Gardening Q & A Lessons To Grow! Natural Play Pure Science

Starting Seeds Indoors with Kids…SQUISH!

Teamwork:  Some Plants Need A Boost and Some Kids Like To Squish Soil

 Some of the plants we love need a longer season to produce the summer vegetables we love to eat.  Starting seeds indoors is one way to give your garden a head start. Tomatoes, peppers, broccoli, basil, cabbage, kale are some of the veggies that need the extra boost.  Native plants, grasses, and annual flowers may be started indoors too.  Seeds will fit into three categories and the package will say if they should be starter early indoors, outdoors as soon as the soil can be worked, or outdoors after the last frost date.  Over the years I’ve tried many ways and products for seed starting, and this is the method that has given me the strongest plants in a cheap, user-friendly way.  The biggest lesson I’ve learned from seed starting indoors?  It’s as much an art as is science.

OVERVIEW.  The three easy steps are:  1) gather materials, set up the light for seedlings, and plan your garden, 2) seeds are started in sterile starter mix then 3) about 4 weeks later they are transplanted into soil in containers.  Most tomatoes and peppers should be started 6 weeks before the last frost date.  Some gardeners start their seeds the first or second week in April (in Minnesota), other decide based on moon phases, other their gut feeling.   Know that for every tray of seeds in starter mix you will need 2-3 trays of containers with potting soil for round 2.

SET UP A NURSERY FOR BABY PLANTS.  What will you need?  First of all, you’ll want some kids to help you out and you’ll want to plan about an hour for the activity.  Basic supplies are:  rectangular black planting trays with lids, seed starter mix, fluorescent light source that can be placed 3 inches above soil height, duct tape, permanent marker, and plug-in timer for the light.  If you are reusing trays, be sure to clean them with a bleach solution.  This kills the germs responsible for the disease called damping-off in which the seedlings grow nicely for a short time then collapse when stems are weakened.  Starter mix is made up of peat moss and vermiculite- its purpose is create a clean place that holds a lot of moisture while the seeds are taking off.

GET MESSY.  It will be messy but not terribly.  Note that soil contains living things like bacteria, fungus, and critters that plants need to grow.  The starter mix does not have those things yet because the seed has its first foods packed inside.  I place a sheet on the floor with a large storage tote in the middle to make clean up easier.  An ice cream bucket filled with water can act as a “hand-dunker” to rinse off the loose stuff from messy hands.  Place some starter mix in the bin and add water.  Kids usually do a great job of squishing the starter mix between their fingers to work the water into the mix.  Add water and mix until you have a consistency that is clumpy and wet but NOT soggy and drippy.  Make enough to fill the tray(s) 1.5-2 inches deep.  Before filling the trays, place a strip of duct tape along the long edge on the outside of the tray for labeling purposes.

TRAY IT UP.  The seeds need a warm and moist place to begin to grow, germination.  Once the trays are filled with the wet starter mix (1.5-2 in depth) then have the kids smooth it out but NOT pack it down.  Just like insulation in a winter coat, the pockets of air in the loose, wet starter mix will trap heat.

ROWS.  Preschoolers and toddlers will love putting their math minds to work when they create 8-10 short rows per tray.  Each row should be about 2 inches from the next and about ½ in deep- chopsticks or popsicle sticks work well.

MATH & PLAN.  Now you have set up a great opportunity to apply math!    If we have 5 seeds in each of 10 rows, how many plants might we get?  Will we have room in our garden if we plant 10 tomatoes seeds in 8 rows?  How many trays will we need for our indoor seed starts in step 2 if we plant 100 seeds here?  Will every seed we plant sprout- Why or why not?  What percentage do you think will sprout?  How could we create a chart to show what we planted and when they sprout?  Be sure to label the variety and number of seeds on duct tape label on the long edge of the tray in front of each row.


PLANT.  Each seed package will say the depth and spacing of the seeds.  If you keep all of the rows uncovered until the very end, then kids can see the different types of seeds all at once and reduce the chance of doubling up on a row.  Gently cover the seeds with starter mix.  Do not pack it down.  Place the clear plastic cover on top of your seed tray.

WATCH.  A light source, set on a timer for 16 hours of light, is essential for strong plants.  The tray should be set in a place where the bulb is nearly touching the top of the tray cover.  Keep the cover on until the first true leaves are well established (the cotyledons look like leaves but they are actually part of the seed).  The seedlings will grow toward the light- if that’s a sunny window your plants will grow sideways and spindly.  Preferably, a fluorescent light hung from a shelf or stand can be raised or lowered with chains.  Small fluorescent lights, designed to be mounted under cabinetry, can be purchased at hardware stores for a reasonable price.  If you find a light source that has hardwiring only, many stores will wire a cord with plug-in, especially if you mention the project is for a classroom.  If you already have a fluorescent light under the cabinetry, then place the tray on stacks of books until the bulb is right above, almost touching, the clear plastic tray lid.  As the plants grow you will be able to remove books to adjust growth space for the plants.  Do not add water to the starter mix.  Water that was squished into the mix provides enough moisture for the seeds.  Condensation collecting on the tops and sides of the lids is a good sign.

WAIT.  Eventually the seedlings will grow tall enough to reach the tray lid.  Do not remove the lid all at once.  Instead give the plants a chance to adjust slowly by creating a ventilation crack with a pencil, ruler, or stick in-between the lid and tray on one end then a few days later increase it to both ends.

TRANSPLANT.  Now that at least 3-4 weeks have passed, your seedlings are ready to be transplanted into potting soil.  A sure sign is when the first true leaves (looks like 2nd set of leaves) appear.  This timing will vary for the plant type (kale, tomatoes, peppers, etc) you are growing.  Yogurt cups with holes in the bottom, egg cartons which can be watered from the bottom, or plastic sectioned plant pots that can be purchased are all good options for containers.  Gently dig up the seedling roots (no stem pinching) then lift it into a container filled half full with potting soil and add a little water.  Gently place potting soil around the seedling roots and some of the stem.  Tomatoes like to be planted deeply or even sideways up to the first leaves since those little fuzzy hairs on tomato plants become new roots.  Line up the new containers in the rectangular black trays and water them from the bottom.   Resist the urge to water from the top.

LIGHTS ON.  Place your trays with little seedlings under the lamps again.  This time without the lid.  The lamp bulbs should be just about the plant tops.  Check the plants everyday, and water from the bottom as needed.   Some specialty garden stores sell root stimulator (nitrogen, phosphate, potash) that can be mixed with the water you add to the bottom of the trays.  I do not recommend using products that contain plant hormone stimulators.

OUTSIDE.  Those tiny plants need to be eased out the door, just like an elementary school kid slowly eating breakfast on a Monday morning.  Now is the time to move them to a sunny window and turn trays daily as they will grow towards the light.  Once outdoor temps are warm enough begin placing the trays outside for the “hardening off” process.  “Hardening off” the plants means slowly helping the plants adjust to natural sunlight and cooler temperatures.  After 5-10 days with days outside and night times inside and warm enough soil temperatures then you can put them into the garden or pots outdoors.  In the Minneapolis Metro area, that is typically the end of May. Trays can be rinsed and stored away until next spring.

Play. Learn. Love.

April 2014