---
title: Greenhouse Winter Checklist & Tips
description: Prepare your greenhouse for winter with our comprehensive checklist and tips to ensure a successful spring growing season. Act now to avoid stress later.
---

[Hummert Blog](https://blog.hummert.com/hummert-blog-home)

# [Greenhouse Winter Checklist & Tips](https://blog.hummert.com/hummert-blog-home/greenhouse-winter-checklist-tips)

 Written by [Gary Pickowitz](https://blog.hummert.com/hummert-blog-home/author/gary-pickowitz) | Dec 16, 2025 3:44:10 PM

 

Winter is almost here! The holidays are ahead and a much deserved break is drawing near. Prior to that break- just a bit of extra work, if not  already taken care of, will help eliminate some of the stresses prior to and during the next growing season.

#### Setting the stage for spring production and a successful spring fundraiser.

Hopefully your plants and supplies are already ordered and confirmed. If they aren’t, please act quickly as logistics, inventory and weather all complicate even the best laid of plans. We always advise shipping supplies in November or December so, if back-orders exist, there is still ample time to receive everything prior to your plants arriving. You don’t want plants showing up before your growing supplies!

Plant orders should be placed as well. Waiting until after the holidays puts you at risk of not getting what you want, as almost all plants are subject to availability from the breeding stations in Central and South America, as well as lead times for the sowing/sticking of bare root cuttings, which can be anywhere from five to ten weeks, depending on the plant. There is still time to place these orders, so act now!

#### Soil:

Can you use last year’s soil? Probably not, especially if it is from last spring. If your soil was received later in the year, chances are that it is probably good to use. Wetting agents are typically good for at least 6 months after soil is received. Depending on the manufacturing date, it may be good for up to a year. After that, the ability for it to absorb water evenly throughout the mix lessens to where the mix will actually repel water. If you use an organic mix this timeline is even less due to the organic nature of the wetting agent which is  
usually yucca extract.  
To easily find out if your existing soil is still good you can try this easy test. Take a handful of dry potting soil  
and place it in a bucket of water. If the dry soil has not taken moisture within a few minutes and is still  
floating on top, your soil mix will cause you problems, and is not good to use. If it darkens with absorbed moisture it should be  
good to use.  
This is a good reason to buy just the soil needed for the next 6 months. If you buy too much and use off of the  
pile during the course of the year, you risk this wetting agent going bad.

#### Quick Greenhouse Checklist:

- Your shade-cloth should be off of the greenhouse. You’ll need as much light as possible reaching your plants  
  well into the month of March. Snow can accumulate on the shade-cloth as well, putting extra weight on  
  your greenhouse structure. Plants usually fare better without shade until sometime in the month of April.  
  This can vary by the type of greenhouse, crops grown, region, etc.
- Check your irrigation system and controls if you have them. Clean filter, check all emitters. It’s a good  
  idea to have an extra solenoid on hand if your system uses them.
- Check your environmental control system to make sure all louvers, heaters, fans and equipment work as  
  they’re supposed to. Make sure you know what your day and night-time temperature parameters are set  
  to and adjust to your needs, these are key to growing a good spring crop.
- Make sure you have HAF fans to circulate greenhouse air. They should be operational and oriented  
  correctly. They push air throughout the greenhouse in a rotating pattern. The importance of these fans is  
  often overlooked. They destratify air layers, help prevent foliar diseases, during daylight hours, and will  
  help your plants grow by moving air away from the leaves that has been depleted of carbon dioxide  
  during photosynthesis. This air will then be replaced with fresh air that has a higher carbon dioxide  
  content. Thus running these fans both day and night is a good practice unless your ventilation fans are  
  on. Rarely can you achieve too much air movement, so more is almost always better.

#### Crop Scheduling:

It’s important to make sure your plants are the size you want for spring sale.

- For hanging baskets bring in plants from the middle to end of February and use four plants per 10”  
  basket for the best quality. Five to 6 plants do well in a 12” basket.
- For 4” and 4.5” pots, schedule for the first week in March and use one rooted liner per pot.
- For bedding flats, schedule plugs for the 3rd week in March.
- Many variables may affect this schedule such as your region, date of sale, market, and growing  
  conditions. The above schedule works best for the Mid-west including the states of Missouri, Kansas,  
  Indiana, Nebraska, etc.
- The ultimate goal is to avoid too small or overgrown plants at the time of your sale.

#### Bugs! They're always a concern:

- Bugs are not here because they’re easy to kill. They’re resilient, adaptive, often bullet-proof creatures  
  that will be with us forever.
- Prevention and early detection are best in preventing problems. Yellow Sticky cards and routine  
  monitoring go far in detecting these pests before they become an issue.
- Check under leaves and on new plant material especially on the newest growth. Most growers ship clean  
  plant material but some harvest off of their own stock plants which can harbor such pests.
- Avoid overwintering pet plants such as outdoor tropical hibiscus, palms and other ornamental plants. If your  
  principal wants a winter home for their hibiscus, please advise against it. These plants harbor  
  just about any kind of insect/mite/pest you can imagine. They are not really visible outdoors, but once brought  
  into the utopian greenhouse environment they’ll manifest themselves and spread, potentially to everything in  
  your greenhouse.
- If you have stock plants that you use for class projects, propagation, etc., please monitor carefully and  
  routinely.
- No weeds should be in the greenhouse. These are also sources of all kinds of insect pests.
- Remove any algae or peat moss on walkways, along the edges of the greenhouse or in the gravel. This is  
  very attractive to fungus gnats that will lay eggs in this media causing flying gnats in short order. Top-dress with fresh gravel to avoid this. If you have concrete floors, this shouldn’t be a concern.
- Consider beneficial insects. They are available now in smaller quantities and make for a great class  
  project. While conventional chemical controls do have their place, this would be a much easier/safer  
  option in the school setting, especially with food crops and students in the greenhouse.

#### Fertilizer:

- Spring crops are short term so it is best to keep your fertilizer regimen simple.
- In most cases, the general purpose 20-10-20 is best with all peat based soil mixes. It  
  is a formation made for growing where the often used 20-20-20 is useful primarily for maintenance.  
  Some growers still use this but better results have been seen with the 20-10-20.
- Fertilizing is best to apply with each irrigation at about 200 PPM if possible. This may not be possible for  
  all but it is much better to fertilize often as these plants are hungry and will develop much better with  
  frequent/adequate nutrition.
- Do not fertilize if dry. The salts in the fertilizer can injure dehydrated roots, causing leaf edge burn....or  
  worse.

#### pH:

- If using a good fertilizer there are typically few pH issues with spring annuals, since their crop time is  
  relatively short. Most fertilizers acidify the irrigation water, which along with the soil pH of about 5.9, will  
  keep the soil pH in the normal range for most plants. This reinforces the argument for fertilizing with each  
  irrigation. Soil pH tends to drift up with most municipal waters that are typically very alkaline. Once that  
  pH gets near 6.8, problems may develop.
- Calibrachoas and petunias the first to show symptoms of this pH drift. They’re very sensitive to the  
  diminished uptake of iron caused by high pH. They serve as that “canary in the goldmine” indicating a  
  looming problem for other plants if not soon corrected.
- This pH topic can be quite complicated but fortunately proper greenhouse practices can avoid most  
  problems that may develop before becoming a real issue.
- A pH meter to keep an eye on your soil, as well as an EC meter which will help you with your fertilizer  
  rates, are good investments to make. This routine testing is a great project also for the  
  students to take part in.

###### Disclaimer:

If you’re doing something different in your greenhouse than what is shared above, and all is going well, please  
don’t change anything. Perhaps modify, experiment and consider, but be cautious before changing a good thing.  
Successful growing is the result of many, many variables. Some we have control over and some we don’t.  
The above is only meant as a guide or checklist prior to the upcoming growing season.  
Questions/Concerns? If you need help or elaboration on any of the above topics, please feel free to contact us. If you need a  
source for or advice on annuals, perennials, pH or EC meters, soil or anything else, we can help you with  
that as well!

Wishing you all a great holiday season!

 

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