Trees

Conifers

Evergreen trees are dropping needles. Is this due to rainy weather? Any management recommendations?

When a tree experiences a severe environmental stress, such as flooding, waterlogged soil or drought, during the growing season, it is common for it to drop its foliage and go into a quiescent, or false dormancy, phase. Waterlogged soil is probably more problematic for tree roots because it does not allow for normal respiration of the roots. It’s like trying to breathe underwater; it’s not possible. The longer a tree’s root system remains in this situation, the greater the risk of mortality.

The best approach to managing flood-stressed trees is to enhance their vigor by following proper tree-maintenance practices and eliminating additional stresses. Pruning (removal of dead branches and corrective pruning) should be delayed until the dormant season. Aerating the soil (by professional arborists) can help enhance vigor, but they are not rescue treatments for severely injured trees. Trees developing substantial dieback and decline symptoms or those possessing defects that decrease their structural integrity, which makes them more prone to windthrow and structural failure, should be removed from the landscape immediately. Also, keep in mind these waterlogged soils are excellent for soil-borne pathogens like Phytopthora to move freely in the soil from diseased trees to healthy ones. However, there is no good solution for this situation.

— Answer by Hank Stelzer

Deciduous

Deciduous trees are having premature leaf color change. Will this affect vigor or survival? Any management recommendations?

When a tree experiences a severe environmental stress, such as flooding, waterlogged soil or drought, during the growing season, it is common for it to drop its foliage and go into a quiescent, or false dormancy, phase. Waterlogged soil is probably more problematic for tree roots because it does not allow for normal respiration of the roots. It’s like trying to breathe underwater; it’s not possible. The longer a tree’s root system remains in this situation, the greater the risk of mortality.

The best approach to managing flood-stressed trees is to enhance their vigor by following proper tree-maintenance practices and eliminating additional stresses. Pruning (removal of dead branches and corrective pruning) should be delayed until the dormant season. Aerating the soil (by professional arborists) can help enhance vigor, but they are not rescue treatments for severely injured trees. Trees developing substantial dieback and decline symptoms or those possessing defects that decrease their structural integrity, which makes them more prone to windthrow and structural failure, should be removed from the landscape immediately.

— Answer by Hank Stelzer

Flood response

What are the best practices to identify and mitigate flood damage to trees?

It is really hard to determine if a tree dies from waterlogged soils or something else, such as a pathogen. Standing water is somewhat easier because you can see the water covering the landscape. Probably the best mitigation is soil aeration to assist in drying out the soil surface.

One other thing to keep in mind. Contrary to popular belief, the majority of a tree’s root system resides in the upper 12 to 18 inches of the soil profile. A lot of these roots are what are called fine roots and are responsible for water and nutrient uptake. These fine roots ‘turn over’ or regenerate every one or two years. Waterlogged soils force these fine roots to reside closer to the soil surface. Then, if we experience a severe drought the following year, the tree can experience severe drought stress. This happened recently; 2010 and 2011 were very wet years. Then in 2012 we experienced what the experts called a flash drought; severe dry soil conditions coupled with extremely high temperatures. Although trees are fairly resilient and can suffer the occasional defoliation, repeated environmental stresses will eventually lead to tree death.

— Answer by Hank Stelzer

What are some examples of flood tolerant and intolerant trees.

Tolerant: Acer rubrum - red maple; Fraxinus nigra - black ash; Fraxinus pennsylvania - green ash; Larix laricina - Eastern larch; Salix nigra - black willow; and Taxodium distichum – baldcypress

Intolerant: Acer platanoides - Norway maple; Acer saccharum - sugar maple; Aesculus flava - yellow buckeye; Asimina triloba - common pawpaw; Carpinus caroliniana - American hornbeam; Carya ovata - shagbark hickory; Cercis canadensis - Eastern redbud; Cladrastis kentukea - American yellowwood; Crataegus lavallei - lavalle hawthorn; Fagus grandifolia - American beech; Juglans nigra - black walnut; Juniperus virginiana - Eastern red cedar; Liriodendron tulipifera - tulip tree; Magnolia ? soulangiana - saucer magnolia; Malus spp. – crabapple; Nyssa sylvatica - black gum; Ostrya virginiana - American hophornbeam; Picea abies - Norway spruce; Picea glauca - white spruce; Picea pungens - Colorado spruce; Pinus banksiana - jack pine; Pinus resinosa - red pine; Pinus strobus - Eastern white pine; Prunus serotina - black cherry; Quercus alba - white oak; Quercus muehlenbergii - chinkapin oak; Quercus rubra - red oak; Sassafras albidum – sassafras; Sorbus aucuparia - European mountainash; Tilia spp. – linden; Tsuga canadensis - Eastern hemlock; and Ulmus pumila - Siberian elm

— Answer by Hank Stelzer

Industry

How is this wet weather affecting the timber industry in Missouri?

The last few months of wet weather have taken their toll on the timber industry in Missouri. Loggers do not like to spend their time recovering stuck equipment. More importantly, landowners do not want rutted roads and compacted soil. However, since the average wood basket is about a 50-mile radius around a given mill, you can imagine it is somewhat hit-and-miss. Anecdotal feedback I have received points to mills in northern Missouri and along the Missouri and Mississippi Rivers who harvest trees from woods on glacial till soils most severely impacted. The more prudent mills hold what are called wet weather timber contracts on parcels of land with more stable soils and located next to hard surface roads.

— Answer by Hank Stelzer