside the drip line) this fall.  The drip line is where the water would fall from the tree if the leaf canopy were solid and waterproof- the outer edge of the tree branches.  Compost this fall is going to help more than a spring feeding (trees make major root growth in the fall and over the winter below frost line)  A strong root system is key to making sure this plant survives.

If you don't have compost - use a fertilizer with NO nitrogen but equal (or close) parts phosphorus and potash around the dripline to get those nutrients to the plant.

So water and compost.

As for the hard nodules. They're solidified sap.  This happens with malus (apple) at the best of times in younger plants and particularly if stressed.  There are saps associated with different rings  of the tree (phloem sap, xylem sap) - it isn't one sap flow inside the trunk.  When minute cracks appear in the bark, then sap leaks out.  Insects such as ants consider young apple trees a marvellous food source for this reason. They aren't bothering the tree, they're eating all that sugary sap.  So ants don't cause the problem, they take advantage of it.

So you'll see it on young trees (particularly fruit) without concern.  Lots of it means stress again.  As I understand the mechanics, a water stress creates some "shrinking" or hardening of plant connective tissue and there are more minute cracks in the bark as a result - hence more nodules of dried sap.  I'm not sure of the mechanics of this but there also may be some "drying out" and production of air pockets in the sap flow - this leads to some mechanical pressure problems within the trunk and possibly "ejection" of sap through minute cracks.  But in any case, water stress will lead to more sap leakage.

But you can trace all the problems back to stress within the plant.  And you've likely identified water as the culprit here.


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