Weekly Green Tip: How Plants Compete ☘️🌱

Plants, though rooted in place, are constantly in the midst of competition and their own forms of communication. Sometimes, these interactions can be predicted. Here are some small considerations with competition in the garden…

 

“AGGRESSION” IN THE GARDENING SENSE

The word “aggressive” inherently can have a negative connotation, so in the gardening sense, it is somewhat of a jargon speedbump to get over. Some of our most valuable native plants are considered aggressive, but they still deserve a place in our landscapes! Don’t exclude them! Instead, be strategic in how you incorporate them.

An aggressive plant may be something spreading underground through brazen rhizomes or something extraordinarily efficient at self-seeding. For the former, many folks containerize rhizome spreaders and for the latter, some may deadhead their plants to limit the seed dispersal. If you’d like a seemingly more natural route, consider planting aggressive species together so they compete on an even playing field. Another option is being diligent in giving aggressive plants ample space to spread and thrive unimpeded!

Let’s make a scenario for us to consider… take the mighty goldenrod! It offers habitat to the widest diversity of pollinator species in our region BUT it is an aggressive spreader by both seed and rhizome. Rather than exclude this powerhouse of a plant, why not give it an ample, designated area in the landscape OR plant it with other similarly aggressive plants like joe-pye weed, asters, or cut-leaf coneflower (to name a few). 

In the eastern temperate forest eco region, over 100 pollinator species use goldenrod as a host plant (laying eggs, developing caterpillars) and over 40 pollinator species rely on it for pollen. 

ALLELOPATHY

Allelopathy involves plants releasing chemicals that can hinder (or sometimes assist) growth of other nearby species. These plants can curate who their neighbors are, which in turn can give them an inherent advantage in their environment. Landscapers sometimes use these plants tactically to suppress understory growth and therefore limit maintenance.

Here are some common ones you may see around — some of these should be an instant pull (in our opinion) and others you should consider strategizing around:

Black walnut — This tree is well-known for producing juglone, a chemical that can inhibit the growth of many plants, including tomatoes, potatoes, and azaleas. It is a fantastic, native, overstory tree — but if you have one, be careful planting in its vicinity.

Common Sunflower — This extraordinarily pretty, native flower tends to inhibit growth of many different species. Be strategic when planting these!

Eucalyptus — A commonly found non-native tree here in Atlanta, known for its exotic look and aromatic leaves. Eucalyptus releases allelochemicals that can suppress the growth of understory plants.

Tree of Heaven — Quite the misnomer for our region! Not only is this tree highly invasive, but it also releases chemicals that can significantly inhibit the growth of other plants. If you find this on your property, do yourself a service and dig it up- don’t just cut it back!