To obtain numerous plants which will not have the exact appearance of the parent or its siblings, sexual propagation is the easiest and least expensive method.
For seedling generation, the following steps can be followed:
Seed Provenance
Provenance refers to the geographic location from which seed is collected. Provenance may influence traits such as hardiness, growth rate and adaptability to climatic conditions. This should be kept in mind when purchasing or collecting seed.
Seed Collection
A saying goes, ‘Initial steps are harder to take’, knowing when to collect the seeds that are ripe and ready to harvest, is the crucial step for nurturing the future.
Make sure to keep up a collecting calendar over several seasons to not lose out the seeds that spill in a short time after maturity(foam flower, fire pink, blood-root and wild geranium), while others produce mature seeds in late summer or fall.
In general, the fruiting structures that hold the seeds will give indications that the seed is mature. Most capsules, pods and berries will expand in size and turn from a light to a darker color. Likewise, the seeds themselves usually turn a darker color when ripe.
Do not leave seeds in a plastic bag for any length of time because they will begin to rot from humidity.
Seed Cleaning
Once the seeds are collected, spread on clean paper for several days to dry, under low humidity and proper air ventilation- it often allows the fruit to split open for easy seed removal.
Some of the field collected seeds impose a threat of infection. Fumigation of stored seeds or placing a Non-Pest strip in seed bags is the best way.
Other means of getting rid of seed capsule/ pods are by shaking the seed bag vigorously; beating the seed heads into containers, such as a bag or bucket, or using a rolling pin or mallet.
Fleshy or moist fruiting structures, soaking them in water overnight to soften and then peeling the pulp off the seeds with a finger or gently mashing them with a wooden spoon holds good.
Seed Storage
If the seeds are not properly stored, there are great chances of losing their potency to germinate. Seeds should be totally dried before storing- to prevent any fungal growth and possible germination, then a small amount of Silica Gel in a porous wrapper, that’s placed in the bottom of the container to draw moisture from the air and away from the seeds.
Dry seeds are to be stored safely in room temperature for the time being. But for the longer duration, seeds lose viability in direct exposure to increased moisture or temperature, or both. Refrigerator storage with temperatures of 34-41 degrees F will do good. Cool temperatures slow down speed metabolism, extending the life of the seed.
The seeds produced in moist, are layered in damp medium in airtight containers and refrigerated, being kept viable to prevent them from entering an extended period of dormancy.
Store the seeds in sealed envelopes, canisters or jars marked with the name and storage date.
Seed Sowing
While sowing seeds in pots, flats or other containers, use containers that are at least three inches deep filled to the top with potting medium. The containers full of soil should be moisture not damp. Spread the seeds uniformly throughout, allowing ample space for root development and sprinkle adequate water in a timely manner.
A good rule to follow is plant the seed to a depth four times as deep as its length. The larger the seed the deeper it should be planted, for smaller seeds they should be barely covered with soil.
Always use Sterile Medium to discourage fungus and disease which are available at regional garden stores.
Seed Germination
Only when certain physical and chemical requirements are met, that the seeds start sprouting out.
Many seeds will germinate under a wide range of conditions:
- Time
Proper timing is an important factor to most seeds, may it be the state of dormancy or germination. The few which sprout immediate after shed need to be taken care off and more likely scarification is required. - Temperature
In order to germinate, seeds are well stratified under 35 to 50degrees F. In 55 degrees, the stratification will take longer time to complete and in between 70-80 degrees F seed germination is best proceeded. - Light Exposure
Some seeds contain a light sensitive pigment, Phytochrome that often speeds up germination. Energy obtained by absorbing different wavelengths of light renders the phytochrome molecule active or inactive in promoting growth. - Carbon dioxide and Oxygen
In a water saturated soil, seed germination cannot take place. Though oxygen is required for the respiration of food reserves in seeds, the carbon balancing is a key feature. The abundant water diffuses little of oxygen in and much of carbon. Tacit care must be given for oxygen-carbon balancing. - Seed Coat
In order for the seed to germinate successfully, seedlings need to penetrate the seed coat first. Some offer less or no resistance while some require scarified or acidic fruit acid to break down before absorbing water to swell. - Germinating Hindrance
The toxic by-product remnants in the grow area hinders the growth of new seedlings. Tannins, phenolic compounds or alkaloids from roots or leaf and stem litter are the one such set-backers. - Hormones
Hormones needed to break down these inhibitors in seeds, and such hormones are often known as Gibberellins and the Cytokinins.
After germination, seedlings generally remain in seed flat for 4weeks and then 4inch pots for 5-6weeks, and then seedlings can be planted outside at the beginning of the frost free period in spring.
For seeds planted in February or March indoors, the seed containers can be placed in a sunny, south facing window in order to get 6-8 hours of direct light per day. A constant soil temperature of 70-78 degrees F is best for rapid, uniform germination.
For seeds planted in a cold frame, it must be pulverized to a depth of 6inches and mixed with a 3-4 inch layer of peat moss or coir peat or ground pine bark. No fertilizer is needed.
When sowing is completed, water the soil in the frame with a soft, fine spray. Cover the frame but tilt the cover to allow fresh air to enter. Keep the soil constantly moist, neither too wet nor too dry. When the seeds have germinated the first set of true leaves is enlarged, transplant the seedlings to the garden, for them to harden off. By following the above processes, seedlings can be grown in optimal conditions.