Selecting a phenotype from seed


If you have multiple seeds to work with, and particularly if those seeds possess a high degree of phenotypic variation, you may wish to consider selecting certain individuals so that they can be kept as mothers, to provide cuttings for future crops for years in the future.

Setting up your equipment

You will need seeds, pots, soil (or whatever your chosen substrate is), lights (cool CFL or LED lights are preferable for young, tender seedlings), distilled or RO-filtered water, and airflow. You may also wish to use a light vegetative growth solution (not at first: until the first true leaves have appeared, your seedlings should be fed nothing but distilled/RO water) and root stimulator to give your young radicles (primary tap-roots) the best start in life.

Some growers germinate their seeds in distilled water, while others simply sow seeds directly into well-watered substrate. However, many growers prefer to use the saucer method, which entails placing seeds on moistened tissue and containing them within two saucers. This technique is highly effective, simple to master and presents little risk of harming your seeds. A full guide to the saucer method can be found here.

Caring for your seedlings

Once your cuttings have rooted and vegged for a week or so, start the flowering cycle

Once your cuttings have rooted and vegged for a week or so, start the flowering cycle

Seeds should be sown into small pots at first, and transplanted (roughly every 7-10 days) as they begin to outgrow their pots. Soil/substrate should be lightly packed, but not so compacted that drainage (and growth of young roots!) is restricted. Lights should be set low over your pots and raised as necessary.

A good rule of thumb at this stage is to keep temperatures around 25°C/75°F (if germinating your seeds in water, warm it to this temperature first, and try to maintain it!) to accelerate germination and initial growth. Many growers and breeders argue over the correct RH for germination, and it often depends on the strain, but generally, sticking to the 50-70% range is advisable.

Taking cuttings from your young plants

After the first two weeks or so of vegetative growth, your young mother plants should have developed sufficiently that they can be pruned (around halfway down the central stalk, immediately above a set of side branches—which will then become the primary branches).

The sections that you have removed should each yield at least two or three usable cuttings, which can then be rooted and flowered so that you can determine their characteristics and make your ultimate selection. Make sure to label all of your clones so that you do not lose track of which mother plant they came from!

Root your cuttings in the usual way, and allow them a week or two of vegetative growth before switching your lighting regime to 12/12 to induce flowering. Some growers would argue that there is no reason not to switch your lighting regime as soon as the clones have rooted and begun to put out visible new growth; however, in order to allow flowers to develop to their full potential, it helps to develop a strong central stem and primary branches first.

Throughout the process, ensure that you maintain your mother plants with the utmost care and attention. For more information and tips on maintaining healthy mothers, check out our handy tutorial.

Choosing your desired traits

As your cuttings flower, you can begin to analyze them for desirable traits. Initially, look for traits such as internodal length, speed at which flowering commences, and general health and vigour. Ideally, for indoor growing you generally want short internodes and rapid commencement of flower formation (which is why indica genetics are present in practically all indoor strains). However, many sativa strains have long internodes and flower relatively slowly, yet are desirable for their own specific reasons such as flavour and cannabinoid content.

As flowers develop, you can look out for special plants and mark them for selection

As flowers develop, you can look out for special plants and mark them for selection

As flowers develop, take notes on the quality of the aroma, the structure of the buds, and the overall condition of the plants. If high humidity is an issue, you may wish to focus on plants with loose, light bud structures, rather than the dense nugs that can allow mould spores to penetrate with ease. Look out for plants that show signs of stretching, deformation or infection, and discard those.

For the most part, you should be keeping your flowering cuttings in typical growing conditions. However, for selection of specific traits, such as resistance to mould or drought, you may wish to introduce environmental variables such as high humidity or reduced irrigation. If conducting your selections outdoors, this is as simple as growing the seeds in the environment that they are intended for and seeing which ones come out best; indoors, you can tweak your growing conditions as necessary to mimic various outdoor habitats.

The ultimate test of your selection comes once it has been harvested, dried and cured, and is ready to sample. At this stage, you can make a final judgement on flavour, aroma, trichome coverage, and effect. Then it’s as simple as discarding the losers from your mother plants, and taking as many cuttings from the winners as is needed for your next crop!

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