Most gardeners realise that hygiene is important, and this aspect of growing plants cannot be over-emphasised enough. Never reuse old potting compost unless sterilized, and always thoroughly clean and sterilize growing containers; an effective cleansing solution in which you should soak your seed trays and pots for about ten minutes can be made from 1 part chlorine bleach to 10 parts water. Do not forget to thoroughly clean you hands as well, your hands can carry viral, bacterial and fungal infection.

Germinating and raising seedlings.
In nature the first few centimetres of the soil surface tends to have all nutrients washed out of it by rain leaving it fairly infertile, this is why commercial seed and cuttings composts have very little if any fertiliser added to them, and it is important to keep this in mind when trying to germinate and raise seedlings. Nature has equipped seeds to overcome such problems, and it is necessary to try and mimic the natural conditions where our plants grow if we want to achieve maximum germination and success.

There are various media available for germinating and raising seedlings, ranging from the recently introduced Coir based Jiffy-7, through traditional Seed & Potting Composts, onto Vermiculite and Perlite. It is a matter of personal choice and deciding what works best for you.

By using Jiffy-7 the tiresome task of pricking out is avoided, and if the larger sized Jiffy's are used, healthy young plants can be raised ready for transplanting straight into the garden without requiring potting on. Jiffy-7 are supplied in several sizes ranging from 18mm to 42mm across, where for both small and larger scale use, Jiffy-7 help to reduce the amount of work required to raise healthy plants.

Most Garden Centres will be happy to help you decide which Compost will suit you and produce the best results.
 

The importance of protecting root ends cannot be stressed enough. Roots penetrate soil thanks to a mixture of carbohydrates called mucilage which are secreted from the root cap. British and Japanese research has demonstrated the importance of this mechanism for effective root penetration in compacted soils; when de-capped roots were compared with undamaged roots it was found that roots that had lost their end cap could be as little as half the expected length, whilst being a lot fatter.

Seedlings germinated in ordinary full or half trays cannot be left for too long before their roots spread and intertwine, when moving them to their new homes will cause root damage.

Starting seeds in full or half trays is a far more labour intensive way of growing plants requiring young seedlings to be treated with care so that they are not damaged at the pricking out stage. Your little plants should never be handled by their stems, they should be gently held by their seedling (cotyledon) or true leaves to avoid bruising their immature and vulnerable stems.

The plug method has many advantages, since young seedlings can be left for much longer before they have to be potted on. The individual cells in which their roots are growing prevent roots spreading and becoming tangled thereby allowing young plantlets to become better developed before moving them to their new homes, at which time simply pop the blunt end of a pencil through the drainage hole at the bottom of a cell to evict the young plant and drop it into its new home.

Cellular trays come in a variety of sizes from 12 - 60 cells, where the bigger the cells the longer plants can be left before moving them on. Using the 12-24 cells per tray size, plants can be left until they need to be transplanted to the garden.

Seed sowing technique:

The fewer the number of seeds you plan to start, the greater the number of seed starting systems available for purchase.  As you increase your seed starting plans over the years, more and more of those seed starting systems become inadequate.  The pots and trays that I use are suitable to the scale at which I operate, that is, the sowing of 300 to 400 packets of seed per year. There are recreational gardeners sowing anywhere from 1 to 2000 packets of seed per year.  At some point, you will discover the need to sow seeds in communal rather than individual pots, especially where considerable numbers of seed types need conditioning before germination. Therefore, the method I describe is peculiar to the scale of my hobby, and may not be suitable for many gardeners.  

After germination, the pots are moved to the proper location for growing-on temperature.  As soon as the seedlings have their first or second set of true leaves, depending upon vigour, they are transplanted to individual 2 1/4 inch seedling pots.  When the leaves of each plant begin to interfere with plants in adjacent pots, the seedlings are transplanted to 3 1/2 inch, then 5 inch, 6 inch, or 8 inch pots as necessary to maintain constant vegetative growth until it is time for setting out. Additional grit is applied as topping with each transplant to prevent the growth of algae and mosses, and to protect the crowns of the seedlings from excessive moisture. In climates where algal growth on the seed topping is excessive, you can use a product called Agribrom misted onto the topping at the rate of 15ppm. The additional medium added during transplanting to accommodate larger pots is the same germination mix through transfer to 3 1/2 inch pots. For transfer to larger size pots the additional medium added during transplanting is potting mix.  My potting mix is composed of 1/3rd germination mix plus 1/3rd compost plus 1/3rd garden soil. There are many variations of this practice for seed conditioning and special requirements.

After the first transplant, the seedlings need nutrients and trace elements.  The trays are watered from a solution which I make up in 1/2 gallon plastic bottles containing one half tablespoon of household vinegar and 1/8th to 1/4 teaspoon of general purpose fertilizer.  The purpose of the vinegar is to make a slight adjustment in Ph since my water supply tests out at 7.6 on average. Again, there are many variations on this practice based on the Ph preference of each type of plant. Seedling trays are moved to protected positions out of doors, under the carport, in the greenhouse, on the patio, etc. as soon as possible.

The following is excerpted from the practice of a popular nursery owner in Southern Illinois:

"I use Scott's Pro Metro Mix.  I sift it for seed sowing to remove the large bark pieces through a 1/2 inch screen.  Nothing added, unless I am doing alpines, in which case, I add 1/2 part grit.  My transplant mix is one part Metro mix, one part peat, 1/2 part vermiculite, 1/2 part perlite, and one gallon of silica sand for each  3 cu. ft. bag of mix.  For alpines, I add more perlite and some grit.

I use grit as a pot topping for seed growing.  One of the main reasons is to control the various fungal diseases grouped under the general heading of damp-off.  Seedlings come up through the grit easily, and since it dries quickly, and doesn't hold much moisture, the incidence of damp-off is much less than when using moisture retentive substances such as vermiculite or sphagnum.  It also helps to control the growth of lichen and moss under the lights.  I also use it on cuttings.  In addition, I use grit as a top dressing on those plants that dislike moisture around the crowns.  Most of those are rock garden plants.

If the seeds need light, just cover the post with a very light layer of grit, just until you can't see the soil.  For very fine seeds, such as begonia or campanula, I sow the seeds on top, then use a fine mist sprayer to wash the seeds down into the grit.  I also find it useful, when sowing like this, to sprinkle a very thin layer of white silica sand to help hold in moisture. Just as with other seed toppings, you can eventually tell by looking what pots need watering.  The grit does not stay completely dry, and as with soil, changes colour when the pots begin to get dry.  I find that the watering is on a much more regular basis with grit as a topping.  Almost all of the pots dry out in the same intervals.  I end up watering indoor sown seedling pots about twice per month.  I also mist them once a day with a mist setting on the hose sprayer to help break up the seed coats which sometimes prevent the cotyledons from getting free."

The following is the sowing procedure described by a nursery owner in Michigan:

"We sow almost everything in Sunshine mix which we mix with perlite, one part sunshine to two parts perlite. We fill flats in advance and water before we sow the seeds. All seed is sown directly on the surface and covered with a layer of chick starter grit, this goes a long way to prevent damping-off  problems. Sow on the surface and cover to several times the thickness of the seed with fine thick grit; with very fine seed, pots should be gritted first and the seed should be sown on top of the grit and watered down into it.

Keep moist but do not over-water. Fungicides are no substitute for good culture and in general it is best to avoid them. We rarely have damping-off problems and do not routinely spray fungicides to prevent it. Chick grit and care in watering is the best prevention. Be sure to use a thick enough layer to inhibit moss growth.

Difficult species are almost always best sown in a minimally heated white, not clear, poly-covered greenhouse. Easy species can be done under clear poly or fluorescent lights. White poly-covered cold frames should work well on a small scale, or better still build a small Nearing Frame. Seeds that need multiple 40-70 cycles are best placed in the refrigerator vegetable drawer in a ziploc bag with sunshine mix. This works better than baggies and towel for most species. We routinely extend the cycle time on the species Norm Deno lists as multicycle germinators. This is very helpful.

Freezing is seldom necessary or helpful, it will crack seed coats but there are better ways to do it. Freezing in household freezers is much too abrupt and may rupture membranes killing the seed. If you must freeze, place seed in a coldframe outdoors in the fall. Seed can be stored in the freezer for extended periods but only if the moisture content is very low. In general this is not recommended. Remember for many species extended dry storage is actually beneficial with old seed germinating much better than fresh seed.

Seeds requiring GA3 can either be placed on coffee filters soaked in the appropriate concentration of GA3 (1000 ppm is a good place to start) and the seedlings pricked off as the radicle emerges, or sown in flats and misted with a one time application. You can also soak larger seeds until they swell and then sow out. Keep concentrations as low as possible to reduce stretch problems.

We fertilize young seedling with a soluble balanced fertilizer at every watering (250 ppm total nitrogen) which is higher than generally recommended but the plants thrive on it. No burn problems at all, with a bit more fertilizer most plants will be more likely to out-compete the mosses which generally dislike high fertility media. Water until runoff and let flats dry out between watering. Beware of high pH In the water. We killed a ton of stuff due to this. We now adjust our water pH to 5.6-6.0 by injecting battery acid directly into the irrigation water along with the fertilizer. Buy a portable pH pen – it’s well worth the investment, pH-induced iron chlorosis is an insidious problem. Plants weakened by it quickly fall victim to fungus gnats and aphids. Algae and fungus gnat problems are also less severe if flats are allowed to dry out a bit, it's a very fine line.

Properly dry flats will be flattened when you water but show little sign of wilting before the water hits them, and will recover quickly with no tip burn. Be patient, the only thing to do with some species is to sow and wait for a couple of years. Don't kill shade-lovers by placing in full sun. Be careful of high light levels, even sun-tolerant plants may be sensitive as seedlings and it's easy to crispy the little ones. Many seeds will germinate immediately with the majority coming up a year or more later. Often the early germinators turn out to be the weakest plants. We often weed out the early stragglers to wait for the main flush of germination. Don't throw away seed pots for at least four years on the long germinators. Before you trash a pot dig around and find a seed and cut it in half -- if it hasn't rotted then it will germinate eventually.

There are many formulas for success but the most important ingredient is patience. Don't let your seed pot dry to dust, and don't let them get soggy and moss covered -- if they do carefully cut off the moss layer leaving the seed behind and regrit and wait some more. It in doubt about what to do, think about what would happen in nature and try to emulate it. This is a great help in determining whether to start cold or warm."