Plant Tray Options

We use plant trays or totes to make our plants mobile.  The trick to not using a greenhouse is being able to move plants in and out of the house as the weather conditions change in late winter and early spring.  Plants left inside until the last frost tend to be "leggy" from lack of sunshine.  They will also not be ready to plant since they haven't been hardened off yet.  In addition to mobility, some types of totes also offer shelter from wind or rain, helping with hardening off, and disease prevention.

Listed below are types we have used, their strengths and weaknesses. 

Lined Cardboard Boxes

These work surprisingly well.  We use shipping boxes with the flaps pushed down inside the box.  Line them with a large trash bag and they make a functional plant tote.

Strengths

Cost:  Cheap or free.  Pick used ones up at the grocery store.
Availability Used:  Good.
Availability New:  Excellent
Plant Protection: Good.  Stops wind,  Walls support plants.  Obviously will not handle rain.  If it rains we move them back in the house.
Recycling:  Good.  Can be recycled.
Toxicity:  None
Use in the house
:  With a liner these work fine.

Weaknesses

Durability:  Very low.   Lasted long enough to get us through a spring season.
Reusable
:  No.
Stacking:  No stacking.

Commercial Plastic Crates

Strengths

Availability Used:  Below average.  You might have to drive some distance to pick them up.  Resellers located in cities.
Availability New
:  Good.  Available through commercial material handling suppliers and resellers.
Durability:  Very high.  Amazingly tough.  You may never have to purchase another tote ever.  These are not the kind sold at retail stores in the housewares section.
Reusable: Yes.  There is a whole industry built around the reuse of these items.  
Recycling:  Good. Can be recycled but requires some extra effort.  Standard drop-off sites in our area aren't designed to accept them.  These resell well so unless they are damaged, they don't have to go to the recycler.
Stacking:  Excellent.  Holes allow air circulation and light when stacked.  Saves space.
Toxicity:  None noted:  Made of really hard strong HDPE.  Many are food grade plastic.  No odor.
Use in the house:  Can be lined with a trash bag for use inside.

Weaknesses

Cost Expensive new but used ones are available.  We purchased ours on ebay for $5 a piece.
Plant Protection:  Low.  Line w/ a white trash bag if plants aren't hardened off.   When weather warms, remove liner.  Provides support,  wind protection, and air circulation when they are big.

Non-Commercial Storage Totes

Strengths

Cost:  $7-12.
Availability New:  High
Plant Protection:  Good.  Stops wind, rain, and frost damage when plants are small.  Provides support when they are big.
Recycling:  Good.  Can be recycled but requires some extra effort.  Standard drop-off sites in our area aren't designed to accept them.
Use in the house:  Good.  You can water the plants and your house stays dry.

Weaknesses

Availability Used:  Very low.
Durability:  Low. No UV resistance.  Not very thick.
Reusable:  Not very reusable in this application.  After a couple seasons of sun exposure, they crack.  Especially the really long ones.  Put them away as soon as the seedlings are planted.

Toxicity:  We're not sure but we think new smelling containers are releasing a chemical that may affect plants.  Recommend washing new containers with soap and water prior to use.  Don't use the lids unless you have to.  Older totes don't seem to have the same effect.
Stacking:  Can be stacked but stops air circulation.  Not recommended.