Preparing for Spring Transplants

Seed flats in the greenhouse in early spring. See the large lettuces growing in the beds, between flats of seedlings balanced on the bed walls.
Photo Kathryn Simmons

Preparing for Spring Transplants

We have winter to enjoy/experience/endure before we start spring seedlings, but there are some steps you can take to make spring start-up easier and more successful. Of course, there is the usual list of tidying your workspace, preparing to order seeds and repairing tools.

Replacement tool handles

House Handle Company   Telephone: (800) 260-6455 has a wide selection of good quality wood handles online. They specialize in hickory, white oak and ash. Be careful making your selection, and get the handle that’s just right for the tool you are repairing. You can see a lot of their handles in our photos. During the winter we usually have a “Santa’s workshop” day when we repair tools.

There are YouTube videos showing how to make sturdy repairs. Just be sure to shape the handle for a good fit before drilling any holes for rivets. And learn how to make rivets from large nails if none are supplied with your replacement handle. Sharp edges on poking-out badly finished rivets, or nuts and bolts can cause injuries. Sweat we might need. Blood and tears we can do without.

Screening a large pile of compost for the greenhouse beds. Photo Wren Vile

Seed Compost

Today I’m thinking about seed and potting compost.

We use 100% home-made compost for sowing seeds, and for potting-up transplants. We don’t mix in any other ingredients. Our seed compost is our regular good-quality compost, screened to remove large particles, and matured over the winter into a very mellow combination of nutrients and micro-organisms. We make great compost and it grows big strong plants.

We screen a big pile of compost in September, and fill the cinder-block beds in our solar-heated greenhouse. See this post: Screening compost to make our own seed compost for spring. If you are making your own screens, you can use hardware cloth (rat-wire), or do as reader Jim Poole suggested and try stucco lathing instead. “It is quite a bit sturdier. (But watch out for the cut ends when installing it- it can give you a nasty gash.)”

We need a lot of compost, but the idea works fine on a smaller scale too. Find an indoor place near where you will use the compost in the spring, and some tubs to put the screened compost into. If you want the full tub to be on a bench in spring, put the empty one on the bench and screen into it! If you want to grow lettuces in the compost, put the tubs near a window.

Just storing the compost inside over the winter will mean you are not dealing with frozen stuff when you want to sow. But better yet, see Starting Seedlings and Preparing for spring, sowing seeds, for more about how we grow lettuces in the stored compost over the winter in our greenhouse, then use that compost in spring for seedlings.

Greenhouse beds filled with screened compost.
Photo Wren Vile
Lettuce growing in screened home-made compost in our greenhouse in November.
Photo Wren Vile

We transplant lettuce at 10″ spacing into the beds in mid-September or early October. By harvesting only the outer leaves, we keep those lettuces alive and growing all winter to give us salad from November to February. Because we water the lettuces, the compost organisms stay alive and active. If you don’t grow a crop overwinter, water the compost from time to time to keep it slightly damp.

This system provides us with a large quantity of mellow screened compost for seed flats, indoors and not frozen. The micro-organisms have had plenty of time to colonize the compost, so it is full of life. In spring, as we need space in the greenhouse, we pull the lettuce. We can then scoop out the compost to fill the flats for seedlings.

Aphids

The only issue we sometimes have is aphids in early spring. This winter we are experimenting with some plants we hope will flower in early spring and attract beneficial insects who also eat aphids. I’ll report on this project when we see the results.

Here’s what we currently do to deal with early spring greenhouse aphids:

  1. jet the plants with water to project the aphids into outer space (OK I’m exaggerating),
  2. gather up lady bugs, or
  3. if numbers of aphids are really high, we use a soap spray.

We start our first seedlings in mid-January, although we only sow a few things the first week (cabbage and lettuce for outdoors and tomatoes for our hoophouse), and harvesting just one or two lettuces would provide enough compost for those few flats.

Lettuce transplants in soil blocks. Photo Pam Dawling

Soil blocks

We used to make soil blocks for our more delicate transplants (melons, early cucumbers and squash) because there is no transplant shock when you plant them out. We even used them for lettuces at one time. We developed a very simple recipe, which we seem to have lost, but it was something like 1.5 parts by volume of our home-made compost, 1 part of soaked coconut coir and as much water as needed to make a wet slumpy, but not soupy, mix.

I use coir rather than peat moss, because I believe the extraction rate of peat moss is not sustainable, and as a carbon sink, it’s better to leave it in the ground. Coir is a tropical food by-product. I’m sure it’s better returned to the soil where the coconuts are grown.

The mix is compressed into a special block-maker, which is then scraped across an edge of the container of mix, to create a flat base, and then the block is ejected using the spring-loaded handle into a tray or open flat. We line our flats with a sheet of plastic to reduce drying out. It’s important to dunk the block maker in water between fillings to wash off the old remnants and enable the new blocks to slip out smoothly.

The blocks are surprisingly stable – they can be picked up and moved, like brownies. Or you can move several at once on a kitchen spatula. As the plants grow, the roots get air-pruned. Even if you pack the blocks shoulder to shoulder in the tray, the roots from one block do not grow into the others. There is no root damage at all when the complete block is transplanted. Do make sure you press the surrounding soil down and inwards to make good contact with the block.

Okra seedlings in a Winstrip tray in the greenhouse. Note the vented cell sides.
Photo Kathryn Simmons

Winstrip trays

More recently we have come to love Winstrip trays, very durable plug flats with cubic cells that are vented down the sides, so the plants get air-pruned. The bottoms of the cells have finger-sized holes so you can easily pop a full-grown transplant out of the tray. The Winstrip 50 cell tray has cells almost the size of soil blocks. These flats have all the advantages of soil blocks except price. They are expensive. We got ours used. Winstrips have two additional advantages: they are much quicker to use than soil blocks, and they work with all-compost. We don’t add any coir. One less input to buy. I haven’t calculated how many plugs-worth of coir pay for one Winstrip tray. . .

See this post on using Winstrip trays and transplanting plugs from them

For more about soil blocks, and Winstrip and other plug flats, see my book Sustainable Market Farming

2 thoughts on “Preparing for Spring Transplants”

  1. Thank you for the recommendation to water the compost brought in the greenhouse for spring seeding. I also bring tubs of compost in the greenhouse in the fall – but had not thought of planting them and/or watering. That makes sense, and I will do both.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.