Germination of seeds

Germination of seeds is certainly a topic in most gardeners’ minds at this time of the year.  In fact, while I was cleaning out my old pots and collecting seeds to plant, my mind wandered to wonder…wondering how the tiny, hard seeds can indeed produce shoots to become wonderful and inspiring plants from something that almost seems dead.

group pf germinating seeds

group of germinating seeds

A seed surely looks lifeless as it displays no obvious signs of life rolling around in its package.  According to several articles in fact even biochemical tests for metabolic processes such as respiration, show very little to indicate whether the seed is alive. Of course for us the seed collectors, we hope the seeds have been stored correctly so they are not dead, but merely dormant.

 

Dormancy

 

While all living seeds are inactive, awaiting hydration, some require specific environmental conditions which generally mean a longer time before germinating.  In the case of home germination of seeds, gardeners need to know what those conditions are, as generally stated on seed packages or by checking out good sources of planting information.

Common vegetable garden seeds generally lack any kind of dormancy and are ready to sprout with some moisture and warm enough temperature for their biochemistry to begin. Many flower seeds and those from wild plants in particular may have deeper forms of dormancy that require further conditions before their growth is triggered.

While we may be familiar with scarifying and stratifying, both terms that describe external treatments   of a seeds outer membrane that some seeds require to leave their dormant state, temperature, and light also play a role before hydration can begin.  There are also physiological factors that signal the end of dormancy, such as plant hormones of Gibberellins which activate plant growth.  Other seeds may have a naturally found coating of Abscisic Acid which prevents germination until environmental conditions have worn this layer off and provided the conditions for germination of those seeds.

Germination

 

Germination can be explained simply with a few brief diagrams, or in great detail with many technical terms. When I bought seeds recently and began to collect pots and planting materials, the gardener and biochemist in me wondered how a few molecules of water and some sun could cause the tiny speck of a seed to ultimately form a large, beautiful plant.

Regardless of its size, each seed contains an embryo and in most cases, a store of food to help that seedling begin its formation.

Avocado seed diagram

Avocado seed diagram

 

A “typical” seed   has fundamental parts:

  • a seed coat
  • a storage area (in this case the endosperm which houses food and genetic material)
  • a dormant embryo

 

The embryo has three parts:

  • the cotyledon (or seed leaf)
  • the epicotyl (becomes the shoot)
  • the radicle (becomes the root)

 

456px-Salix_scouleriana_seed

 

 

 

Physiology of Germination

 

When water penetrates through the seed coat and begins to soften up the hard tissues inside, causing the seed to swell up and then split.  Then water enters even faster and begins to activate the biochemistry of the dormant embryo.   Once such substance activated there is Gibberelli Acid (GA), which is a plant hormone similar to steroids.

Then the GA is carried with the water through out the seed tissues and in to the endosperm until it activates genes inside the seed and a complex DNA/RNA reaction takes place. Basically this “blue print” allows the genetic characteristics of the parent plant to be passed on through the seed. Also as this is going on, the embryo feeds on the starch and sugar found in the endosperm as well.

Under proper conditions, the seed begins to germinate and the embryonic tissues begin to protrude from the seed’s casing in the form of what is called the Radicle. This primary root anchors the seedling in to the ground as well as absorbing more moisture.  From here other growth takes place, but the components vary.

In most plants another shoot emerges, many of which have three parts:

– the embryonic stem called the hypocotyls

– the cotyledons ( first leaves)

– the epicotyls

 

 The hypocotyls

The hypocotyls grows out and lifts the growing seedling up as it becomes the stem of the seedling and carries the cotyledons (embryonic leaves)   clear of the ground.  At this point growth components change depending on the classification .Flowering plants are classified in to two groups, depending on whether they have one or two cotyledons.

The cotyledons

Monocots have only one single shoot or cotyledon after the seed breaks out of the ground. In these plants the roots develop from the stem instead of from the base of the embryo. Included in this group are flowers such as orchids and lilies as well as wheat, onions and corn, asparagus and many other plants and grasses.

 

 

Monocot diagram

Monocot diagram

 

Dicots have two initial leaves or cotyledons that grow from the embryo.  Then the the epicotyls forms the initial stem which holds up the true leaves, while the radicle grows and forms the plant’s the root-system. Most flowering plants found in the garden belong to this classification. Beans are also a dicot.

 

 

Dicots

 

The epicotyls

The epicotyls, which are above the cotyledons and below the plants real leaves, are not found in every plant. Where they are present, they become the plants stem, which rises up and gives way to the plant’ s further  leaf and stem development. The growth of plants is another matter that requires far more complex physiological terminology than this author/gardener can explain.

 

Germination of seeds

 

In addition to Monocot and , Dicot germination there are other forms including but not restricted to Epigeous, Hypogenous and Precocious germination. There are many names, classifications, conditions the seed requires and other complexities that my brain can barely contain!

Despite that, germinating seeds each spring is part of my celebratory ritual and I am glad to have some basic understanding of what really is going on inside each seed.  Based on several definitions, seed germination is said to have occurred when growth of the radicle bursts the seed coat and protrudes as a young root… but to us gardeners the no names matter as the excitement builds when the green shoots poke their heads above the ground and inspire us to bury more seeds for germination!

 

-_Seedling_-001

 

Indoor seed growing

Indoor seed growing is always a joy for many reasons, not the least is that it means winter is nearing an end and spring is not far off. Of course there are many lessons learned each year as we try new seeds and new techniques that often do not yield the results we hoped for. Personally speaking, despite any setbacks…soggy seedlings and all, I still find it so inspiring that so much life, joy, beauty, food and medicinal elements come from such small seed.

There are a few basics that can help the novice who wants to start indoor seed growing and of course there are countless articles in magazine, books and on-line. Please take the following information as a starting point…off you go now, as there are countless seeds to plant.

 

sunflowerseedlings_1

Choosing Seeds:

Before choosing seeds, remember that the soil and lighting conditions of your garden need to be considered, just as you would when purchasing live plants. The light requirement of the plants after germination is generally shown by a symbol on the seed packages of a sun for full sun through to a cloud for full shade.

Seed sources are everywhere from floral departments of large grocery stores, garden centres, hardware stores and even big box department stores. Of course dreaming our way through local seed catalogues is marvelous fun and gives the widest variety of choices for annuals, vegetables and even perennial seeds. In addition, the great photographs, detailed planting and maturity information as well as many new hybrids not available in stores, makes these companies a great source!

 

Getting ready for Spring

Getting ready for Spring

If you belong to a horticultural society or garden club, you are probably able to participate in a seed exchange for a good source of vial seed as well as information on the plants themselves. For those on their own, perhaps others in your neighbourhood have seeds to share or swap. Remember, once you have a hearty plant you love, whether grown from seed or purchased full grown, you will have all the seeds you need for next year’s growing season.

Annuals and vegetables are generally the easiest to start indoors as their germination requirements are quite straight forward. Perennials on the other hand may need stratification or scarification before germination can begin. Stratification is a cold period required to break the seeds dormancy, which can be achieved by a few weeks in the refrigerator before planting, or by planting directly in to the garden bed near the last frost date. Scarification is nicking or sanding through the seeds tough outer coat so the moisture required for germination can get in.

 

Seed Planting

Follow Directions:

Seed packs will contain a great deal of information on the plant itself, including the light requirement as mentioned, and length of time for flowers to bloom or vegetables to harvest. With new varieties of both available, even maturity times have changed so reading the packages is always important.

 

Perennial seed instructions

Perennial seed instructions

Annual seeds best started Outdoors

Annual seeds best started Outdoors

Further information on planting depth, times, light requirements, and growing temperatures are provided to ensure you have optimal germination. In addition, specific details for more challenging seeds would also be listed. An example of this would be for seeds requiring light to germinate so you not cover them with soil, while others might need soaking, scarifying or stratifying. Plants that do not transplant well will also be indicated and these seeds should only be planted outside once the danger of frost is past.

Word of warning: If you plant too early, the seedlings and young plants may become spindly and overgrown, despite good sunlight or strong grow lights!

 

Planting Media:

While regular potting soil can be used but as it can be heavy when wet, soilless mix is recommended. Jiffy pellets, which are peat moss compressed for ease of storage and use are readily available both in kits and often priced per piece. The advantage of these media is their inexpensive prices and that no containers are needed as the mesh around them ensures they retain their shape even in the wet, expanded state.

Jiffy pellet kits are readily available in most types of stores selling seeds as they hope to encourage customers to try their hand at indoor seed growing.  There are many brands of soilless mix available at garden centre and many easy recipes for mixing your own.

As it has now been determined that peat Moss is not an infinitely available resource, grown coconut fibre or compost can be used instead with the addition of compost.

Basic Soilless Potting Mixes              

  • 4-6 parts Sphagnum Peat Moss
  • 1 part Perlite
  • 1 part Vermiculite

OR

  • 4 parts coconut coir
  • 2 parts compost
  • 1 part Vermiculite
  • 1 part perlite

 

Coir is a natural fibrous material extracted  from coconut husks, which are the byproducts of other industries  that use coconuts for food products. In addition to many commercial items manufactured from these harvested husks, they are also used in horticulture.Frequently labelled as Coco Peat , this product is commonly available in gerden cnter as are vermiculite and perlite.

Coir or coconut husk segregation

Coir or coconut husk segregation

 

Coco peat is recommended as a substitute for shagnum moss (peat moss), because it is free of bacteria and fungal spore, and produces good results without the environmental damage caused by peat mining.

Coco peat is usually shipped and sold in compressed forms of bales, briquettes or discs which expand up to more than ten times their weight after  the consummers add water.Unfortunaley while it is a great produce to hold moisture, it is low in nutrients and can compute for nitrogen in the soil,  so when used as a soil additive compost or other slow release fertilizer should be added.

Containers and accessories

There are a wide variety of containers you can use  for indoor seed growing, from small flower pots to any container with drainage holes (cell pack, pots, jiffy pellets, Styrofoam coffee cups, food trays etc.). Remember if reusing containers, to wash with them soap, water and a little bleach first and then rinse them very well to ensure any fungus, bugs or bleach is long gone!

 

old pots before washing

old pots before washing

 

In addition you would need trays to hold those containers, plastic covers or domes to keep the moisture in and labels to ensure plants are properly identified. Of course you can use the clear lids of takeout containers or even clear plastic veggie bags held above the seeds. I have found popsicle sticks wedged down in the corners of a small container works fine and I remove it once the seeds have poked out of the growing media.

Theses sticks can also be used as labels there or if broken off and placed in front of where you will place a specific seed. One drawback to these is that ink can run on the wood. You can buy plastic plant labels or even cut up margarine lids. There are many ways money can be saved and items reused and indoor seed planting is no different.

 

Planting:

Fill the containers with your sterile planting media and moisten the mixture so it feels like a damp sponge about an hour an hour before sowing to let the water penetrate evenly. While wait you can collect all seeds and planting devices as well as go over the seed planting information to ensure you have soaked, scarified or stratified the appropriate seeds.

The most difficult thing about planting seed is getting the right depth especially for the smaller seed. In addition, the smaller seeds almost seem to disappear so for those a planting aid helps. There are small plastic seed holders available that have a tiny opening designed to let small seeds out one or two at a time. For the handy minded person, a small envelope can be sealed and then a tiny hole poked in the end, allowing seeds out.

 

Watering:

Your newly planted seeds need to be watered lightly from the bottom of the pot or by using a spray bottle to ensure the seeds are moistened but not disturbed. When they are moist, cover them with a plastic dome and place them in a warm location to germinate. Other options for speedier germination are placing them on top of the fridge, under grow lights , safely by a warm heat source as they germinate best between 18 – 24°C. In fact, there are temperature controlled heating pads specifically designed for this purpose which are available in kits or individually at most garden centres.

Once germination has take place, make certain the dome or clear plastic cover is unsealed to ensure good ventilation and prevent fungal growth in the soil. Fungal buildup, called damping off can cause seedlings to turn black at soil level and die overnight. In the past I have had this issue when crowding pots and pellets too close together which also blocks good airflow.

Prevention is best, but antifungal products are available, and seedlings could be sprayed with commercial fungicides Mycostop or Captan , but there are healthier herbal remedies you can use. A home remedy that apparently prevents this as well is a one dusting of ground cinnamon on the soil surface.  A Chamomile tea infusion of 3 tea bags soaked for about 20 minutes can be lightly misted over the seedlings.  Garlic as well is known to be a natural fungicide, so mash up several cloves and boil then in about an inch of water and water in to the seedlings once cool.  Of course good spacing and even a fan can ensure better air movement, no matter where you have the seeds growing.

Once the seedlings get an inch or two high, you can remove domes or covers completely, but keep an eye they not get too dry either. Water lightly still, once the soil begins to look dry.

 

Light:

Seedlings love light, so if you only have a few, placing them on a sunny window ledge should do the trick. For many of use with limited light and a seedling urge that is hard to control, grow lights are a good option. There are light stands, small lamps and many fixtures where grow light bulbs can be used instead of regular fluorescent tubes. Again, a much needed field trip to a garden center is a must, at least to research your options!

Grow lights or cool fluorescent lights work best and now there are a few frequency options such as natural, wide range and those designed to simulate sunlight. Ideally optimal amount of light for your seedlings under lights are 16 hours on, 8 off. And the lights should only be 4-6 inches above them to start. Remember, whether your newly sprouted plants are under lights or in a sunny spot, leggy seedling are an indication that the light is inadequate.

Transplanting & Fertilizing:

After the seedlings have formed their second set of leaves they can be gently transplanted in to individual pots. In addition, feeding them a general balanced water soluble fertilizer of 20-20-20 at approximately ¼ strength once a week, is recommended for good growth. Gradually increase the strength over the next few weeks as you prepare to harden the new plants and move them outside.

 

Hardening Off :

 Before you move the young plants in to their final containers, or in to the ground of your garden, they need to adjust to the outside conditions they will call home. This process, which is called our seedlings into containers or the ground outdoors, it is essentially to “hardening off” is a gradual period of acclimatizing which ensures a good survival and growth of the once tiny seedlings.

 

As the light intensity, temperature outdoors, wind etc. is much different than what they were used to inside, begin  by moving the trays and containers out in to a shady, protected area  for a couple of days . Then gradually extending the stay and moving them over a week to ten day period, to where they get their ideal light, soil and temperatures needs.