Consider Watering Your Street Trees

I have a dorky habit to confess. Whenever my to-go iced coffee is finished, I dump the ice from my reusable cup into the dirt of a street tree. It’s probably like half a cup of water, and I am sure it doesn’t make a difference, but I can’t not do it.

I mention this in light of news from the United Kingdom about a campaign to rally the public to water new street trees.

While this specific campaign—which is a collaboration between the Arboricultural Association and the Woodland Trust—is addressing trees in the UK, it’s an action that can be done everywhere there are street trees in need.

The UK Government has committed to planting millions of trees to help meet climate and nature targets and aims to increase tree cover in England from 14.5% to 16.5% by 2050. Likewise, cities across the United States have similar tree-planting goals.

The Hard-Knock Life of Street Trees

Alas, rising temperatures, droughts, and dry spells lead to an increasing loss of new street trees.

As John Parker, chief executive of the Arboricultural Association, says:

“Planting a tree is just the start of the story. The health and survival of new urban trees is threatened by increasingly dry weather.  It is recommended that newly planted trees are given 50 litres [13 gallons] of water per week during the summer months, for the first three years. You can help ensure healthy trees for the future over the summer months by watering trees near you.”

As echoed by the New York Botanical Garden (NYBG), probably the biggest problem street trees face, especially young trees, is drought. “Trees need 8 to 10 gallons of water a week to stay healthy, with young trees benefiting from 10 to 20 gallons while they are getting established. You can help keep street trees alive during dry periods by watering generously once a week.”

The Importance of Urban Trees

Long ago, before I knew better, I assumed that benefit of street trees was to soften the aesthetic and emotional hard edges of urban environments. But wow, what an underestimation of tree power that was.

A 2021 study from the University of Minnesota does a great job of laying it all out. The authors cite a study that aligns with my early thoughts about urban trees: “To some, trees are important for aesthetics and placemaking; they can convey a sense of connection to history, provide inspiration, or a calming peaceful atmosphere in an otherwise turbulent, crowded city” But the authors also cite other research to illustrate the benefits of street trees, noting that approximately 80% of Americans live in urban areas. Trees are responsible for:

• Lower home heating and cooling costs
• Increased property values 
• Lower summer ambient temperatures, which play an important role in combating urban heat island effects
• Air and pollutant filtration
• Increased air quality and decreased asthma rates 
• reduced and intercepted stormwater runoff 
• Increased air quality and decreased asthma rates 
• The ability to sequester carbon from the atmosphere

And I would add that the habitat they provide for wildlife—especially migrating and native local birds—delivers an invaluable mental-health boost to nature-loving urban dwellers like me.

The study delves into why so many urban trees die at a young age, noting that “the immediate years following planting are often the toughest.”

Catherine Nuttgens, head of the Woodland Trust’s urban tree program, explains that “while in rural settings, newly planted saplings and woods can take care of themselves and adapt, the challenging conditions presented by living in the built environment mean trees in our streets and urban areas need a bit more TLC.”

How To Water Street Trees

Go Slow

The Brooklyn Botanic Garden (BBG) advises watering slowly so the moisture sinks in and doesn’t simply run off into the street. “Set a hose to trickle water into the bed for an hour; or prick a few holes on one side of a clean garbage can, set it next to the tree bed, and fill it with your tree’s water allotment.”

Time of Day Matters

Watering should ideally be carried out in the early morning or evening.

Use Sustainable Water

Water should be sustainably sourced. Harvested rainwater is ideal, but bath water, or other grey water, is also suitable. Collect the cold water that usually goes down the drain while you're waiting for the hot water; use (only unsalted) cooled pasta water; if you're in a city that experiences open hydrants, grab a bucket and go to town, so to speak. You get the idea.

Plant Flowers

BBG also recommends planting flowers or groundcovers with shallow root systems around city trees, as they can help conserve moisture. “Avoid large shrubs and water-hungry plants that will compete with the tree. Instead, try planting spring bulbs like snowdrops, crocuses, and miniature daffodils (which are shunned by squirrels rooting for food). After they fade, small annuals with shallow roots like zinnias and impatiens, or perennial groundcovers like bugleweed or stonecrop, will keep the bed attractive.”

Other Challenges for Street Trees

While we are at it, thirst may be urban trees’ most evident challenge, but our stalwart city trees face plenty of other struggles in the concrete jungle. “The life of street trees is hazardous,” notes NYBG. “Vandalism, bikes being chained to them, car doors slamming against trunks, trucks hitting lower branches, garbage being dumped into tree pits and pets using tree pits as lavatories are just a few of the dangers.”

Trees can't run away or speak "human" (though a girl can dream). Unfortunately for them and fortunately for urban dwellers, city trees are stuck with us. If we want to continue enjoying all the good they do, we should try to understand their needs and do all that we can to support them. A few ice cubes won't do much, but next time you have a pot of water to dump, you know what to do.