Gardeners can be quite resourceful when it comes to finding containers to use for starting their seeds.
If you have purchased plants from a greenhouse in the past, you are familiar with a black thermoformed plastic tray called the greenhouse “flat”. These typically measure about 11″x21″ by 2-1/2″ deep .
The flat in turn has a black plastic liner or “insert” placed into it. The inserts are commonly divided into sections ranging from 24 to 72 “cells”.
This system of greenhouse flats works wonderfully for use in the greenhouse because all of the starting and growing containers are standardized and easy to handle.
Flats are also available for use at home, either at well stocked garden centers, on-line, or through gardening catalogs. They work just as well at home as in the greenhouse if all of your seeds require the same growing conditions.
Back in the old days, greenhouse people used to make their flats out of untreated wood. A typical size was 16″x24″x3″. This is still a good option for some gardeners.
If you only have a few seeds of each variety and they have widely different sowing and growing conditions, then a flat might not work for you. Several smaller containers must be used to accommodate the different seed requirements.
This is where you can use your imagination to find containers in which to start your seeds. Most commonly you see folks using recycled milk cartons or jugs cut to size. With today’s over-packaging of food products, we have a huge selection from which to choose. Previous generations didn’t have this wide variety of choices.
Look around in the trash and you can find yogurt cups, egg cartons, snack containers, frozen food packaging, fast food packaging and more; all of which has potential to be recycled for use in starting seeds.
Whatever you decide to use for your container, it absolutely must have drainage holes. Cut or punch out several holes in the bottom to allow excess water to drain away.
You can use newspaper to make your own paper pots. Cut the newspaper into 3-1/2″ wide strips and wrap them around a glass jar a couple of times. Tape the paper where it overlaps and fold the bottom of the paper to make the pot bottom.
Since I’m a “saver” type of guy, I like to save my plastic flats, liners and pots from season to season. Many people say they don’t like plastic pots because they don’t degrade in the land fill. I say that’s their best attribute, the plastic holds up well from year to year and can be re-used. Just don’t be in such a hurry to throw them away every year.
Some of last year's greenhouse flats waiting to be washed, disinfected and re-used.
When re-using pots, make sure they are washed to get off all of last year’s soil. Then sterilize then by using a 10% bleach solution:1 part bleach to 9 parts water. If you don’t thoroughly clean them, you run the risk of transferring disease to your seedlings.
Common garden soil cannot be used to start seeds indoors no matter how good it grows crops outside. Soil dug from the garden is just too dense and will form a hard mass in the container making it extremely difficult for the plants to grow.
Seedlings need a soil that is able to hold water, yet can still drain away excess moisture. The roots also need a certain amount of air in order to grow properly. Some gardeners try to blend their own starting mixes but this is not recommended for beginners.
The soil that is used to fill your containers must be sterilized for the same reason you sterilize the pots: disease prevention.
To get all of the characteristics of a good seed starting soil, it is easiest to purchase a bag of packaged seed starting mix. These have already been sterilized by the manufacturer. Be sure the mix is labeled as a seed starting blend and not a potting mix. Potting mix is usually to coarse for starting all but the largest seeds.
In the next blog we’ll discuss filling your containers and sowing your seeds.