Lambeth Horticultural Society

“STARTING FROM SEED”

Written by our own resident expert Peter Calvert

It is best to use a plant tray with cell pack inserts and clear plastic top.   Although there are many kinds of soil mix for starting seeds, the best and easiest to work with is “Pro Mix BX”.  In using Pro Mix, use a starting fertilizer with a reading approx 10(N) 52(P)10(K) at 1/4 normal strength and dilute in water.  In a container, mix Pro Mix with enough fertilized water to make it moist but not wet.   Fill the cell pack inserts with the damp Pro Mix and level evenly: do tamp this lightly especially around the perimeter.  Sow the seed according to the instructions on the seed package.  Sow thinly (a ( 3×4 ½”) insert should only have about 50 seeds).   It is most important to take time to see that you space seeds evenly.  Some small seeds like petunias or begonias are difficult to sow but many seed companies sell pelletized seed and these are well worth the extra price.

Put the seeded insert in 1/4″ fertilized water to let the water percolate up.  As soon as the water starts to show on the top remove and place in the tray with the clear plastic cover and place in light.  Most seeds germinate best at temperature of 80F.  A small thermometer in the tray will assist you in this. The heat can be attained with a heating pad or any other method that will ensure the proper temperature. The seeds need 15 hours of light.  If you use fluorescent lights, the tubes should 7-9″ above the seed insert.  You should not need to add water until after you remove the germinating seeds.  When the seeds germinate and a third leaf is showing, remove the clear plastic cover and grow the plants at a cooler temp. 60-65F.   A fan will also help to circulate the air which will help eliminate disease.  When the seedlings are about 3-4 weeks old, it is time to transplant to individual containers or cell pack inserts.   Stokes Seeds has the best instructions on the seed packages.

The following chart will give you a time guide to help:

Young plants must receive lots of light and cool temperatures to prevent them from getting too tall and falling over.   When the weather gets warm in April , place outside on warm days and bring in at night.  Water only when soil appears to be drying.  Fertilize with a water soluble fertilizer, every two weeks, with equal parts N.K.P.   All plants must be hardened outside before planting in the garden.   If you are using a cold frame, plant about 1 week earlier than above.