Eastern Cottonwood

Year-round

Eastern cottonwood is a big, fast growing, thirsty tree that needs room away from the house, and its brittle wood means it benefits from a periodic look-over.

• Give it full sun and soil that stays on the moist side. It tolerates both wet spots and short dry stretches once it is established.
• This tree grows fast, often several feet a year, and can become one of the largest trees in a yard, in the range of 75 to 100 feet tall or more with a wide canopy. Plant it well away from the house, driveway, septic system, and sewer lines.
• The wood is naturally weak and brittle for its size. Have a certified arborist look over the canopy every few years and after any major storm.
• In the Milwaukee area, eastern cottonwood is a native tree, most common in the southern part of Wisconsin, and it is a caterpillar host plant for the viceroy, red-spotted purple, and mourning cloak butterflies, so it is doing real work for local wildlife.
• Only female trees drop the cottony fluff the tree is named for. If a new tree is ever being chosen, a male, 'cottonless' variety skips that mess, though that choice does not apply to a tree already in the ground.

Fall

Fall, after the leaves drop, is one of the two good windows in Wisconsin for structural pruning on this tree.

• Leaves turn yellow and drop through fall like most shade trees in the area.
• Once the leaves are down, it is a good time to have an arborist remove dead, crossed, or storm damaged branches while the tree heads into dormancy.
• A newly planted tree benefits from one deep watering before the ground freezes for winter.
• No fertilizer is typically needed for an established cottonwood in ordinary yard soil.

Getting fallen leaves raked up in fall keeps the yard looking cared for going into winter.

Winter

Winter in Milwaukee is the best time for any real pruning cuts, and it is worth protecting a young trunk and checking for storm damage.

• Deep winter, while the tree is fully dormant, is the best window in Wisconsin for structural pruning. Disease organisms are least active in cold, dry weather, so cuts heal cleaner.
• This tree's wood is more brittle than most shade trees, so after any ice storm, look the canopy over for hanging or cracked branches and have them removed before they fall on their own.
• On a young tree, wrap the trunk with light colored tree wrap or hardware cloth from the ground up to the first branches. This guards against winter sunscald and against rabbits or deer chewing the bark while the ground is snow covered.
• No watering or fertilizing is needed once the tree is dormant.

Spring

Spring in the Milwaukee area is when to finish any structural pruning and watch for the flowers that come before the leaves fill in.

• If pruning was not finished over winter, get it done before growth kicks in. Once the tree leafs out fully, wait until the tree is dormant again for anything beyond small touch-ups.
• Small greenish flower clusters appear before the leaves come out, typically in early spring in this area. This is normal and needs no action.
• Walk the canopy for any branches that cracked or hung up over winter storms, and have those removed promptly, since this tree's wood breaks more easily than most.
• Give a newly planted or young tree a deep watering if spring turns dry. An established tree usually does not need the extra water.

Summer

Summer is cottonwood fluff season in Milwaukee, plus a time to watch for a few leaf issues in the humid weather.

• Female trees release their cottony seed fluff around late May into early June. It shows up in gutters, pool filters, and along fence lines for a couple of weeks.
• Keep an eye out for leaf spot, rust, powdery mildew, aphids, or scale, especially during Milwaukee's more humid summer stretches. Most of these are cosmetic on an established shade tree and do not need treatment.
• Water a young tree during dry spells. An established tree in moist soil usually gets by on rainfall alone.
• Skip major pruning cuts right now. Warm, humid weather makes it easier for disease to get into fresh wounds, so save real cuts for the dormant season.

Raking up the cotton fluff every few days while it is dropping keeps the yard and sidewalk looking tidy for the neighborhood.