Weeds are simply plants out of place, and not all need to be removed. When deciding a weed’s fate, a gardener must consider, among other factors, the weed species, its location within the garden, and the weed’s potential function for its location.

We are taught a garden should be weed-free and that each weed not pulled is a mark against us. In the United States, gardeners spend millions of dollars and millions of hours annually pulling, digging, cutting, spraying, smashing, cursing, hacking, and otherwise declaring all-out war against weeds in their gardens and lawns.

Weeds are plants out of place. This means that the dandelion and the tulip alike could be considered a weed depending on where they grow, how they grow, and the gardener’s tolerance for them in that location.

Gardeners should keep in mind that weeds are simply plants out of place, and that weed species in certain places can be acceptable (and maybe even beneficial).

When a plant is growing in an unplanned place we cannot ask, in absolute terms, “Is this a weed or a flower?”, eliminate those falling in the former category, and still have a sustainable or ecologically-informed approach to gardening. Determining if a weed is worth removing involves more than a simple ‘good’ or ‘bad’ categorization. The gardener must consider, among other factors, the weed species itself, the weed’s location within the garden, and the weed’s potential function for its location in the garden.

Lipidium campestre (pepperweed) is a common weed of most gardens, including Lurie Garden. Most prevalent at Lurie Garden in the spring, pepperweed is pulled whenever possible but most are quickly shaded out by surrounding ornamental plants as the growing season progresses. Here, L. campestre is seen among a field of the desireable Muscari armeniacum ‘Superstar’ (grape hyacinth) at Lurie Garden.

Lurie Garden’s Categories of Weeds

Instead of discussing weeds as good or bad, Lurie Garden considers weed species as another part of the garden to be managed. Just as we manage the location and appearance of Echinacea pallida (pale purple coneflower), staff also manages Taxacum officinale (dandelion). At Lurie Garden, weeds fall into the following four categories:

• Plants we never like
• Plants we once liked but are now hard to control
• Plants we leave and use in the garden
• Plants that disturb the design

Even these categories are not absolute. While garden staff and volunteers may remove certain weed species from one area of the perennial planting beds, the same weed may be left elsewhere in the garden because it serves a specific horticultural or ecological purpose in that location. Gardeners should keep in mind that weeds are simply plants out of place, and that weed species in certain places can be acceptable (and maybe even beneficial).

Plants We Never Like

There are certain weed species our horticulturalists and hands-on volunteers never like to see and are religious about removing from the garden. These weeds are aggressive, invasive, and considered noxious. Convolvulus arvensis (bindweed) is a member of the large, taxonomically complex morning glory family (Convolvulaceae). This weed species is a perennial vine that twists its way around upright stems of surrounding plants to reach maximum sunlight exposure. When left unattended, their growth results in large, dense mats of vines that shade-out surrounding plants. The round white flowers of bindweed may look appealing in the garden, but they will go on to produce a multitude of seed to spread this aggressive weed around the garden.

Convolvulus arvensis (bindweed) is seen here growing in Salvia x sylvestris ‘Blue Hill’. Bindweed vines can quickly cover shrubs and other plants, killing them by shading and strangulation. At Lurie Garden, bindweed is controlled by hand-digging.

Lurie Garden staff and volunteers hand dig bindweed plants as they are found in the garden’s perennial beds and shrub planting areas. Bindweed is a deep-rooted plant, so pulling is often ineffective and results in multiple plants arising from broken root segments. Herbicide treatment for bindweed can be effective; however, no synthetic chemicals are used in Lurie Garden for the control of weed species in accordance to the garden’s sustainable and ecologically-informed management philosophy.

Another weed species regularly removed by Lurie Garden is Taxacum officinale (dandelion). Many gardeners battle dandelion in their garden and lawn spaces, so the fact that Lurie Garden removes this weed species from the garden may not be surprising. However, dandelion is removed from the garden not because of aesthetic reasons, but because of the species’ reputation as a heavy seed producer and ability to quickly establish a monoculture that may out-complete more desirable ornamental plants. Lurie Garden appreciates the ecological value of dandelion as a source of pollen for foraging pollinators, but in the specific setting of Lurie Garden, where a particular design is to be maintained, the plant is considered weed species to be controlled.

Taxacum officinale (dandelion) is a common weed in gardens and lawns. Dandelion produces copious seed, which can quickly spread through a garden setting to create a monoculture. This weed species is controlled by hand-digging at Lurie Garden.

Plants that Have Become Difficult to Control

This category of weed at Lurie Garden is comprised of plants most gardeners may not consider as traditional weeds. Many of the plants in the group are perennial plants once installed as part of the garden’s design, but have become too aggressive or ‘weedy’ in the garden and must now be removed. Often they are beautiful plants, but act like real bullies in the garden.

Briza media (quaking grass) is a beautiful ornamental perennial grass originally installed at Lurie Garden; however, the species quickly became an aggressive plant in the garden. As a result, garden horticulturalists classified quaking grass as a weed and continue to remove it from the garden.

Tradescantia (spiderwort) is a New World genus of plants in the Commelinaceae family, with many species native to North America and several cultivars available in the horticultural market. Tradescantia was planted in Lurie Garden as part of the original design plan with hopes plants would naturalize to fill-in bare soil areas. It accomplished this task well – in fact, the plant grew too well in the garden’s setting and began to out-complete surrounding plants. The designers and horticultural staff, using the garden’s ecological approach to management as a guideline, made the decision that Tradescantia must be removed from the garden’s plantings. While large areas of the garden have been cleared of this ornamental species, due to the plants ability to seed-into areas and reproduce by underground rhizomes, plants continue to appear throughout the garden – If any part of the root is not removed, a new plant can grow from the remnants. Each new appearance must be hand-dug to prevent a future appearance.

Tradescantia (spiderwort) is seen here appearing among Monarda brandburiana (Eastern bee balm) and Pycnanthemum muticum (mountain mint). Spiderwort was once a part of the Lurie Garden’s planting design, but due to its weedy tendency was selected to be removed from the garden. The process of removal continues by hand-digging.

Plants We Leave or Use in the Garden

Lurie Garden’s ecologically-informed approach to garden management means that, for some weed species, the time, effort, and soil disturbance required for removal outweighs any damage the weed plants themselves cause in the garden. In fact, many of the weed species in this category may serve beneficial purposes in the garden—attracting local pollinators to the garden or serving as groundcover plants to fill bare soil and prevent more aggressive weeds from establishing.

Oxalis stricta (yellow woodsorrel) is one of the most common weed species found in Lurie Garden. Yellow woodsorrel is not removed from the garden’s planting beds as it acts as a groundcover, helping to keep more aggressive weed species from establishing in the garden.

Oxalis stricta (yellow woodsorrel) is a native North American plant in the Oxalidaceae family. Despite being one of the most ubiquitous weeds in garden and greenhouse settings, several interesting ornamental cultivars of yellow woodsorrel have been developed. At Lurie Garden, yellow woodsorrel is one of the most common weeds encountered throughout the perennial planting beds. Additionally some gardeners may learn to appreciate their lemony-flavored seed capsules as a garnish, making them a very welcome edible weed.

Lurie Garden staff and volunteers rarely bother removing yellow woodsorrel from the garden. This weed species is not only somewhat attractive, but also serves as a worthwhile groundcover to fill bare soil spots that would otherwise become infested with more aggressive weed species. Oxalis stricta is often found growing in combination with Duchesnea indica (mock strawberry), the latter being another common weed species left in the garden to serve as a groundcover.

Duchesnea indica (mock strawberry) is another common groundcover weed in Lurie Garden. As with Oxalis stricta (yellow woodsorrel), mock strawberry is rarely removed from the garden because it serves as a great groundcover plant.

In the early spring, Lurie Garden’s perennial planting beds are often covered with Cardamine hirsuta (bittercress). This annual or biennial member Brassicaceae can be one of the first plants blooming at the garden. We do not remove bittercress due to its prevalence throughout the garden, small size, and pleasant early spring flower. Additionally, this weed species is quickly shaded out by other ornamental perennial plants as the spring growing season progresses.

Cardamine hirsuta (bittercress) is a common early spring weed in Lurie Garden. This weed species is not removed from the garden since it does little harm to the garden, its design, or development.

Plants that Disturb the Design of the Garden

There are some plants that just find themselves growing in the wrong place – Asclepias syriaca (common milkweed) growing in the middle of our iconic Salvia River, for example. In these cases, garden horticulturalists make the decision to remove the ‘weed’ even though the offending plant is actually an ornamental perennial elsewhere in the garden’s design. In the case of plants critical to life-cycles of insects or other animals, out-of-place plants are removed before being used for egg laying or other important life-cycle stages.

An out-of-place Asclepias syriaca (common milkweed) in the garden’s Salvia River (Salvia nemorosa ‘Wesuwe’). Balancing the artistic integrity of the garden’s design with ecologically-informed management, garden’s horticulturalists removed this one common milkweed plant from the Salvia River early in the growing season. Other large colonies of common milkweed, A. incarnata (swamp milkweed), and A. tuberosa (butterfly milkweed) exist elsewhere at Lurie Garden. Even though common milkweed is a part of the garden’s perennial plant design, sometimes a plant out of place can disrupt the artistic intent of garden design elements.

Weed Control at Lurie Garden

How best to control weeds in gardens and lawns is an often hotly debated topic. Each gardener has their preferred weed control method and tool. Weed control does not have a one-size-fits-all solution. Much as the gardener must consider the location, invasive potential, ecological function, and design consideration of a weed to determine if it should be removed; before implementing a weed control method, gardeners must consider personal or professional philosophies and the ecological impact of their preferred control methods.

Lurie Garden uses sustainable and ecologically-informed methods of garden management that attempt to balance the aesthetic requirements of maintaining the artistry of the garden, while simultaneously relying on the resiliency and plasticity of the garden and its biodiversity as an ecosystem.

For weed control, applying this sustainable philosophy means that no synthetic herbicides are used within the garden and alternative methods are used, evaluated, and applied throughout the garden setting. Methods of weed control at Lurie Garden include:

• Hand pulling and digging – Used for most weed species found in the perennial planting areas of the garden.
• Burning – Weeds occurring in the cracks and crevices of the public pathways throughout the garden are burned using a hand-held propane torch.
• Shading – Many early spring weeds occurring in the garden are not pulled or hand-dug because the surrounding perennial plants will, later in the growing season, grow taller than the weed plants, shading them out of the garden.
• Ignoring – Many weed species are simply ignored because they fill bare soil spots throughout the garden and help prevent more aggressive weeds from becoming established.

Ornithogalum umbellatum (garden star-of-Bethlehem) exemplified the struggle of the garden to determine if a plant is a weed or valuable ornamental plant. This native European plant was brought to the United States as an ornamental plant, but soon escaped cultivation and has become a weedy (and even invasive) plant in many gardens and natural areas. At Lurie Garden, garden star-of-Bethlehem is removed from planting beds. What would you do with this plant?

Quick Tips  – Deciding What Weeds to Control

• Learn about the specific plants that start voluntarily growing in your garden. You may learn that the ‘weed’ you have been pulling for many years may actually be beneficial.
• Consider the location, potential function, and invasive potential of a weed before controlling.
• Be proactive, persistent, and thorough in controlling aggressive, invasive, and noxious weeds in your garden.
• Research new plants before installing in your garden. Some ornamental plants may become weeds in your garden setting.
• Weed control is not a one-size fits all scenario. Consider multiple methods of weed control for maximum effectiveness. Aim to work smart not hard.
• Be open to volunteer design surprises. If a controllable plant suddenly appears in an unplanned place, wait to see if it creates a new, desirable effect that you would not have thought of otherwise. You can always remove the plant later.
• ‘Weeds’ can surprise you! Take some time to examine the plant you are about to eliminate. A weed may have an interesting or beautiful character that brings a welcome, unique addition to your garden.

Sonchus (sow thistle) can be a troublesome weed and is often removed from Lurie Garden. Nonetheless, when the perfoliate leaves of sow thistle are examined more closely a certain beauty and interest can be discovered. Who knows, maybe some gardener out there uses Sonchus to bring a hard-edged, industrial look to their garden!

Do you have any stories of an ornamental plant turning hostile in your garden – or any ‘weeds’ you have started to tolerate or allow?

Weed Identification Resources

Two favorite weed identification and control guides for Lurie Garden staff and volunteers are:

• Alexander Martin. 1987. Weeds. St. Martin’s Press – This small format book (only 6 in. x 4 in.) is a good quick-reference guide for the most common weeds found in North America.
• Sally Roth. 2002. Weeds: Friend of foe? The Reader’s Digest Association – This book is both a good identification guide and unique coffee table book to stimulate discussions with gardener and non-gardeners alike.