Early Spring Greenhouse Prep
For some growers in North America, the greenhouse season has just arrived (or for some, it never actually ended) and it's time to get prepared for the crop season to come. Below is a basic greenhouse checklist that we hope will give you some inspiration for getting into the growing groove.
Clean and disinfect (everything)
As you know, good hygiene goes a long way towards preventing the spread of disease. In organic seedling production, this is especially important as no conventional fungicides, herbicides, or pesticides can be used to control unwanted infestations. First, start with the greenhouse itself. If the plastic has survived several seasons, a good washing of the interior of the plastic with soap and water can not only reduce spores and pollen that may have gotten trapped throughout last year's production season, but it can also help the greenhouse perform better by allowing more light to reach your trays or soil blocks. Any weeds or plants that may have have been left over from the previous season should be discarded just in case they are harboring unwanted pests or diseases. Exposed soil should be raked of debris and rock or cement floors should be swept. Washing tables also helps reduce the spread of infectious materials.
Sterilizing watering wands, transplant trays, pots, and any other propagation tools is essential. Starting with totally organized and cleaned equipment will give your seedlings the best chance for success. While some growers use a heavily diluted bleach solution to achieve sterilization, other growers have had lots of success using hydrogen peroxide. Either way, tools, trays, and supplies should be washed with soapy water, allowed to dry, and then treated with your preferred disinfectant solution. Similarly, old soils used in previous seasons can harbor infectious materials and should be thrown into the compost. A thin sprinkling of diatomaceous earth over the cleaned area can give your seedling zone one last level of defense against pests.
Check plastic/structural integrity
When it comes to greenhouse costs, heating in early spring can be a big expense. Whether you are using gas, chopped wood, electricity, or wood pellets, making sure that your greenhouse is tightly secured goes a long way to keeping your costs down and lowering your resource usage. Examine your greenhouse for scratches, leaks, and holes--especially around door frames, vents, and fans. Caulk door frames and other structural leakage points and replace plastic where serious damage has been done. Use greenhouse tape for minor rips and tears. Check vents to make sure that they are properly closed shut. Make sure that any repair work is done and totally secure before your seeds get sown.
Controlling the temperature of your greenhouse is an essential part of having successful germination and plant growth. Trialing your heating devices before the season starts can ensure that your first sowings get started on the right foot. Sometimes partitioning your greenhouse space into smaller compartments can help with lowering heating costs. As the season warms, it will quickly become a priority to cool the greenhouse down and move air on sunny days. Making sure that vents, fans, and belts are all functioning properly before it gets hot will ensure that your crops are not impacted by major fluctuations in temperature.
Check Irrigation lines
Whether you've invested in a high tech or low tech irrigation system, flushing lines, fertilizer injectors, dripper heads, and holding tanks can help reduce the spread of disease. Checking the system for holes, tears, breakages, and clogs before seedlings hit the tables can ensure that once your seeds are ready to germinate, the watering system will be primed to keep them growing. Holding tanks and reservoirs that are not cleaned can provide habitat for unwanted algae and insect larvae such as gnats and mosquitoes. Letting the system run after components are scrubbed can flush away unwanted biological materials and clean the system of built up residues, dusts, and pollen. Even if your irrigation is reliant on a handheld hose, checking the hose to make sure it is properly cleaned and functioning before the season gets underway can take the annoyance out of unexpected leakages and problems when you go to water in your first crops.
Crop Plan makes the greenhouse plan
You likely spend hours upon hours pouring over spreadsheets, seed catalogs, and farm maps trying to narrow in on the perfect crop plan for your farm, but how much time do you dedicate to your greenhouse plan? The timing of sowings, potting up, and hardening off all factor into the flow of your greenhouse space. Along with your overall crop plan, it can be good to set aside time to map out how the greenhouse space will be utilized. How many trays will you have? How many trays will be added with each new sowing succession? As plants mature, how will they be moved and eventually transferred outside to harden off? Do you have a special space reserved for microgreen production? The more tuned into the flow of the season you can get on all levels of the farm, the less hassle awaits you during the chaos of the season.
Organize your supplies
For all the A students out there, your supplies were organized in the fall during the winterizing of your farm and this should bring some ease to this new season. For the rest of us, early spring will bring all sorts of opportunities for getting things together before the season speeds up. All of your greenhouse supplies should be cleaned and then organized based on use. Trays, pots, soil block boards, and other plant holders should be put somewhere easy and accessible. Making sure you have enough of each vessel for the season ahead is essential and new materials should be ordered as soon as possible. New potting soil should be placed somewhere that is easy to get to but also out of the way with some form of shade cover to protect the biology in the mix. Any soil amendments, foliar sprays, and added nutrition for the seedlings should be placed somewhere accessible and equally protected from the sun. Seeds should be organized in whatever way works for your growing system, whether it be by crop type or timing, and should be gone through to make sure only new seeds and those that still have good germ remain. Watering cans, spray nozzles, and backpack sprayers should be cleaned and ready to roll.
In the greenhouse, managing moisture fluctuations is a difficult and important task. Plants require water to grow and their very growth contributes to water in the atmosphere. In an enclosed greenhouse setting, this added humidity can contribute to stagnant conditions that promote the spread of disease. Whether you're dealing with the fungal issue of damping off or the water mold issue of phytophthora, good air flow and limited watering will help plants cope with the tropical conditions of your greenhouse. Watering plants with slightly warmed water, especially in the earliest sowings of your season, can help plants cope with the detrimental cold water-loving microorganisms that may inhibit plant growth in the potting soil. Some growers prefer bottom-watering trays to reduce the excess moisture on stems and leaves. Whatever method you choose, you will have to do the dance of watering enough without watering too much, on a daily basis. For more anxious, heavy watering growers, sometimes choosing a lighter potting soil will help give the seedlings the conditions they need to thrive. Opening the greenhouse on especially warm days and running fans will also help reduce the growth of algae on top of potting soil, another symptom of stagnating, humid conditions.
Deal with emerging weeds
As you begin to turn up the heat, dormant seeds will begin to emerge in open soil and in the nooks, crannies, and edges of your greenhouse. Getting on top of sprouting weeds early and often keeps these plants from creating habitat for pests and diseases. It is especially important to ensure that weeds that sprout in these areas are not allowed to go to seed, especially near compost or potting soil getting prepped for seedlings. Grabbing the weeds in the greenhouse is also great preparation for the months of weeding ahead and the small victory of a clean greenhouse can set the tone for a clean field.
Last but not least, it's time to get growing! Starting early crops like onions and leeks is already underway in many states with early brassicas like turnips, radishes, kale, collards, broccoli, and cauliflower coming right up. Before long, it will be time to plan for potatoes and the first of the other nightshades such as peppers, eggplant, and tomatoes and cucurbits like cucumbers will be getting planted into heated tunnels. There's nothing better for the growing season than starting on the right foot and good organization and preparedness early can help kick the season off properly, limiting chaos and staving off the potential for mid-season insanity.