Managing tamarack forests

You can find tamarack in pure stands, but it’s more common in mixed stands, primarily with black spruce. You’ll also find tamarack mixed with northern white cedar, black ash, red maple, eastern white pine and/or paper birch.

Tamarack commonly grows on bogs or peatland where the organic soil or peat is more than 12 inches thick. You’ll find tamarack on a wide range of peatlands, but it’s usually found in poor swamps where soil water is weakly enriched with mineral nutrients.

The best sites are:

• Upland sites.
• Moist, well-drained loamy soils along streams, lakes or swamps.
• Mineral soils with a shallow surface layer of organic matter.

Competition from more shade-tolerant species often quickly eliminates tamarack from these sites. Because of this, we find tamarack in Minnesota wetlands that other species don’t tolerate. While tamarack can tolerate wet sites, it won’t survive prolonged flooding.

A rotation is the number of years required to establish and grow trees to a desired size, product or maturity.

Depending on the site location and characteristics, tamarack will produce timber that’s fit to be sold on a rotation between 40 and 90 years.

• The best seedbed is a warm, moist mineral or organic soil with no brush, but a light cover of grass or other herbaceous vegetation.
• Hummocks of slow-growing sphagnum moss often make a good seedbed.
• Most seed falls within 200 feet of the seed tree.

Orient harvest strips so they’re perpendicular to the wind. They can be up to 200 feet wide.

After clearing the first strip, wait about 10 years or until the area is well-stocked with seedlings. Then, clear a second strip adjacent to the first and on the windward side. Again, wait until regeneration is established, then use the seed-tree method to cut the remaining strip.

The seed-tree cut should leave about 10 well-spaced dominant tamaracks per acre. Once the regenerated trees have been established, harvest or kill seed trees. This eliminates competition and possible disease hosts.

To ensure tamarack can regenerate, you may need to prepare the site following a harvest. Broadcast burn mixed-species stands to remove the branches and treetops left on the ground (known as slash).

Tamarack slash doesn’t burn well. So to remove it, harvest pure tamarack stands by full-tree skidding — meaning, cut the trees and then transport them with their branches and top intact. Then, treat the brush with herbicides. Alternatively, you could pile and burn the slash or shear or chop the brush.

Tamarack seedlings need abundant light and constant moisture. Seedlings established under a fully stocked stand won’t survive beyond the sixth year.

Early seedling losses are caused by damping-off fungus, drought, flooding, inadequate light and snowshoe hares. Given enough light, tamarack is one of the fastest-growing conifers on upland sites.

The larch sawfly is a serious insect pest of tamarack. After several years of defoliation, the sawfly can stress and eventually kill a tree.

Many forms of chemical control are available. Depending on the outbreak’s severity, you may need these to manage sawfly populations.

There aren't any changes you can make to the natural environment to control sawflies. But, as with all defoliating insects, it’s important to maintain healthy trees to minimize the stress caused by defoliation.

The eastern larch beetle is a native bark beetle that has infested considerable forests across northern Minnesota.

To minimize damage, encourage a mix of tree species and ages.

• This reduces how many host trees are available. 
• Makes it harder for the pests to get needed resources. 
• Limits the beetle’s ability to survive and spread.

Eastern larch beetles don’t typically attack seedlings and saplings.

Tamarack is susceptible to root and heart rots. You can minimize rots if you avoid damaging the base and roots of trees during intermediate cuttings.

Porcupines can cause extensive damage to tamaracks by feeding on the main stem’s bark.