Archives > February 2017

Seeding:  Seed Depths and Seed Coverage

When it comes to the actual nitty gritty of getting the seeds in – the depth at which they are seeded and whether they are covered or not can make it or break it for success with germination. Here are a few notes from our experience:


THING #1 before you even start this procedure:


Make SURE your seeding trays have water drainage holes!!


  • The rule of thumb for seeding is: sow the seed twice the depth as the seed width.
  • Sow seeds in rows so the seedlings are organized once they germinate.
  • Avoid seeding thickly, sow moderately so the seedlings have adequate space to grow
  • Rule of thumb for covering is: any seed the size of a Salvia or a Pansy seed and larger should be lightly covered with vermiculite (our choice) or the same fine seeding soil to keep them moist. We actually keep a salvia seed taped on our seeder as a visual guideline for covering seed.
  • A Salvia seed and a Pansy seed are pictured in the accompanying photo – Pansies are the smaller seed & require less covering, so cover lightly; and as seeds get larger, they need more covering material.
  • Keep everything moderately moist – too wet or too dry both affect germination. If they are too wet, they will rot – that’s why it is so important that your seed tray has drainage holes and if they are too dry, they dry out and cannot germinate.

Scarlet Lily Beetles – Quick Guide

scarlet lily beetle infographic

Seeding: Soil & Fertilizer

Seeds have a few unique requirements from mature plants. They need a special soil blend and have different fertilizer requirements.



  • Use a soil specific for seeding.  Seeds require a fine soil and it is usually made mostly of a peat moss base.  It has a fine texture so that the microscopic root hairs have no
  • trouble growing and reaching out into the soil as it grows – a coarse soil is difficult for the root hairs to expand into and will consequently slow their development.
  • Seeds don’t need a lot of soil to germinate in – less is more, like 1-1½ inches max– it keeps the seeds from getting too wet – keep the soil moderately moist.
  • A plastic cover could be loosely placed over the seed in a slightly angled manner – you never want that seed flat sealed – so that air can circulate BUT check that it doesn’t get too hot – most annuals germinate in 18C–21C (65-72F)


  • Do not use soil that has a fertilizer infusion. Fertilizer will burn the microscopic root hairs.
  • Use only clear water at the germination stage.  Fertilizer should not be introduced until the first true leaf has emerged – remember that the first 2 leaves are cotyledons, they are not true leaves.  Wait until the third leaf, which is the true leaf, emerges.
  • When the true leaves emerge, use ¼ strength 20-20-20 – avoid root boosting fertilizers that look like 10-52-10, with a high middle number, it’s just too strong and burns the root hairs.
  • In general, seedlings do not need much fertilizer, and if the leaves are a healthy green, probably apply a fertilizer to seedlings every 2 weeks or less often.



Seeding: Getting the Timing Right

Probably the greatest temptation at this time of year as winter wanes on and we begin to itch for spring, is to get some plants started at home.  Before you do, take some time to do  a little research into what the optimum timing is for your plants.  These are the things that you should consider when looking for the best date:


  1. When is the best time for planting outdoors? In our central Edmonton climate, we at Wallish Greenhouses target our plants to be ready for the middle of May.  The risk of frost decreases for each day we get further into May.  Check out this link to Growing Indoors at Home – Pitfalls to Avoid.


  1. Determine the number of weeks needed to maturity (which means the same as days to blossom) – the web has a lot of information on this – ie. Google ‘pansy days to maturity’. For most annuals, it’s around 6 weeks. But, you may not want them to be blooming when you plant them outside – that’s a personal choice – so decide how many weeks you would like to use.


  1. Remember that plants tend to grow faster and stretch in homes when they are grown on a window ledge – the environment is warmer, less ventilated, and generally the lighting is lower. For that reason, you may want to decrease the number of weeks before planting.


  1. Back track on the calendar and that should give you a pretty close estimate. Here are some scenarios:
  • Example 1: Pansies are quite cold hardy, tolerating up to about -4 or -5C, so they can be put outdoors by the second week of May (as long as there is no snow).  Pansies take a bit longer to mature and need about 6-8 weeks.  Backing that out, seed pansies no sooner than the middle of March.
  • Example 2: If Marigolds need 4-6 weeks before planting outdoors and if you would like to plant them out on May 21 (Marigolds are pretty hardy and can take a little cold), your target date for seeding would be around April 9.
  • Example 3: Cold sensitive cucumbers and squash should be left to plant outdoors later,  like the first week of June because of the risk of frost. If you plant them outside earlier than that, you need to be ready to cover them to protect them from the cold.  They are rapid growers, so seeding them 3 weeks in advance would probably work out best unless you are ok with dealing with huge transplants.  For those, a seed date of the 2nd week of May would work.


Stay patient, earlier doesn’t always result in a better plant.

Seed Storage Tips  


How seeds are treated and stored has an impact on their viability and how well they will germinate.  As a general rule, seeds will last 1 year without a much special treatment but to extend that, you need to look at 2 major factors:  moisture and temperature.  If stored properly, seed viability can be increased significantly – it decreases by ½ for every 1% increase in moisture, and for every 5 degrees C increase in temperature – so the drier the better, the cooler the better – think dry, cool, and dark.


Keeping it dry:

  • use moisture-proof containers – that means you can submerge the container in water without water leaking in
  • decrease moisture by using sealed containers such as:
    • plastic bottles, Ziplocs, aluminum pouches
  • NEVER use a microwave oven to dry seed, use a conventional oven at low temperature – max 100F (37C) x 6 hours


Keeping it cool:

  • bear in mind that germination can actually begin from 7 – 15C (45-60F)
  • in general, store seeds in temperatures less than 10C(or 50F) – we use 3-5C (38 F)
  • perennial seed can be kept in the freezer to give them some vernalization time


Keeping it dark:

  • light exposure is less important to than the above 2 factors, but UV is thought to have a negative effect on seeds, so store them in a dark place. If you have your seeds in a Ziploc or other clear or light container, place them in a dark container to protect them from UV light.
  • If you keep your seeds in the refrigerator, that will keep them dark as well.


One other thing, physical damage also affects how seeds germinate, so handle them gently.