Question

What are some indigenous, low-maintenance, yet attractive options for the concrete planters at my son's NYC school?

Asked by Dina
New York, NY

The green committee at my son's NYC school would like to use the concrete planters already on-site. Looking for indigenous, low-maintenance, yet attractive options (relatively inexpensive too). Previous attempts (non-green) to plant have not been successful. Planters are mostly in the shade (and unfortunately are sometimes subject to dogs urinating and people spilling coffee into them). Please help!

Answer

Richard Heller

Answered by Richard Heller

New Rochelle, NY

Greener by Design

March 13, 2011

When you are talking about plants and maintenance, size matters; no-maintenance plantings occur only in nature or in wide swaths of land for the most part. 

  • The more you break up "nature" or the many layers of an ecosystem that regulate it and sustain it, the more intervention or maintenance is necessary to sustain it.
  • The smaller the soil area, the higher the maintenance, and when you throw in terms like green and sustainable, the issue becomes even more complex.

What is Green?

Definitions of green/sustainable are fairly broad, and there are contrasting views. For example, there is a contingent that believes nuclear power is more "green" than energy derived from oil, and vice versa. There is a great deal of debate about what green is. This is even true in the wonderful world of landscapes.

Some factions would argue that any planting is, by its nature, green; others would argue that only native/indigenous plants are green, and yet another group might argue that only plantings that are self-sustaining, or needing minimal human intervention, are green. 

Soil is like a sponge

It is clear that native/indigenous plantings and low maintenance are important to you.

However, please remember that plants do not normally grow in concrete planters isolated from a larger ecosystem. New York City is a completely obliterated ecosystem that is, hopefully, being slowly rewoven. 

What that means is that plants isolated in a concrete planter by definition can't be low-maintenance

  • Even a very large planter -- let's say 48" in diameter, which is probably the largest planter allowed by the NYC Department of Traffic (and usually used to stop trucks from crossing the sidewalk) -- will need frequent watering (at least twice a week).
  • Soil is like a sponge: the more of it there is, the slower it dries out.
  • Soil isolated in a planter will dry out much more quickly, especially since the plants will be drawing from the soil at the same time.

Nutrients in the soil

Additionally, plant material will continuously absorb organic materials and release them in the form of leaves being shed or pruned off over time, so organic material will need to be put back into the planter on a regular basis. Being "green" in the context of planter soil means nurturing a live layer of humus. 

The planter will need regular infusions of composted manure and/or compost tea so that there is soil biology to help the plant(s) digest the organic material.

Given the dumping of coffee and potential "canine interventions," even more water may be needed to flush the soil, which means that nutrients will be flushed as well and the soil will require regular application of nutrient-rich organic material such as composted topsoil.

Planter function

In a nutshell, planters are not terribly sustainable or green. However, in a sterile urban environment, they are an oasis and they do help re-knit the damaged ecosystem that people have wiped out in constructing buildings and roads.

They are alive, they provide oxygen and beauty, they can serve as homes for beneficial insects.

Additionally, the more greenways, green roofs, roof gardens, street trees, and planters there are in a concrete scab like New York City, the more opportunity there is to reconnect this very limited ecosystem with the slightly less damaged ecosystems of the suburbs and begin to re-weave that which we have unraveled.

What may survive, and why planters require care

The plants that will survive in a planter are contingent on how large the planter is. Any planter smaller than 24" will not sustain a tree, for example, and even planters larger than that will only sustain trees as long as those trees are regularly root-pruned and shaped.

And now for the really painful part. The reason so many urban plantings are made up of non-native and even invasive plants is because often non-native plants -- like taxus for example -- survive in harsh, low-maintenance conditions better than the natives do. 

When you take native plants out of their natural community, they are weakened and vulnerable. Basically, as the caregiver to the planter, you become their community and if you are unwilling to maintain them, they will die. Our indigenous plants developed in a woodland environment of interdependent trees, shrubs, perennials and ground covers. Studies have revealed that all these plants share water and have systems of chemical communication in which they warn each other of disease and insect infestations so that the other plants can chemically adjust to become less attractive to the infestation. Additionally, they share water in drought. 

I am not advocating that we give up on natives, but pointing out that when you combine low maintenance and indigenous in a container in New York City, you now have a very short list. This list is further reduced by the size of the planter and the need to have the planting be attractive.

Plant recommendations

So here it is: If you are looking for ornamental deciduous trees, I would recommend crabapples, amalanchier or perhaps risk a native dogwood. These will bloom for you, and even fruit -- which the birds will like. A longer list of small native ornamental trees is available at the Tree Notes blog.

For shrubs, the only native evergreen that really holds up is Manhattan euonymous, which is a great shrub for beds, but not so great for planters as they lack structure unless grown in a specific form, like an espalier for example. They are also prone to scale when maintained poorly. 

  • A list of more shrubs can be found at the Lady Bird Johnson Wildflower Center website.
  • If you're looking for seasonal color then you might as well throw out natives altogether, as these will mostly be perennials and have very limited bloom time.
  • However, if you are interested in native perennials you can get a list of natives for any state here.

Tagged In: native plants

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