Potting Up Seedlings

Part 1: Greenhouse Seed Starts
Part 2: Potting Up Seedlings
Part 3: Transplanting Seedlings

Starting seeds in the greenhouse is only part of the process.  Those little cells won't allow a seedling to grow.  It's too cramped in there.  Once they have sprouted and grown to an inch or two in height, they will need to be moved to a larger container.  If there is not enough light, it makes the plants reach for light.  This makes them leggy.  The long, thin stems make the plants susceptible to damping off.  Your plants will benefit from being moved to a larger pot at a more suitable depth.  This step is known as "Potting Up".

I use drink cups.  They are cheap, readily available, are made of the same material and are larger than plastic plant pots which cost more.  Most importantly, these can be used repeatedly.  These are available in supermarkets ranging in size from 12-20 ounces.  A package of 100 will run you about 6 bucks, 12¢ each.   If you order $50 or more from Walmart, 8 packages, they'll deliver for FREE and you get a couple of boxes to put to use.


Walmart brand 18 oz drink cups $6.34 for 100



I'll put them to use with my morning coffee first.  Save me the dishes.  Give them a rinse and stack them up for when I need them.  These cups will hold up for many uses.  Before you can use them for plants, you'll need to cut some holes in the bottom for water to drain.  A handy utility knife will do the job nicely.  If you don't have one, try a paring knife.



Cut 3-4 holes from the bottom corner.  A half inch long, 1/8" wide will suffice.  The objective is to allow water to drain without the soil spilling out.  Note the size of the chads and yardstick for scale.



Fill about 3/4 full with your potting mix to allow space for the seedling.  Some seeds grow too quickly for those little cells.  Squash and corn, for example, would outgrow those cells in just a couple days.  Starting in the cups makes good sense.  Leave some room for adding more soil to those plants started from seed.  Here I have some Broccoli: Waltham 29 from Sustainable Seed Company.   As you can see, these seedlings are just about to fall over.  If these plants stay in the cells any longer they will become leggy and have a hard time developing a good crop.



I remove the seedlings from the cell with an old fork.  The size of the end is a good fit for the bottom of the cell.  Slide the fork along the side of the cell, being careful not to puncture it.  Give it a little wiggle, the seedling will lift out.



Here you can see the length of the root.  When you see the roots just starting to come out the bottom of the drain holes in the cell, it's ready to pot up.



Place the seedling in the center of the cup.  If the soil in the cup is moist, you can make a hollow to receive the seedling.  If the soil is dry, use the fork to dig a hollow in much the same way you would make a hollow in mashed potatoes with the gravy ladle.  The objective is for the cotyledons to be just above the rim of the cup.



Add soil around the seedlings, keeping them centered.  The objective is to keep the new leaves above the soil.



Add plenty of water and place on a tray.  Here I use a tray from a package of pork chops.  Those 1020 trays seen in Greenhouse Seed Starts work well and hold 15 cups.



These plants have all the room they need to grow to several inches high.  Their roots have room to grow several inches deep.  They can stay in these cups for a few weeks.  This gives you time to start them well before the last frost, grow them to a fine size, and have them ready for transplant after the first frost date. 

-Different colors can make it easy for you to organize.  Pink for herbs, green for root crops, red for flowers, blue for stem crops. yellow for fruiting plants, green for...greens.

-Most disposable cups will work.  I've even used plastic bottles.  Bottles with ribs make it difficult to slide the plant out when transplanting.

-If you have limited space, greenhouse plants will give you something ready to go when something comes out of the garden beds.

-Because the plants are several inches high when transplanted, they can be deeply mulched immediately after transplanting.  This retards weeds and keeps the moisture in the soil.

-Plastics photodegrade.  These cups are no exception.  They won't last forever.  Over time they will become brittle when left in the sun.  Store them in a covered box in a corner or under a counter when not in use to extend their useful lifespan.

When the plants are of suitable size, people will buy them.  I've sold hundreds of plants in these cups for a buck each.  12-pack beer abd soda boxes can be had for free (check your local liquor and convenience stores.  They'll fit a dozen plants.  I've found that if a box will fit a dozen plants, people will buy plants by the dozen.  Labelling the cups can be done with cut up mini blinds.  If you put one marker with a group of plants, they take the one with the marker.  Of course, without the marker you'll have no idea what the rest of the plants in that group are.  A Sharpie will write on the cups beautifully and not wash off.


Part 1: Greenhouse Seed Starts
Part 2: Potting Up Seedlings
Part 3: Transplanting Seedlings