Creating a Boulevard Garden
Gardening in the “hellstrip” can one of the most challenging, but rewarding, gardening projects you can tackle. A hellstrip is the narrow strip between the street and sidewalk, usually dry, barren and abused. Even the grass struggles to grow. Transforming your boulevard from a hellstrip to a welcoming garden will take planning and hard work . But properly done, the result will be a low maintenance oasis.
The challenges and solutions to gardening in the hellstrip are similar to gardening along hot blacktop drives and streets. And in the North and Midwest where snow removal and deicing salts creates a hellstrip all along our road easements, hellstrip gardening practices combined with the use of salt tolerant plants can help you create low maintenance curb appeal.
Poor soil lacking nutrients
Hard compacted soil
Laden with weed seeds
Often hot with intense sun exposure
Often difficult to water or out of reach with the garden hose
Water is not retained well in the sun and heat surrounded by hard surfaces
Repeatedly abused by snow plows and heaped with snow full of salt and or deicer
Assaulted by dogs, bikes, pedestrians and litter
Hellstrip, boulevard, and curb gardens are challenging, this should probably not be your first attempt at gardening
In both urban and suburban settings, cars will park along the curb and passengers will need room to get out. Consider ground covers or stepping stones in a one to two foot edge along the curb, which will also prevent runoff.
If your hellstrip is on a busy street with lots of parking cars, consider using “steppable” groundcovers, with small clusters of perennial plantings to minimize potential trampling
View of the street cannot be obstructed when backing out of a driveway
Planting should be low enough at maturity that small children can be seen by passing drivers
Plant survival may be trial and error, so you may prefer to use cuttings and divisions, unwanted plants moved from other gardens, or inexpensive plants until suitability is determined. Many inexpensive plants spread rapidly or re seed.
If a rain garden is not permitted or not possible, a low center will allow water to settle in your curb garden rather than run off, allowing you to use less drought tolerant plantings
If there are trees in the boulevard do not dig deeply under the canopy – shallow rooted perennials, groundcovers, or woodland plants are best suited under the trees. And do not add deep soil or mulch in contact with the trunk.
Finished top surface of your mulch should fall just below the curb level so that rain does not wash it into the street. Gravel mulch will not wash out so easily and is well suited to the type of plants used in drought tolerant gardens. Dense ground cover may be even better.
Most plants will require some watering in the first season until they are well established, but then drought tolerant plants should only be watered in severe drought periods
Many cities enforce ordinances about planting in boulevards and easements
Building up a berm or raised bed creates runoff issues and may violate storm water restrictions
Utility cables may be buried that must be located before digging
BEGIN WITH SOIL PREP
The single most important thing you will do is prepare the soil. It will be a lot of work. It will be hard work. But if you don’t do it well, you will NOT have a low maintenance curb garden, and your plants may not even survive. You should plan what type of plants you need for your specific situation so you can plan the soil preparation appropriately. Plants referred to as drought tolerant typically thrive in sandy, poor soils and prefer long periods without rain or watering.
Once you have determined the types of plants you will use, you will know how to prepare the soil. Here are some things to keep in mind:
All plants, especially drought tolerant, need good drainage. Most will not do well with “wet feet” caused by compacted soil too close to the root zone
Succulents do well in dry, infertile soil and thrive even when neglected
Many drought tolerant plants also do well in dry, infertile soil and also thrive when neglected
Most shade plants require moisture and may need regular watering or rain
If impenetrable hardpan is hit within the first six inches or so, only the most shallow rooted plants, such as succulents, should be used
In general, most drought tolerant plants will need a 6-12” depth of soil
Larger plants, such as shrubs or large perennials, may need quite deep soil prep
Areas that are too large to be entirely dug and amended can be prepped as single planting holes or for cluster plantings, using mulch or ground cover to fill the rest of the area
Your first tough job is to remove existing plant life including their roots. Many perennial weeds, including dandelions, will grow back from a small bit of root left in the soil. Strip sod, then dig up clods and break them up using a pitchfork, or claw and your hands to loosen plants and roots from the soil. Dispose of plant material and sift through the rest of the soil clods to remove roots and plant bits. (Do not put this debris in your compost heap unless you compost hot enough to destroy weeds and seeds.) Dig as deep as possible, using the double dig method. At bare minimum, soil must be thoroughly loosened with a pitchfork to a depth of 8 inches.
Even once this is complete, your soil is still full of weed seeds waiting for the chance to sprout. Once you complete your digging and soil prep, you can cover the strip with heavy clear plastic sheet, staking it at the corners, during a hot period. The intense heat produced under the plastic sheet will kill seeds and root remains in 4 to 6 weeks. If you skip this step, you will be spending some time pulling weeds in your “low maintenance” curb garden. Another alternative is to prep your planting area in fall, and allow the seeds to sprout next spring and early summer, eliminating them before you plant.
The most important part of preparing your soil is digging deep to loosen compacted soil. Young roots will not be able to push through compacted soil or heavy clay to become established, and water will not drain away from the plants, eventually drowning the roots. Organic matter can be added to clay or compacted soil to improve drainage. Rocky or sandy soil can be amended to improve water retention while still allowing good drainage. When amending the soil in a hellstrip, remember that the goal is to create an environment for very tough, very tolerant plants to thrive so that you wind up with a very low maintenance curb garden. If you create a rich and fertile garden environment instead, and use plants that require such an environment, you will spend a fair amount of time out on the street tending your garden. Your plants will probably not be tough enough to stand up to the dogs and kids and cars and snowplows and salt that will repeatedly assault your garden. So save the rich gardening for the backyard, and stick with the hellstrip plan – dry infertile soil and tough plants that love neglect!
Research the types of plants you would like to use to determine how to amend your soil. Certain plants will prefer nothing but good drainage, in which case simply loosening the soil or digging in gravel may be enough. Compost, shredded dry leaves, or sphagnum peat can help water retention in sandy soils. Do NOT add sand to clay soil, the result is concrete! Instead add gravel, perlite or vermiculite, and perhaps some peat or compost .
Xeriscape plants can grow almost literally in rock.
Succulents prefer dry and infertile soil and have shallow roots
Drought tolerant plants prefer good drainage with very low fertility
Bulbs can do well with very limited fertility but like spring rain
Prairie plants and native plants are drought tolerant and adaptable, often spreading or reproducing rapidly
Perennial ornamental grasses or native grasses do well in low fertility with good drainage
Regions with wet summers can expand their plant list from drought tolerant, but your soil may need additional amendments such as compost and garden soil to add nutrients
If you are in an area with heavy winter snowfalls you will probably also be dealing with salt and deicers that get plowed or sprayed up into your boulevard. Your plant selections should be salt lovers or salt tolerant, depending on the amount of aerial and soil salts you are dealing with.