Greenhouse Management

February surprises me each year with feelings of doubt.  As the days grow longer and the boxes of seeds are unpacked and organized for the seeding marathon that lies ahead, I feel a tremor inside of me.  Really? I think, as I stare at all of the seeds. Will these really turn into enough food for hundreds of people?  I look at the small bags of carrot seeds, and then I poke my head into our walk-in cooler, which still has over 6,000 pounds of stored carrots in it.  I look back at the carrot seeds.  Impossible.  There’s no way these seeds will turn into that heavy pile of food.

As the month progresses, the self-doubt grows into action, which gradually blooms into tentative excitement.  There is suddenly so much to do in these few short weeks – and there is so much personal fun to cram in there as well before all of my freedom evaporates into full-fledged farming.  Have I caught up with all the friends and family I vowed to this winter?  Have I skied enough powder to make up for all of the swims and bike rides I won’t get to do this summer?  Have I read enough novels to tide my brain through the summer?

Then March hits.  The greenhouse fuel corn arrives and is ignited.   Heat mats are rolled out, the first tomatoes are seeded, and onion flats are filled.  And the minute the first seedlings pop their crooked, dull green elbows out of the soil, all of my doubt explodes into sheer amazement.  Seeds and soil and light and water become food.  That’s all there is to this: it just takes organization, patience, energy and the ability to learn year after year after year how to do things just a little bit better.

At the Intervale Community Farm, we grow seedlings in our greenhouse for a 540-member summer CSA and a 170-member winter CSA.  Little by little, we’ve improved our seedling and transplant production and our ability to get the work done more efficiently.  We still have so much to learn and improve, but here are a few simple strategies we use to produce healthy, organic transplants for our farm.

 

Creating a Greenhouse Plan

Winter affords us the luxury of time to plan and think about our farm systems.  And in the farm season, my brain is a sieve for these details.  I try to take advantage of the winter to create as bullet-proof a greenhouse plan as possible – both for me as a reference and for our staff to use independently.

Our farm uses linked excel spreadsheets for our entire crop planning, and that has worked well for us.  However, there are several resources that provide crop planning templates, including:

Finding the program that works for your operation is key; but having a solid plan is essential in easing the spring seeding stress.   Here’s an example of the greenhouse plan that we use on our farm.  This plan is an Excel spreadsheet that is linked to all of our other field plans and seed ordering information with formulas embedded in most of the cells, which makes year-to-year changes easy to implement:

 

Tray Selection

Finding the right trays for your greenhouse operation is important in tailoring your system so it works for you.  At ICF, we’ve loved the reusable 150-cell Plastomer trays, which unfortunately are not currently available (to our knowledge).  We also rely on a supply of reusable Winstrip trays which are also difficult to source.  Other high quality, reusable tray options that are easier to find are Proptek and Plantel trays.

Many growers use soil block makers, which produce high-quality transplants and don’t require any use of plastic.  Soil blocks use more potting soil and would be difficult to handle with the systems our farm already has in place – but they are a wonderful alternative to plastic seeding trays.

Regardless of what system you choose to start your transplants in, the most important things to consider are the physiological needs of each type of transplant, the cost and labor efficiencies associated with different size seedling trays, and how the tray style fits into the rest of your farming system.

Seeding

A determining factor in our tray selection is our seeding method.  At ICF, we use a GRO*MOR Wand Seeder with a single wand that was fabricated specifically for our 150-cell trays.  We’d increase our efficiency if we upgraded to an E-Z Vacuum Seeder, and it is a likely investment our farm will make in the next few years.  On the smaller end of the scale, are GRO-MOR Vibro Hand Seeders and Hand Seeder Sower. And of course, there is the tried and true method of using your fingers to place the seeds in the seeding tray, which our farm does for many crops that we seed a smaller quantity of.

One of the most important factors in our operation for consistent germination is having the flats filled evenly. It makes a tremendous difference to have the soil filled in the cell trays with a gentle firmness to it.  If the soil is too fluffy, the seed might get pushed in too deep, it may not receive adequate light, it can get pushed around by loose potting soil, or may suffer from water pooling around it.  It’s worth taking the extra time to fill flats properly and not skimping on potting soil.

Watering

This entire article could be devoted to the art of greenhouse watering, but the resonating point for me is that it’s essential to designate one responsible, knowledgeable person to water.  Having one person always watering will ensure that there is an attentive set of eyes on the plants.  This person also doubles as a pest and disease scout and a person who will alert you to the transplants that are ready to go to the field.  Many growers (including myself) like to self-designate as the primary waterer.  I love this task because it gives me a steady awareness of the health of the greenhouse while it also forces me to slow down – because watering is one thing that you just can’t hurry.

Cornerstone watering principles:

  • Pay attention to the forecast and water accordingly.  Most importantly, if there are a cloudy days in the forecast, water as little as possible.  The plants aren’t using much water in this weather, and you can foster fungal diseases by creating a constantly moist environment around the plants.
  • Use a hose trolley to keep your hose off of the ground. This can help prevent the spread of diseases – and means you’ll be less annoyed by snaking around a hose.  Trolleys are easy to build yourself, or you can order a prefab one.
  • Pay special attention to the edges of the trays. These dry out quickly and often suffer from lower germination rates and slower growth than the rest of the tray.  It’s especially important to water the edge along the greenhouse wall.  I try to get the hose directly over the trays so that the spray is perpendicular rather than angled.  This serves two purposes: it prevents soil from splashing around and forces me to focus on watering each space thoroughly.
  • Trust your instincts.  Because I water every day, I know which plants need more or less water and which trays tend to dry our quicker than others.  These intuitions guide my watering practice and allow me ways to quickly assess what is happening in the greenhouse.
  • Pay attention to the quality of your water.  The pH, alkalinity and temperature of your greenhouse water can affect your seedlings, especially more sensitive crops like flowers and bedding plants.  It’s worth having a water test done each year to know what you are spraying on your plants.   For more information, visit the UMASS extension fact sheet or talk to your own local extension for guidance.

For more tips on watering, you can read Paul’s Guide for Watering in a Greenhouse.

Sanitation

My approach to greenhouse management and sanitation has evolved as I’ve understood that running an organic farm does not mean that when left alone, good organisms will triumph.  I once thought that the cycles of freezing and summer heat were enough in our Vermont climate to conquer most greenhouse diseases and pests; but after years of repeated disease problems, I’ve slowly understood how carefully we must pay attention to what diseases and pests are present and manage accordingly.

One key management practice is to prevent soil-borne diseases from carrying over from year to year.  Because we reuse most of our greenhouse trays each season, we make sure to clean them before the new season starts.  We use a power washer to blast away old potting soil and then we dip the trays in a sanitizer solution (we use Oxidate).

Within the greenhouse, it’s important to constantly remove all plant debris, soil piles, weeds, and to make sure that you don’t have water pooling or collecting anywhere in your greenhouse.  All of these things can incubate and harbor pests and diseases.  In addition, it would be ideal to annually sanitize the greenhouse benches, doors, baseboards, etc.  Last year, I scrubbed our garage doors free of the green algae scum that has been collecting there for several years and it was both satisfying and horrifying to remove the layers of scum.  I vowed to make this an annual task – and found myself wondering how much of our algae problems in the greenhouse were related to these scummy doors!

Most vegetable growers are not full-time greenhouse managers, so creating a priority list of greenhouse cleanliness tasks might help:

 

Pest and Disease Scouting

There are loads of amazing resources available to growers for pest and disease scouting.  Even if you can’t tell an aphid from a white fly, it’s worth putting out sticky cards in your greenhouse to trap the pests that might be around.  It’s fun to take a crack at identifying the insects, but it’s also really easy to ask your local extension for assistance.

Here are a few simple scouting principles:

  • Designate a time each week when you take a look around your greenhouse looking for problems and checking your sticky cards.
  • Remove ANY plants from the greenhouse that alarm you because they are diseased or infested.  Ideally, you’d get each problem diagnosed, but this might be cost or time prohibitive, so use your judgment on what you can or can’t tolerate.
  • Use your resources.  UVM, UNH, UMAINE, and UMASS are a few here in New England that all have excellent support for greenhouse pest management.  There is a wonderful annual greenhouse IPM workshop offered in Vermont, New Hampshire, and Maine.
  • There are also companies like IPM Labs and Biobest that sell beneficial insects to help combat greenhouse pests.  These companies are also great resources for any questions you have regards pests.
  • Use the outdoors to your advantage.  When I have a problem that I don’t have time or energy to deal with the moment I notice it, I just move the problem plants outside (weather permitting).  This allows natural enemies and the flow of fresh air to perhaps alleviate the problem – but most importantly, it protects all the other plants from infection.

Greenhouse flow and layout

Like most vegetable farms, we always manage to max out our greenhouse space, particularly if we have a late spring and can’t get into the field in a timely fashion.  One thing we try to think about early in the spring is how to move around our trays as few times as possible for efficiency.  When we finish seeding or transplanting trays, we think about placing seeded flats in the right region of the greenhouse based on watering needs and the temperature needs of that crop.  We also consider what is going to be moved out into the field soonest.  And most importantly, we label each tray clearly because you never know who might be reaching for a tray to plant in a few weeks.  But despite our best efforts, there never fails to be a hot pepper/ sweet pepper surprise in August!

February is a month of checklists, of making sure everything is lined up for a smooth and organized season ahead.  It’s impossible to think of everything, and it’s even less possible to prepare for the inevitable farm unknowns.  The best we can do is to arm ourselves with a sturdy plan, an open-mind, a desire to learn, a passion for the work, and with a winter-rested mind and body.  With the right preparation, the doubt of February quickly becomes the confidence of March!

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8 Responses to Greenhouse Management

  1. Peter J DeLuca says:

    Great work thank you so much….

  2. Silvia says:

    Great blog post.

  3. David Martin says:

    Such an insiteful essay. My operation is much smaller, only starting about 40 flat of veggies and flowers for personal use,Yet its nice to know that someone as professional as Becky would share her experiance with us little folks to use and enjoy. Thanks

  4. Maire says:

    wow- great work. I envy you for being able to do this. We are in survival mode, ourselves- and have no money or resources to do this. Wonderful to see someone who can do it.

  5. Matt says:

    Great post! Thanks so much for the info. I’m on the hunt for standard temperatures for day and night for veggie transplants in greenhouses. I have figured a few things out by trial and error over the years, but would love to find a resource of tested norms for various plants. Any ideas? What do you guys use for onions, solanums etc. ?

    Thanks again! Matt

  6. Maggie says:

    Great article. I’m looking forward to implementing some of your suggestions in my greenhouse. I’ve been having a bit of an aphid issue and am defiantly going to give some plants to boot today. Cheers!

  7. Rebecca says:

    From one pro to another, I like your article. I especially like your comments on the importance of one person being in charge of water, and keeping hose up from ground. Your comments on reusing flats and pressure washing them is great…something I haven’t thought of doing. I just tossed the yucky ones and saved the unfunky ones. Thanks!

  8. Lynda says:

    Great article, Becky. Technically astute and practical. It’s great that you are sharing your experience.

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