Finishing up 2023

Monday, November 27, 2023

 As we finish up our 2023 growing seasons, it is time to re-visit our standard cleaning procedures. Throwing out the old and preparing for the new is one of the most important components to protected production.

While this is going to look different for those in soil-based systems compared to those who are set up hydroponically, there are some key practices that can be adapted to any protected space:

  1. Removing ALL organic matter from the greenhouse, and greenhouse vicinity
    • dried up leaves, old soil, dirty pots and growing supplies are perfect hiding spots for pests and disease to overwinter. Its important that you eliminate as much potential habitat and food source as possible
    • Don't hesitate to do this in stages. Clean out the big stuff, and come back a second and third time to get rid of the bits and pieces that were not picked up the first few times. 
    • Do not leave piles of plant material or old soil next to your greenhouse. As much as these serve as habits inside the production space, they will do the exact same thing outside. No matter how well the inside is cleaned, if you have a major source of insects just steps away from the greenhouse...there will be problems
  2. Collect all old growing supplies from the year, and remove from the space for cleaning. Pots, carrier trays, pruners, clips, support stakes/string etc. should be dealt with to reduce pathogen and pest load into the new production cycle. Pots, carrier trays and pruners can all be sterilized and re-used, but be aware of the cleaning agent used here - some are going to cause more harm than good! Wooden stakes, while tempting to re-use these, cannot properly be sterilized because they are highly porous. Disease transfer from year to year from re-using stakes is possible.
  3. Consider swapping out ground cover if you are using something more substantial than plastic mulch! While this isn't something typically tackled on a yearly basis, following a heavy disease year it can be worth considering getting a new cover put over the ground. If you are considering this, remove the old cover before going forward with suds and sanitizer! That way your ground layer will be scrubbed back to a base layer of clean, and you can be confident that nothing is hiding out in tiny cracks and crevices throughout the old ground cover.
  4. Lets get soapy!
    • Giving all growing surfaces a soapy scrub is going to grab hold of any bacterial, viral and fungal agents that are still in the space and wash them away. 
    • The best strategy for washing a greenhouse is to start at the top and work down - and this includes your ceiling! Failure to wash the top of the grow space creates a disease bank that can literally rain down on your future crop.
    • Once you have applied your soap, give the production space a thorough rinse and allow it to air dry
  5. Once you have allowed the space to airdry after cleaning, it is time to bring in the big guns- Sanitizer! There are a lot of sanitizers on the market to chose from, but they do have a few things in common:
    • Contact time is important. Different products have different required contact times in order to be effective. Be sure to check what the required contact time is for your product of choice, and do your best to adhere by that. Otherwise there is no guarantee that the product will sterilize to the degree that you are hoping for
    • Organic matter will de-activate sterilizing agents. Any of those leaves or soil bits that got left behind in pots and seeding trays will actually render your product useless. 
    • Consider how corrosive your cleaning agent is. Bleach is effective, but does impact the longevity of growing equipment, both for plastics and other materials.
    • TEMPERATURE. Sanitizer efficacies significantly decrease at lower temperatures. While it is difficult to justify heating a protected space for cleanout, it is a key factor in maximizing your product efficacy.

Here are a few other considerations for your end-of season wrap-up:

-Once the production space and tools have been cleaned, be conscious of what is coming into the space. Just because you aren't actively growing plants, doesn't mean you are immune to accidental spread! Clean clothes/shoes/growing supplies should be the only thing that enter the space for as long as possible to maintain the clean slate.

-For those who are growing in soil, producers should consider removing plastic on spaces that are not being used for production. The lack of rainwater coming onto your tunnel soils will result in the accumulation of salts in the soil. One of the best ways to tackle this is to allow the snow and rain that come with the winter to run through the soil. Come growing season, this will allow for better uptake and use of supplemented nutrients, and less stress caused by buildup over time. Plastic removal can be a pain, so even doing so every few years is going to be hugely beneficial. For more information on soil salinity in high tunnels, check out this fact sheet!

-Looking to maximize the performance of over-wintered cover crops? Unheated, double poly inflated greenhouses are not going to give enough protection from those cold winter nights. The addition of one or two layers of ground cover can work wonders for your cover crop, reducing large fluctuations in temperature and buffering against cold snaps. It also helps to protect soil moisture for your cover crop. As our day lengths turn around, these plants will see a huge boost in productivity in February and March, increasing the amount of in-house biomass generated to be worked back into the soil before bringing in the cash crop. 

Row cover is best installed after a cold snap or two in the greenhouse space. This should function to kill some of the pests that may still residing in the space, before adding the additional layer of protection

Here's to a fresh start!

Posted by: Talia Plaskett