The U.S. military is always looking for newer, better, stealthier spies. Its newest recruits in covert missions? Bioengineered plants.

The U.S. Defense Advanced Research Projects Agency announced last month that it has launched the Advanced Plant Technologies program, a “synthetic biology” project that uses actual foliage as surveillance agents. The new program would genetically alter plants’ genetic code to sense and react to predetermined triggers and bioweapons. “DARPA’s vision for APT is to harness plants’ natural mechanisms for sensing and responding to environmental stimuli,” the agency notes in a press release, “and extend them to detect the presence of certain chemicals, pathogens, radiation, and even electromagnetic signals.”

“Plants are highly attuned to their environments and naturally manifest physiological responses to basic stimuli such as light and temperature, but also in some cases to touch, chemicals, pests, and pathogens,” APT program manager Blake Bextine said in a statement. “Emerging molecular and modeling techniques may make it possible to reprogram these detection and reporting capabilities for a wide range of stimuli, which would not only open up new intelligence streams, but also reduce the personnel risks and costs associated with traditional sensors.”

Under this new initiative, plants are being enlisted as “the next generation of intelligence gatherers.” The agency reports it already has the “ground-, air- and space-based technology to remotely monitor… plants’ temperature, chemical composition, reflectance, and body plan, among other qualities.” The resulting plants can therefore be carefully observed, and any changes will serve to immediately alert federal authorities when particular stimuli are present. Beyond U.S. military use, the agency suggests that the technology could be used to find, and ultimately clear, long-buried landmines and other unexploded ordnance.

This isn’t the first time greenery has been tasked with security duties. Last year, researchers at MIT announced they had “transformed spinach plants into sensors that can detect explosives and wirelessly relay that information to a handheld device similar to a smartphone.” Colorado State University biologist June Medford has developed plants that change colors to warn of airborne pollutants, toxins and explosives. Another DARPA project Medford leads aims to someday replace airport security checkpoints with gardens full of genetically manipulated plants that can detect drugs and bombs.

Plants are complex entities, and futzing with their basic biology to create trained surveillance and security agents is painstaking work. DARPA’s similar previous experiments haven’t gone well because gene edits “reduced the fitness of modified plants by siphoning resources needed to sustain the plants.” A key component of the APT program will be determining how to fix that, so plants actually live and thrive after they’ve been tinkered with. The agency plans to “improve how plants collect and distribute resources, and optimize their fitness” so that the engineered plants it uses can flourish despite dealing with “natural stressors such as microbes, animals, insects, and other plants.”

DARPA’s expressed intent with the ATP project sounds efficient and even fascinating. But every new tool in the government’s surveillance toolkit elicits some concern about mission creep: the tendency for military efforts to grow beyond their initially identified scope. What else could plants that are genetically engineered to identify and rat people out do? In a decade, how wary will you have to be of the vine growing along your window shutter? It may sound paranoid, but history shows us that mission creep is very real. The agency promises to “adhere to all applicable federal regulations with additional oversight from institutional biosafety committees.”

That means, at least for now, all plants remain innocent and trustworthy.