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Tree Pit Care

Drawing of Street Tree

A city tree must battle many urban hazards daily — from air pollution and bicycles to dogs and people. In addition to above ground threats, tree roots also must contend with tough below–ground conditions. A tree pit or lawn strip provides limited space for these forest giants and this soil is a tree's only source of nutrients. Because of this, it is essential to create as nurturing a tree pit as possible.

Guidelines

  • Using a hand cultivator, loosen the top 2-3 inches of soil to alleviate compaction and help water and air reach the roots.
  • Apply a three-inch layer of mulch, preferably shredded bark to the tree pit. Mulch keeps the water from evaporating quickly, reduces soil compaction, and improves the soil as it breaks down. Do not pile the mulch against the trunk of the tree; water will accumulate and rot the trunk.
  • The soil level around a tree should not be changed from the soil level at which it was planted. Adding soil (even 6 inches) can smother roots and rot a tree's trunk. Digging soil out can damage shallow roots.
  • Keep dogs and dog waste (both liquid and solid) out of the tree pit. The waste will overwhelm a tree, burning its trunk, and throwing the soil nutrients out of balance.
  • Remove unwanted competing plants, i.e. weeds.
  • Keep garbage and de-icing salt out of the tree pit. Try alternatives to rock salt (sodium chloride) such as calcium chloride or granular urea. In the spring, flush the tree pit with water to dilute winter salt buildup.
  • Don't lock bikes to trees or leave decorative lighting on past February.
  • Remove supporting wires if they are left on more than one year afterplanting.

Tools

  • hand cultivator or trowel
  • shredded bark mulch or wood chips
  • flowers or bulbs

Suggestions

  • If done carefully, you can plant flowers or bulbs in the tree pit (see separate sheet for recommended types). Flowers that have shallow roots and die back each year (annuals) will not seriously compete for limited resources. However, be sure to provide enough water for the tree, not just enough to perk up the flowers. Please do not plant flowers within one foot of the tree trunk.
  • Consider installing tree guards. Strong metal guards around the edge of the pit protect the soil by discouraging pedestrians and dogs from walking through the pit. Do not place tree guards close to the tree. Do not build solid walls; these encourage people to add soil to the tree pit (see above guideline). We do not recommend tree grates, the metal grating that sits flush with the sidewalk. Trash accumulates beneath the grates and trees that outgrow a grate can be fatally girdled or strangled.

Caring for Street Trees & Greenstreets

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