What is Necessary in Selecting an Alder Site

Information Sourced from wafarmforestry.com

Wild alder seed can fall on a variety of sites and out-compete Douglas-fir in its early years of growth. It is not uncommon for alder to grow 6 feet in its second year of growth. On the other hand, if the Douglas-fir can keep up with the alder for 15-20 years, then it will outgrow the alder in the long run. However, planted alder does not grow and react the same as wild alder. We have learned that planted alder has some very specific requirements.

It needs a well-drained soil, yet not one that would be considered as droughty.  Definitely do not plant it in a swamp, an area of poor drainage, or where there is standing water in winter. 

Absolutely avoid any possibility of a frost pocket.  This may be difficult to determine if the area has just been harvested and you don’t know the frost history in that area.  Look for pockets or depressions in low areas near the bottom of a slope.  If there are recent harvest units nearby, then look at the Douglas-fir seedlings for signs of frost damage (burned needles or damaged terminals).  If you see frost damage on adjacent Douglas-fir seedlings for 50-100 feet above the valley floor, then it is likely you will have the same in your proposed alder unit.  Douglas-fir is a little more frost hardy and can continue to grow from new buds after a frost so eventually it will outgrow the frost pocket.  The damage to the alder is generally too severe and it usually will not outgrow it. 

Also avoid summer drought and heat stress by picking the right slope.  South and west slopes will be the hardest on young seedlings in the Pacific Northwest.  South and west slopes also have increased wind damage potential. 

Alder also needs to be planted on very high site land, the same land where you would plant Douglas-fir. 


Alder Assessment Form 

Dr. Connie Harrington, researcher for the U.S. Forest Service, wrote an excellent publication to help determine where to plant alder. “A method of site quality evaluation for red alder”

Complete the form in this publication to get a better idea of what makes a good alder site and if you should proceed with alder or plant an alternate species.

View the video presentation “Where should I plant red alder?”, by Dr. Harrington, above.

Things to Consider Before Growing Alder

Check your soil for droughty conditions (heavy to sand could be considered as droughty). A droughty soil (not a technical term) can cause the stand to shut down or severely reduce its growth at a very young age when it should be producing at its highest growth rate.

Alder is very particular in where it grows. Natural seedlings may germinate in places where nursery seedlings will not grow (or at least grow well).

It is very sensitive to most vegetation site preparation and release chemicals.  However it still needs a chemical site preparation in order to get established.  To get a recommendation on chemical use, look in the Northwest Woodlands magazine for chemical company contact information. (Join WFFA to get Northwest Woodlands)

As already noted, it is important to complete Dr. Harrington’s alder site assessment form to insure you are really planting in a site.

The wood is very soft, breaks easily, and is almost impossible to fall it without some breakage.

As a result of easy breakage it is very susceptible to wind, ice, and snow loading damage.  Nothing will bring an alder plantation owner to tears more than a young plantation that appears to be demolished from heavy ice and/or snow.

Around 1995 the Pacific Northwest had a severe cold spell that lasted a week or more, long enough to freeze most juvenile trees and branches.  Near the end, a warm front rode up over the cold layer and rained heavily on all the frozen vegetation and ground, adding additional ice to the tree and branches.  Douglas-fir limbs 2-3 inches in diameter broke and fell to the ground.  But the most severe damage was to the alder and other hardwood stands.  The alder broke off at 4-5 inches in diameter, wiping out the entire tree top.  It was very sad to drive the local roads and see all the shiny new broken tree trunks sticking up through a mass of broken limbs and tree tops.  A similar storm hit the Portland, OR, and south area following a winter snow storm in 2021.  A tremendous amount of damage was done to alder and other hardwood species from that ice storm. 

More post-harvest waste (limbs and other woody debris) is generated than with Douglas-fir harvests (The limbs may break down faster than Douglas-fir, but you will have to deal with it at planting time.) 

The advantage of growing short rotation alder may be lost if it is mixed with Douglasfir in the same unit, as it is not practical to harvest the alder at 30 years of age and then come back in 10 years and harvest the Douglas-fir that was intermixed with the alder. 

Alder is even more susceptible to frost as a young seedling than Douglas-fir, so frost-free sites need to be found.  It is recommended that planting be done after all chance of frost has passed.  If you do get a frost you may lose a lot of your seedlings!  However by waiting you also may face drought conditions that late in the spring.  The weather patterns have been changing over the last few years, and there have been several recent summers when very little rain fell from March to September, which is very hard on newly planted seedlings! 

Alder seedlings are generally grown for one season in the nursery and even then they will be 3-4 feet tall at the minimum.  When the seedlings are that tall, the planter can only pack a few at a time, so a lot of time is spent going back and forth for trees, and it takes a lot of extra care to plant them properly.  Hiring a contract crew may be expensive!  

All plants are phototropic, meaning they grow towards light.  Alder is especially prone to grow toward light, especially if grown with clumpy spacing or with large openings. As a result, the bole will have an increased sweep, which can often be seen along forest roads.  A well-spaced stand will help minimize this tendency.