As new market farmers with limited gardening experience, we plan on growing and using our own transplants for most of our veggies.

Growing your own transplants is a good way to start your season just that much earlier, allowing you to be out at the farmer’s market selling your veggies on the first weekend it opens!

That’s our plan anyway, fingers crossed we pull it off!

As well, if you grow your own, you can get the mix of varieties of veggies that you want and keep them in great condition until you plant them out.

You can also provide yourself with extra plants ‘just in case’ at little extra cost, and reduce your stress.

Another bonus is that if you are growing green manure cover crops over your garden beds, transplants allow extra growing time.

Transplants allow for a little extra wiggle room if you can’t get your seeds sown on the correct date for circumstances beyond your control, like the weather for example.

For this article, we are turning to the author of Sustainable Market Farming by Pam Dawling for her expert advice on transplants.

Basic Equipment Needed for Transplants

To start your own transplants, you will need:

• A warm well-lit space
• A collection of flats and/or plug trays
• Some potting compost
• An area for hardening off the plants before planting out
• Enough time in your days
• A plan

Many seeds benefit from some heat during germination and are then moved into slightly less warm conditions to continue growing.

This means it is possible to germinate seeds in a relatively small space.

Electric heat mats can be used, with the flats sitting on top.

Many people construct some kind of insulated cabinet to start their plants, with fluorescent lights suspended above the flats.

On Pam’s farm, they use two broken refrigerators as their insulated cabinets, with extra shelves added. A single incandescent lightbulb in each supplies both the light and the heat. They change the wattage of the bulb depending on what temperature they’re aiming for.

Hardening off Transplants

Pam uses two old-style cold frames for hardening off their plants. Hardening off helps the plants adjust to cooler, brighter, breezier conditions.

The cold frames are rectangular of dry-stacked cinder blocks with lids of wood-framed fiberglass. The flats are set directly on the ground in the frames.

This is a good option for young market farmers, but for anyone over 35 (like us), having heavy flats of plants at ground level is less than ideal!

Shade houses and single-layer poly hoop structures with ventable sidewalls and benches for the flats are nicer options.

Pests may be less likely to be trouble when flats are up on benches.

Depending on nighttime temperatures, the plants are covered with row covers for 32-38 degrees Fahrenheit (0-3 degrees Celsius), add the lids for 15-32 degrees Fahrenheit (-9 – 0 degrees Celsius), and roll quilts on top if it might go below 15 degrees Fahrenheit (-9 degrees Celsius).

Once hot weather starts, shade cloths are used to cover the cold frames or row cover for pest control, and the lids get stored until late fall.

It’s important to know that seedlings need warmth, ventilation, and watering, and you will probably need to check on them at least twice a day. So, make sure you have the time to devote to your seedlings before you begin.

Having a plan in place saves a lot of potential mistakes and stress later. 

Seedlings Schedule

Some of the info you need before getting too far into the growing season is how many of which transplants you need and when you need them.

When you have a rough idea of how much of each crop you want, you have the info needed to start transplant planning.

My husband, Jon, has spent many an hour working on our crop plan so we knew approximately how much seed we need to order of any given crop.

Here is our crop plan (still a work in progress):

Our crop plan is a spreadsheet that lists in order by date all the transplants we need to produce and when we need to sow them to have them ready to go into the ground at the right time.

It is in date order and lists the crops, varieties, and how many rows of what length we intend to plant. This information comes from the work that has already been done at the Crop Review, Seed Order, and Garden Layout stages.

To create this, Jon took all the crops we plan to transplant, looked at the transplanting date we aimed for, and decided on the sowing date, taking into consideration our last frost date in the spring.

After setting up all the other columns, he sorted the spreadsheet by sowing date.

A good rule of thumb for planning your seedling schedule is to include the dates of in-row spacing of each crop (plants per 100ft.) and formulas that calculate how many transplants will be needed, allowing 20% extra of most things.

For example, 1,080-row feet of spinach at 200 plants per hundred feet would be 2,160 plants. 2,592 is 20% more than 2,160, which allows you to choose the best ones when planting and have a margin of error to account for casualties.

Open Flats

For brassicas, lettuce, and paste tomatoes, Pam uses open flats (simple wooden boxes). 

The transplant flat size is 12” x 24” x 4” deep. It holds 40 plants ‘spotted’ or pricked out in a hexagonal pattern, using a dibble board.

The column labeled ‘Flats plan’ on her seedling schedule tells her how many transplant flats she will need.

Seedling Flats

These are Styrofoam cell or plug flats which were originally made for the tobacco industry. They are used for onions and spinach especially because the seedlings can be grown to full transplant size in them, they are light and easy to use, and the plugs can be pulled out or eased out with a butter knife if need be.

Cell flats/Plug trays

On Pam’s farm, they transplant by hand and hate to throw plastic away, or spend money when they don’t need to, so they use a range of different plastic containers.

For crops that they grow only a small number of plants of each variety, they use a 6 or 9 pack, or a tray divided into smaller units.

They use deep 9 packs for tomatoes, which are later potted up into a 3.5” pot; round 38-cell cheers; Winstrip vented square cells and some soil blocks.

Soil Blocks

These are handy for early cucurbits (cucumbers, squash, and melons) as these seedlings are harder to transplant and the soil blocks minimize the transplant shock.

Soil blocks are made from a mixture of compost and coir (coconut fubar) or peat moss, and sometimes other plant nutrients.

Pam uses one part coir to 1 ¼ part of good quality screened (sieved) compost.

Plenty of water is added to make the mixture sloppy, and then it is compressed into a special soil block maker and ejected into a tray of some kind.

Seeds are sown in the top and covered with soil.

The blocks hold moisture well and are quite stable.

When the roots of the plants reach the edges of the blocks, they get air-pruned so there is no root damage at all when the complete block is planted out.

This is the method we are using to start our transplants this year, so stay tuned for our thought on soil blocks in the future!

Using a Hoophouse for Transplants in Spring and Fall

Sowing in a hoophouse can be done for hardier early spring seedlings. The plants grow sturdily, need little attention, and transplant outdoors nicely when the time comes because they have already been hardened off by the nighttime temperature in the hoophouse.

In the fall, onions are sown in the hoophouse for outdoor transplanting as early in March as is possible.

Age of Transplants

The first crops sown are not necessarily the first ones planted out. It’s important to keep track of your planting dates for each crop so you stay on top of your seedling schedule. 

There are early season timings and as the days warm up and get longer, the seedlings grow more quickly.

Managing Your Transplants

If space is limited, you might need to schedule more tightly. 

For example, if your germinating area can only hold a maximum of 24 flats at a time,  you might have to wait until some sowings have germinated and can be moved on before you sow the next crop.

You will have to play around with your hoophouse or greenhouse storage of plants in the spring to find a solution that works for you and your situation.

It’s a good problem to have if you are stepping over lots of seedlings in your hoophouse!

Outdoor Planting Schedule

This should be the next spreadsheet in your repertoire of crazy amounts of spreadsheet organization! It might even be part of your crop plan or seedling schedule spreadsheet.

As long as you know which spreadsheet your information is found, you can call them whatever you want!

Once your transplants have reached their outdoor planting date, it’s time to plant them into the ground outside!

This, of course, requires planning as well. Planning out all of these steps ahead of time, like in the offseason if you have one, will save you a ton of time and stress come growing season.

Do you have any tips for successful transplants that you might want to share? Please leave any advice in the comments below.

Stay Local,

Kathy & Jon

your friendly neighbourhood growers