Tree Maintenance

Tree Pit Gardening

blue tomato tree pit garden

Image courtesy of Blue Tomato Design.


When a new, tree is planted in front of a home or business, 30 square feet of new planting space comes with it in the tree pit. Perennials, annuals and bulbs are beautiful additions to a tree pit, as long as you remember that the tree’s health comes first. Well maintained tree pit gardens enliven the public right of way along your block, throughout the neighborhood, and in business districts.  (Disclaimer: the City of Pittsburgh requires an encroachment permit for anything planted or installed in the right-of-way.  While this rule has not been enforced for gardens, Tree Pittsburgh wants you to be aware of it.  Every tree planted in the right-of-way has an encroachment permit already.)

Tree pit gardens

  • Can dissuade dog owners from letting dogs “use” the tree pit
  • Remind the owner to water the plants and the tree that was recently planted
  • Prevent cyclists from locking bikes to a newly planted tree
  • Look great

Guidelines for Tree Pit Gardening:

  • Do not plant vines or plants that will creep up the tree trunk or onto branches.
  • Plant at least one foot away from the tree’s trunk so as not to disturb the roots there.
  • Plant shallow rooted plants that won’t compete with the tree’s nutrients.
  • Remember to water the tree pit enough so that both the plants and the tree get water!

Tree Pit Approved Plants

• Choose plants that require little watering. Key words to look for are “drought tolerant” and “xeric conditions”.

• Use small plants and bulbs – large plants require large planting holes, which damage tree roots. In addition plants with large root systems compete with the tree for water and nutrients.

• Do not add more soil to your tree pit. Raising the soil level will harm the tree. • Mulching a tree pit is always good for your tree and plants. Mulch keeps the soil moist and prevents weeds from sprouting in tree pits.

NEVER PLANT! Bamboo, Ivy, Vines, Woody Shrubs, Evergreens or Invasives! They are all major competitors for water and nutrients and can stunt or kill a tree.  See a list of invasives in Pennsylvania here


Bulbs are a nice addition to tree pits, and neighborhoods often plant them in the fall during tree plantings. Many Bulbs will return each spring, bringing color to your neighborhood. They are both affordable and easy to plant.

Plants for the Sun, Good for newly planted trees

   Annuals--plants that live only one year and need to planted annually:

  • Sweet Alyssum (Mat forming, small yellow or white flowers)
  • Dusty Miller – Senecio cinerara (Beautiful snow white and shiny silver color)
  • Licorice Plant Helichrysum
  • Marigold
  • Nasturtium
  • Portulaca-Rock Rose, Moss Rose (Good drought tolerant plant)
  • Verbena
  • Geranium (An old standby that requires little water)
  • Scented Geranium (For leaf form, color and small flowers)
  •  Salvia
  • Snapdragon
  • Heliotrope (Beautiful scent)
  • Cosmos (Dwarf – height 24”)
  • Ageratum (Low growing with small purple flowers)
  • Blue Marguerite Daisy 
  • Lantana (A variety of unique flowers)
  • New Guinea Impatiens

    Perennials (plants that live for more than one year):


  • Ox-eye Daisy chrysanthnum leucanthemum (Beautiful white flowers)
  • Bugleweed Ajuga reptans
  • Snow in Summer Cerastium tomemtosum
  • Lilyturf Liriope muscari
  • Sedum Sedum albuonor acre (Only low growing)
  • Thyme Thymus serpiphylluur or pseudolanugipsus (Mat forming varieties)


Plants for the Shade, Good for newly established trees

    Annuals-plants that last one year and must be planted annually:

  • Begonia (Elegant flowers that come in a large variety)
  • Coleus (Variegated foliage, purple flowers)
  • Lobelia (Small edging plant)
  • Pansy (Some are winter hardy)
  • Viola Torenia (Looks like a small pansy)
  • Impatiens (Popular colorful flowers that will do well in your tree pit, sun or shade)
  • Monkey Flower Mimulus (A variety of colorful flowers)
  • Browallia (Fabulous blue color)
  • Fuchsia (Variety of species, most annuals bear a red tubular flower)

Perennials-plants that come back year after year

  • Elephant’s ears Bergenia cordifolia (Holds good winter color)
  • Coral Bells Heuchera
  • Spotted Deadnettle Lamium maculatum (Excellent groundcover)
  • Lilyturf Liriope muscari(evergreen)
  • Foam Flower Tiarella cordifolia(Vigorous groundcover with white upright flowers)
Plant suggestions for tree pit gardens came from the New York City Parks & Recreation Website.


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Basic Tree Maintenance

What do trees need?

Trees need regular maintenance to ensure their long-term health and safety in our landscapes. The urban environment is the source of many stressors on trees; from asphalt reflecting excess heat, to the salt we put down in the winter time. Trees do not usually encounter these stresses in their natural environment and they can often lead to poor growth or even death of the tree if they aren’t properly addressed. To help our urban trees grow large and live long productive lives, there are many things that we can do to help out.


Keep your trees healthy and learn more about basic tree maintenance on these pages (coming soon):

  • Mulching
  • Watering 
  • Pruning


Seasonal Maintenance:

  • Winter Maintenance
  • Spring Maintenance
  • Summer Maintenance
  • Autumn Maintenance
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The single most beneficial thing you can do for any tree is to mulch it properly.


Mulching is the application of material on the ground in an area where plants are growing.  Various materials can be used according to the desired outcome. 

In natural settings, trees drop their leaves right around themselves and can absorb nutrients as they decay.  In this way, trees treat their waste as food-recycling the nutrients that they lose in their leaves each year to help grow new leaves in the future. 

In the city, we plant trees in what are frequently compacted, unnatural soils surrounded with concrete, gravel and are often subject to littering and animal waste.  Mulch improves the tree’s living conditions in the city; it breaks down to provide nutrients for the tree, while also yielding a host of other benefits.


“How much should I mulch?”

The more area you mulch, the more your trees will benefit.  Landscape standards generally call for mulching to the ‘drip line’ of the tree, or to the edge of the tree’s leaf canopy.  This may be impractical if you have a large tree in your yard whose canopy spans the entire lawn, so a smaller circle may be more appropriate.  The more area that you mulch the greater long-term improvement in tree health and growth you will see.

Street trees that are planted in 3X10 tree pits receive the most benefit from mulching the entire 30sqft area.


“How thick of a mulch layer should I apply?”

Mulch wide, not deep, and do not allow mulch to touch the trunk of the tree. 

It is extremely important NOT to volcano mulch!  Mulch a wide ring in the shape of a donut, and do not pile the mulch up against the trunk of the tree.  Most mulch is comprised of decomposing wood chips. The organisms breaking down those chips don’t know the difference between the mulch and the tree, so theycan lead to decay in the tree itself if the mulch is in contact with the trunk/root flare.

Also, applying an excessively thick layer of mulch can limit oxygen in the soil and suffocate the tree!


“What kind of material should I use?”

Tree Pittsburgh uses strictly hardwood mulch. This is a local product made up of old trees, wood pallets, saw mill waste and other ‘recycled’ wood that has been chipped up into small pieces. This material breaks down at a good pace and stays put when applied in tree pits. Pine bark mulch is great, but tends to wash out of tree pits too easily.

We do not recommend cypress or rubber mulch!

Cypress mulch is not a sustainable product and should be avoided.  Cypress trees are removed from around the Gulf of Mexico, and hurricane prone areas suffer greater damage in storms as each one is removed.

Rubber mulch does not provide many of the benefits mentioned above. It will not decompose and will remain mixed with the soil for many, many years. There is speculation that rubber mulch may absorb heat and cause damage to the tree.

Happy mulching!


Thanks to Tirzah Griffin for the mulch and tree planting photography!


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