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Garden & Home

Plant a micro-forest

A micro-forest is a dense planting of native trees and shrubs in a small space. It creates habitat from almost nothing, cooling the surrounding area, supporting pollinators and birds, and improving biodiversity within cities. Cities from Los Angeles to Mumbai are doing it. You can too.

Why it matters

Urban areas are getting hotter. Concrete and asphalt absorb solar heat during the day and release it at night, creating urban heat islands that can be several degrees warmer than surrounding rural land. Trees are the most effective tool we have to counter this. A 2025 systematic review of 115 studies found that urban trees consistently outperform all other vegetation types in cooling, particularly in hot, dry climates.

A micro-forest takes this further by planting at high density using native species, an approach inspired by the method developed by Japanese botanist Akira Miyawaki. Rather than isolated trees or manicured lawns, a micro-forest creates a layered, functioning ecosystem with canopy trees, understory trees, shrubs, and ground cover all growing together. Research on dense urban green spaces shows they can reduce local air temperatures by 1 to 7 degrees Celsius compared to surrounding paved areas.

Cities including Los Angeles and communities across the Bay Area are beginning to adopt the approach as part of urban heat resilience strategies. Mumbai has planted over 78 micro-forests since 2020. The method works at any scale, from a schoolyard to a back garden.

A note on the science: the specific claims sometimes made about micro-forests — such as maturing in 20 years or becoming fully self-sustaining after three — are not yet well supported by long-term research. What is well established is that dense native plantings support biodiversity, cool urban areas, and improve soil health. We describe what the evidence supports.

How to do it

  1. 1Choose your site: a micro-forest can be planted in as little as 100 sq ft (or 9 square meters). Look for underused lawn, a neglected corner, a verge, or a parking strip. Avoid areas with deep shade from buildings or overhead lines that would limit growth.
  2. 2Research native species for your region: using native species is the most important factor. Use your state's native plant society to find trees and shrubs native to your ecoregion. Aim for a mix of canopy trees, understory trees, shrubs, and ground cover.
  3. 3Prepare the soil: remove existing grass and weeds either by sheet mulching with cardboard or by physical removal. Amend the soil with compost to improve structure and encourage root development.
  4. 4Plant densely: plant at high density, around 3 species per 10 square feet (or per square meter), mixing species randomly rather than in rows. This density creates competition for light, which drives upward growth and accelerates canopy formation.
  5. 5Mulch heavily: apply a thick layer of mulch across the entire planting area. This suppresses weeds, retains moisture, and gradually improves soil biology as it breaks down.
  6. 6Water and weed for the first two years: water regularly during the first summer, especially during dry spells. Remove weeds that establish in the first two years before they compete with young trees. Once the canopy closes, maintenance reduces significantly.
The bigger picture

Most of the world's population now live in cities. When micro-forests are planted at neighborhood scale they create connected habitat corridors, reduce stormwater runoff, improve air quality, and give urban wildlife somewhere to live. Each patch of dense native planting contributes to a larger network.

Sources: Alonzo et al. (2025), Arboriculture and Urban Forestry; Manso et al. (2025), Science of the Total Environment; Ettinger et al. (2024), Scientific Reports; KneeDeep Times (2024).