Seeds at the Henry Foundation

That time of year again, seed sorting for the Hardy Plant Society at the Henry Foundation.  It's a fascinating place, that was founded in 1948 by Mary Gibson Henry, an avid botanist and plant explorer,  who collected native plants from remote areas of the West, Midwest, and Southeast United States and replanted them on her 30 acre estate in Gladwyne.  Less than 10 miles away Laura Barnes was creating her arboretum, but the two women seem to have had little contact with each other.

The  Foundation is now run by two of Mary Henry’s nieces and each year host the Hardy Plant Society's seed sorting days -- this year it has been a nightmare scheduling it because the long drive to the house has been under snow and plowing is sporadic.  The seeds distributed are donated by the Plant Society's members and always include some rare and wonderful gems.  It's hard for a novice to jump in -- the seeds do not come with packet instructions and I've found germination rates really temperamental.

The basics of seed germination are essential to get right:-

1.    Temperature    A steady constant 73 degrees F is best for most varieties. Large fluctuations will impair germination rates, heating mats are ideal, the top of your refrigerator are usually very suitable for seed growth.  Once the seeds begin to sprout move to a sunny location or under lights.  Most seed failures are a result of incorrect temperature.  Buy a cheap thermometer to monitor it.

2.    Moisture    Water has to enter the seeds for germination to start.  Once this process has started water requirements are minimal and more seedlings die by over-watering than by under-watering.  If temperature and lighting conditions are correct one or two waterings are sufficient for seeds to sprout.  Adding a drop of dishwashing liquid to the water helps absorption, warm water is absorbed faster.  You can either bottom soak or mist the seeds.  Cover with transparent plastic covering to allow light and prevent evaporation.

3.    Light    Some seeds need light to germinate, some will not germinate unless they are in the dark.  Once they have germinated light is vital for all seedlings.  If you are getting a jump start on the season and sowing indoors there are various options.  A bright windowsill (but not in direct sun which will fry the plants) will work, but make sure you turn the seeds to ensure even light.  You can make a simple frame with pvc pipes and hang cheap fluorescent shop lights with S hooks and chain.  This way you can raise the lights as the seedlings grow, maintaining a gap of 2-3” between the seedlings and the lights.  Expensive growing lights are not necessary, but it is important to replace the bulbs every year as the strength of the light dims even if this is not noticeable to our naked eye.  Buy a cheap timer and leave them on for 14-16 hours.

4.    Soil    Soilless seed starting mixes are sterile and formulated to retain water, allow air penetration and maintain the low pH most seeds prefer.  To commercial mixes add 1/3 additional perlitte to improve drainage even more -- be careful not to breathe in the perlite dust.  Place on top of the soil mix a thin layer of spaghnum moss to help keep the planting medium sterile and prevent damping off.  If you seeds do not want light for germination (information can be found on seed packets or on the internet) scatter seeds over the spaghnum moss and then top with a layer of traction sand (coarser than builders sand) or very fine gravel -- this helps drainage and stops the soil being washed away when watering.  If the seeds need light, sprinkle on top of the sand layer.

5.    Scarification    The key for successful germination is for water to penetrate the seed.  Some seeds extremely hard seed coats which make penetration more difficult.  To over come this you can soak the seeds in water overnight, nick the seed coat with a knife or simply rub the seed over with a file or sand paper.  Be careful not to go too deep and damage the embryo.

6.   Stratification    This is the process of exposing seeds to a cold moist environment for several weeks before planting.  Some seeds require a period of cold to germinate well -- this requirement is a safety mechanism which allows tiny seedlings a whole growing season before they have to survive a cold winter.  To fool the seeds into thinking they have gone through a winter, place the seeds in a plastic bag with some moistened vermiculite and leave them in your fridge for two to three weeks.  Make sure you open the bag a couple of times to ensure they have some air exposure.

7.    Seedlings.    Once your seedlings have developed true leaves either cut off the weaker ones with scissors to prevent overcrowding (don’t pull out as this disturbs their roots) or prick out the plants.  Gradually aclimatise them to their new surroundings, as moving them to a coldframe or outdoors if the weather permits will be a shock.  Make sure you label the seeds carefully when you plant them, with both name, date you planted them and any other requirements.  A #2 pencil works best for this.