PLANT GROWTH 101Plant Care

Keep It Clean

By the Hormex team 5 min read

I got an email from a worried man who had a complete failure in his rooting efforts. After successfully rooting a variety of plants, he lifted the hood one day to find disaster. Every cutting in the 2’x 2’ box was flat on the surface of the rooting medium, its stem darkened at its base. His setup sounded good: a deep rigid plastic box with drainage and a removable hood made of PVC pipe covered with sheet plastic. He used a heating mat in winter, always waters with distilled water, and ventilates daily. The box sits on a protected porch in USDA Zone 9, the subtropics, so freezing is not a problem. The list of plants he propagated this way was impressive, too, from succulents and green stemmed tropicals to azaleas. He feared he had lost his touch, but I was able to assure him that no existential crisis loomed. The symptoms could indicate damping-off or root rot. Pythium, a water mold rather than a true fungus, is one possible cause, but the diagnosis was not confirmed.

There are so many fungi on Earth that even mycologists can only estimate the number at about 1.5 million species. When I answer questions about a filmy black deposit on tree leaves in summer, it can be painful to explain that the sooty mold fungus is everywhere. Fungi live where they can find a comfortable host, in this case the excrement from insects feeding higher up in the plant. The pH and sugar content of this ‘honeydew’ is perfect for the sooty mold to land in and grow. It is ubiquitous in the atmosphere of humid climates, but some type of fungus is equally present almost everywhere. We depend on many fungi and try to limit plant pathogens that can damage vulnerable cuttings.

The cause cannot be established from the description alone. Plant pathogens can enter a rooting chamber on contaminated tools, containers, plants, water or media. Sanitation and appropriate moisture management can reduce the risk of another loss, but do not guarantee prevention. Even though I know the drill, so to speak, I learned a thing or two as I answered the question – that’s the way it’s supposed to work after all – and wanted to blog about it.

Without a confirmed diagnosis, the practical next step is to remove affected material and thoroughly clean the propagation setup before starting another batch. Here are some useful sanitation practices:

  • Construct your propagation box or chamber from new materials and avoid wood if possible because it is difficult to keep clean.
  • Use clean, fresh rooting media and keep extra media clean. Why don’t more bags have zipper closures, anyway? Keep bags of media or its components closed tight or even better, put bags into plastic boxes with tight-fitting tops.
  • Love that shop-vac! Keep the area around the rooting chamber clean and dust free to reduce sources of infection and improve air quality for you. If other plants, pots, or soil are nearby, move them.
  • Keep a spray bottle of 70% alcohol handy to disinfect any tools used inside the chamber such as misters or watering cans. Be sure any rags or paper toweling you use is fresh, too.
  • Clean hands, please. Since it is hard to remember, keep hand sanitizer nearby.
  • After each set of clones is rooted and pulled out, clean and disinfect thoroughly.
    • Use fresh rooting medium between batches. Discard affected plants and media away from the propagation area rather than recycling them into other potting mixes.
    • Wash each component of the rooting box or chamber with soapy water, rinse with clear water, and let dry completely.
    • After removing soil and plant debris and washing the parts, use a disinfectant suitable for the material. Follow its label for dilution, required contact time and rinsing. Prepare solutions fresh as directed; there is no universal two-hour expiry rule.
    • Work in a well-ventilated area and wear the protective equipment specified on the label. Never mix bleach or other disinfectants with other cleaners. Keep disinfectants away from plants and growing media. Bleach can corrode metal, so choose a suitable product for tools and follow the label and equipment-care instructions.
    • Use new pots and sheet plastic for each new set of clones. Yes, you can clean them, but besides the rooting media itself, these are the greatest potential sources of contamination.

One more note: Professional products to disinfect include quaternary ammonium compounds (Green-Shield), hydrogen dioxide (Zero Tol 2.0), hydrogen peroxide compounds (Sanidate) and others. When you make the move from backyard propagator to professional and/or greatly increase the size of your propagation operation, consider them. Some organic disinfectants are available; consult product labels and omri.org for details and keep abreast of local restrictions if you are cloning for the organic market.

The post Keep It Clean appeared first on Hormex for Plants.

Further guidance: University of Minnesota Extension on cleaning garden tools and containers and CDC guidance on using bleach safely.