More or less Practically any kind of seedling can be transplanted.
Plants almost always grow best and fastest when seeded where they are to stay. And seeding directly is easier on the gardener, too. If you can raise a plant by seeding it directly into the soil, do so -- for that is nature's way.
Yet, there are good reasons for wanting to transplant seedlings. Here are the main ones:
1. To get an earlier start. This is the reason warmth-loving plants such as tomatoes, peppers, and eggplants are seeded indoors about two months before the weather is mild enough for them to be in the garden. Then when you move them to the garden as plants, it is as though your season started about two months sooner than it really did.
2. To protect plants while they are young and most vulnerable. Pests such as slugs and cutworms can wipe out an entire bed of tiny just-sprouted plants. But vigorous seedlings when moved to the garden can have a much better survival rate. Transplants aren't pest-proof but they are less likely to succumb to pests than the brand-new babies.
3. To save garden space. Suppose you have bush beans bearing in the only space available for late lettuce. By starting the lettuce in containers, you give the beans time to complete their bearing cycle before the ground is given over to lettuce. If you seeded the lettuce directly, in time to get a crop, you'd have to phase out the beans before they had finished their job.
How to Transplant
First lets take up containers and soil mixtures in which to grow seedlings for transplanting.
Containers: We use mainly two kinds, plastic containers about 3 by 5 inches, divided into six cells; and peat pots. We fill such containers with a commercial potting soil mixture, sometimes mixing it, about three parts to one, with milled sphagnum peat moss or with vermiculite for more water retention. But we have used many other sorts of containers, including wooden flats and plastic ones, egg cartons (punch a hole with a nail in the bottom of each compartment for drainage), peat blocks, and 3-inch squares of sod turned upside down -- an old and workable way to grow large-seeded plants such as grow large-seeded plants such as marrows.I try to put only one seed in each place where a plant is to grow, covering it lightly with vermiculite. We then water the container well, until water runs out the bottom. Then I enclose the container in a clear plastic bag, close the open end of the bab securely, and put the bag in a light but not sunny place. In cool weather we put it on a heating cable sold for this purpose (a 12-foot one, from garden suppliers, heats soil in containers to about 18-23 degree celcius.
Just as soon as seeds start sprouting, we remove the plastic bag. We then grow the seedlings, indoors if the weather is too cold for them, otherwise outdoors in a coldframe, until I need them in the garden and they are doing well.
The usual recommendation is to wait for transplanting until seedlings have their second set of true leaves.
Young transplants need a little temporary protection from sunshine,and colder nights so for a few days I make a temporary cloche from 1' plastic tubing and cover with the green wind break material.