Transferring your transplants from the seedling room to the nursery is your next step for getting an early start this spring.

To recap from my last article, a seedling room is ideal for starting a small amount of indoor production, but once a certain number of seedlings are started, it becomes necessary to move into a bigger space.

A greenhouse dedicated to the production of transplants is essential in any market garden operation.

This is not a cheap option by any means, it requires a major investment in infrastructure, for the building as well as for heating and ventilation equipment. 

Since this is our first year as market gardeners and we don’t have a whole lot of extra cash kicking around, Jon and I are opting for a less expensive option for now, a hoophouse. 

Check out my article here for more info on season extension methods.

For the sake of this article, since we are following J.M. Fortier’s market garden model, we will be focusing on using a greenhouse as a nursery.

Planning Your Nursery

When J.M. and team set up their nursery, they used a greenhouse that would also be used for growing crops during the summer season, rather than investing in a smaller permanent greenhouse intended exclusively for producing transplants.

They did this because they only needed a nursery for about 12 weeks out of the year, so having multiple uses for one building made more economical sense.

As well, they could use some of the heat provided for the nursery for other early direct-seeded crops.

They called this their evolving plant nursery. This is a very economical way of utilizing a greenhouse and will definitely help offset the cost.

greenhouse nursery

The Greenhouse Nursery

At the end of winter, J.M. sets up the seedling nursery in part of his large tomato greenhouse, which is sectioned off using polyethylene film.

The partition is clipped to the hoops of the greenhouse, making it easy to move.

This allows them to increase the heated space gradually as transplant production progresses.

Since only part of the greenhouse is used as a nursery, they seed the remainder of the space with early veggies that they plan to harvest for their first market.

In total, the nursery takes half a day to set up.

It is just a matter of laying a geotextile ground cover, to prevent weeds from taking root and installing movable tables.

In the Spring

As spring wears on, and outside temperatures get warmer, some of the inside seedlings are transplanted into the tunnels and under floating row cover in the gardens.

This is a good time to reorganize the nursery, reserving a section for the tomatoes that are ready to continue growing in the ground.

The polyethylene partition is removed, which allows the greenhouse to warm the tomatoes, transplants, and early crops.

Once the danger of frost is over, they move all the transplants outside. This is usually done in late May/early June.

At that time, they also harvest the greenhouse crops (beets and carrots) for the first market, and the rest of the tomato plants are planted over the entire greenhouse space.

Does this sound complicated?

To me it does, but with proper planning, all of this movement results in optimal use of the greenhouse. Since fuel is expensive, it’s worth the effort.

Heating and Ventilation of the Nursery

A nursery needs proper heating and ventilation to produce good transplants.

Do not skimp on the heat.

A mistake that some noobs make is setting the temperature for less than optimal for plant growth (18 degrees Celsius or 64 degrees Fahrenheit at night) in an attempt to save money.

Don’t do this.

Plants kept at a lower temperature will grow more slowly, which delays production.

Since the growing season is so short, you have to make transplants grow as quickly as possible.

When it comes to saving on heating costs, it’s better to improve equipment (insulation, efficient furnace, etc.) rather than adjust the temperature.

It’s also important to make sure that the greenhouse is shut up tightly at the end of the day to keep out the cold wind at night.

As far as the type of heating system goes, oil, propane, or gas, they are roughly the same in terms of heating and equipment cost.

The most important thing is to acquire a furnace that is in excellent condition, powerful, and reliable.

Also, make sure the furnace is the appropriate size.

As far as fuel for your furnace goes, take the time to research the reliability and speed of the services offered by different fuel suppliers.

Some have special rates for farmers, so it’s a good idea to ask.

To ensure even heat distribution, perforated polyethylene pipes may be used. These attach to the furnace and are installed under tables in order to heat the seedling flats first.

The perforations must be calibrated according to the size of pipes and their spacing inside the greenhouse. Most greenhouse suppliers offer this service.

To cool the nursery on sunny days, you can roll with natural ventilation in the form of rolling up sidewalls.

To keep the cold air from touching the transplants too directly, you can install ‘skirts’ along the greenhouse and place seedling tables below the level of the side openings.

In order to regulate humidity, you can roll up the sides of the greenhouse a few minutes very early in the morning to allow any humidity produced through condensation during the night to escape.

You can do this while the furnace is heating the air. This procedure prevents excessive humidity from stagnating in the nursery and works wonders.

Lastly, you will need a thermometer with an alarm that allows you to set maximum and minimum temperatures.

This way, if your furnace breaks down, a power failure occurs, or a fuel shortage, the alarm will alert you that your seedlings are in danger.

This can be fatal to your plants, so have a backup plan in place just in case.

J.M. has a smaller backup furnace in the greenhouse that is maintained and can keep the plants warm enough until the main furnace is fixed.

You can also get a generator in case of power failure. This is a large expense but could save your plants if need be.

As well, the thermometer will alert you if the temperature is too high in the nursery.

Forgetting to roll up the sides when the sun comes out can result in a greenhouse full of dead seedlings in less than two hours.

This can be devastating for the length of your growing season.

The moral of the story, get yourself a thermometer with an alarm.

watering plants

How to Water Seedlings

Water management is essential for producing successful transplants.

Too little water can kill plants, too much water can lead to fungal diseases.

Here are some considerations to keep in mind when watering your seedlings:

  • Watering must be done in a uniform fashion. Every tray of the same cell size should get the same amount of water so that none of them dry up faster than others.
  • Water in accordance with the location of the trays in the greenhouse. Flats dry out faster at the table edges, on the south side of the greenhouse, closer to the heater.
  • Watering must always be done twice. Once to moisten the soil and once to water deep down.
  • Consider the temperature. Sunny weather calls for heavy watering, cloudy weather calls for light watering.

It’s a good idea to have only one person do the watering inside of the nursery. This ensures that the task is never forgotten.

Also make sure the water used is not too cold, as this will slow the growth of the seedlings.

J.M. has a large water tank that they fill up every other day. The heat of the greenhouse warms the water. He also paints it black to help keep the heat in and to prevent algae from forming in the tank.

The reservoir is linked by pipe to a pool pump that is equipped with a pressure tank, This allows them to water as much as they need without having to switch the pump on and off.

Potting Up

Potting up consists of transferring seedlings from small cells into bigger ones.

This gives plants that spend a long time in cells (tomatoes, peppers, cucumbers, etc.) the benefit of extra root space and rich new soil mix to further their development.

This is a delicate process that involves holding each plant by its stem and extracting it from its cell by pinching the cell bottom and gently tugging the plant.

If plants are potted up at the right time, the roots will occupy enough space in the cell so that the clump holds together well.

If you have some weak plants, don’t bother potting up. You only want to grow the strongest plants, the weak ones can be composted along with their soil mix.

Transplanting into the Gardens

After months of nurturing your seedlings, it’s time to transplant them into the garden. YAY!

Step 1: Prepare the plants for the shock they will have when moved outside. One week before the transplanting date put the seedlings on tables just outside the greenhouse and cover them at night with floating row cover. The purpose is to get the plants accustomed to the elements gradually.

Step 2: During the hardening off period (step 1), prepare the beds and make sure they are ready to receive the transplants. Soil is amended, beds are broad forked, and plastic mulch and drip irrigation are installed where necessary.

Step 3: Once the beds are fully prepared, make sure all the transplants bound for the garden have a thorough watering.

Plants take best when there is already a good amount of moisture in the potting mix. The soil in the garden is relatively dry and tends to draw moisture from the transplanted clumps.

Step 4: Follow your crop plan to make sure all of your transplants get planted in the right areas of your garden.

Step 5: When putting transplants into the ground, there are two things to watch out for.

First, it’s important to avoid leaving air pockets between the clump and the hole. The transplants need to be firmly rooted by pressing them lightly into the soil.

Secondly, the clump needs to be buried completely as it will dry more quickly if left poking out of the soil.

By the end of the process, the surface of each clump should be level with the soil surface.

Step 6: For the next few days after transplanting, make sure the ground stays moist. The plant roots can’t go without water at this stage or else the crop will be fragile throughout its growth.

Transplanting is a very important step. You want to take every precaution possible to ensure healthy plant growth so that all your hard work pays off and you have a longer growing season.

Do you have any tips for successful nursery planning or transplanting? Let us know in the comments below.

Stay Local,

Kathy & Jon

your friendly neighbourhood growers


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