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Starting Seeds Indoors

Giving Them A Head Start

Gardeners in northern climes use a variety of means to cope with the brevity of their growing season. When the last frost might arrive as late as May or early June, seed planting must be delayed also. With some quick-growing plants, this isn't too much of a problem. But many vegetables and ornamentals will benefit greatly from a little head start.

Starting seeds indoors can be an imperative for certain plants in particular climates. Even as far south as Washington, D.C., where we reside and where the last frost usually arrives in early April, getting an early start can make a big difference.

What follows is a guide to help you shorten the learning process a little. After you've done it once, it will seem easy and routine. I'll begin by breaking the whole operating into its basic components.

Note:Remember as we go that seeds and seedlings are two different things - so you'll have to treat them differently.

What Seeds Need In Order To Grow


The first step is to make sure you've got an appropriate growing medium for your plants. Inappropriate mixes get adobe hard after a few waterings. Your mix has to stay light and pliable. You may be able to find a good quality potting soil mix locally. These ingredients are available at most nurseries. Such ingredients are very light and hold moisture well. They have little nutritional value, but seeds contain the food they need to germinate.

What will you put your planting mixture in? Cut-off milk cartons, deep-sided disposable aluminum pans, special seed-starting systems, all will serve. They'll need at least three inches depth for roots to grow, and small holes for drainage so those roots won't rot. Many gardeners prefer to make their traditional wooden flats (14" by 12" by 6" is a good size). Leave about 1/8 inch gap between the bottom boards so extra water can drain out, and then cover this base with newspapers or a thin layer of leaves to keep the soil from draining out.

Note:Some gardeners grow seedlings in two indoor growing stages. They start them in one flat and then transplant them to another roomier flat for a few weeks where seedling roots will have more elbow room to grow on before final transplanting into the garden.


Many seeds are native to tropical or subtropical regions and are genetically programmed to grow only in reaction to warm soil temperatures. Generally, seeds germinate better if their soil (not air) temperature is constantly 70° F or above. Keep your seed trays in a constantly warm place but check them daily for drying out.

Maintaining consistently warm temperature both day and night signals the seeds to begin growing. Probably no other factor will speed up germination time more than a constant warm temperature. Adding a consistent heat source will help guarantee you impressive germination success.


Seeds also need to be kept constantly moist in order to germinate. Two key words here: constantly and moist. Never let that soil dry out. In other words, you want the mix moist, but not too wet.

Note:The consistency of a just wrung-out sponge is about right and a good standard to use for a moisture gauge.

Moisten your soil thoroughly before you sow, mix it well to distribute moisture evenly, and be sure it doesn't dry out afterwards. One easy aid is to drape a sheet of plastic wrap on top of newly planted seeds to keep moisture in. Be sure to check every single day to see if any seeds are starting to sprout. If they are, immediately remove the cover so they can get some air circulation. Be sure to water as often as needed from a plastic spray bottle or a watering can with a very fine, upward-pointing rose so the drops will very lightly fall on the soil. If you have a plastic cover on the seedling tray, lift it up to water, then lay it down again. Check often. Your water should be at least room-temperature warm.

Note:Don't just pour water on top of your un-rooted seeds or they will wash right out of the soil mix.


Most seeds don't need light to germinate. This applies only to germination or sprouting stage; right away after the seedling appears above the soil, light is a necessity.


Fertilization is not necessary for seeds as they carry their own food inside their shells and have enough food energy to germinate on their own. Young seedlings, on the other hand, will need a weak fertilizer to grow successfully. (More on this later.)

Sowing Your Seeds


In addition to containers and soil mix, you'll need to have some clean Popsicle sticks, strips of stiff plastic, old-fashioned plant labels and a pen with indelible ink to write the plant name, variety, and date sowed. Don't skip this step. If you neglect to label your flats, you'll be surprised how quickly you lose track of which seeds are which and when you planted them.


It is important not to start seeds indoors too early. This is generally four to six weeks after planting, when they have at least two sets of true leaves. In other words, if you're aiming to plant the first week of May, you probably shouldn't be starting seeds any earlier then mid-March. Sowing your seeds at the proper time indoors allows them to grow into robust seedlings ready to plant out in the garden when outdoor weather conditions are right in the spring.

Fill your containers almost to their brims with moistened soil. Tamp it down and smooth it out. Then begin carefully setting your seeds in. Plant them shallowly - some seed packets tell you how deep to sow your seeds, so be sure to read them carefully.

To keep better track of where you've planted, you may want to set all your seeds on the surface of the flat and then sift extra soil mix on top to cover them.

If you're using individual containers, you'll want to put only a couple of seeds (the extras are for insurance) in each container. With flats, you'll want to space your seeds a half-inch apart if you intend to transplant them to a second, grow-out flat later, or one to two inches apart if you're going to keep them in the same flat until garden time.

It's always best to plant more seeds than you think you'll need. They may not all germinate, and it's best to have many seedlings so you can choose only the healthiest and thin out the smallest and weakest ones later. If you end up planting more than one type of plant in a tray or flat, choose ones that have about the same germination time and transplant date.

Note: Again, read the packet backs for this information. Don't forget to label each variety as you sow the seeds.

What Seedlings Need In Order To Grow


The very first thing you need to do for those sprouted seeds is give them light. Lots of it. Otherwise, you'll end up with wimpy, leggy, pale weak seedlings that will never grow into robust usable plants. Some people manage to give their baby seedlings enough light by putting them in the home windowsill, but it's not recommended and really doesn't work very well. If you are determined to try it, be sure to rotate the plants every day or so (they'll grow toward the window), and try setting up white or tin-foil reflectors around the sides of your containers to bounce more light onto the plants. Be sure the windowsill doesn't cool down drastically at night (a common problem).

Note: Plants that don't have enough light will grow up weak, pale, leggy, with long stems but few leaves and a dismal future.


You kept your seeds constantly moist; but once your seedlings are up and at 'em, you want to moderate that a bit. Begin watering them slightly less often. Once seedlings are at least a few inches tall, it's OK to let the top half-inch or so of soil actually have a chance to dry out between waterings. Check daily but putting your index finger into the soil - actually using this finger test to see how moist soil is works best; it's hard to tell from just looking, even for experienced gardeners.

Too much moisture encourages root rot or " damping off," the infamous fungus that can fell your seedlings right at ground level.

So water a little less frequently, but more deeply when you do. Again, use the finger test to see if water has penetrated deep enough.

You can also discourage the damping off fungus by making sure the air around your plants is circulating well instead of stuffy and stagnant.


Seedlings can grow well at air temperatures between 65° and 75° . They don't require that same incubator environment that seed germination did.


Seeds don't need food while germinating because they contain their own food, just like an egg. But seedlings will rely on you, just as chicks do on their mother hen. Start giving them some liquid nutrition. Any good all-purpose fertilizer such as Rapid Grow™ or Miracle Gro™ will do fine. Of if you prefer an organic feed, fish emulsion works well (but is a little odiferous). Seedlings are delicate - begin by applying fertilizer only at a half strength concentration. Feed seedlings once or twice a week. As they get bigger with several sets of true leaves, you can up the dose to full strength: according to the manufacturers directions.

Note:Proper fertilization is crucial or your seedlings will not be healthy. Moderation works!

Thinning Is Critical

Please don't neglect thinning out your seedlings, keeping only the best specimens. Do this by using a small scissors and snipping off the weaker and excess seedlings at soil level. Don't just yank them out as that disturbs the roots and soil of the plants you're planning to keep. Thinning is a critically important step. It's hard for " first timers" to discard seedlings nurtured so carefully, but please do learn to do it! Over-crowded seedlings always develop into inferior plants never likely to succeed in the garden. Their roots become intertwined and crowded so you can't separate individual. plants; they are much weaker and more disease prone and without proper room and nutrient uptake they end up with leggy stems and sad, pale leaves. Save yourself a lot of grief by thinning and spacing seedlings properly as soon as they have a set of " true leaves".

Indoor Transplanting

As I mentioned earlier, many growers transplant their young seedlings to wider spacing in new growing trays once they have developed their first true " regular" leaves (the first two leaves that appear are the baby or " seed leaves" ). There are a number of advantages to this. It allows you to start a lot of seeds, then thin them out to keep only the best ones. The transplanted seedlings will have all the room they need to grow and thrive and won't be stunted because of overcrowding should the weather not be ready when they are big enough to go outside into garden soil. You'll need one container for seed starting and baby seedlings, and another deeper one (4-inch pots) with more fertile soil for the transplanting stage.

Damping Off Fungus

Avoiding The Fungi

It is essential that the soil you use be sterile. One of the great bane's of seed growing is a fungus commonly known as Damping-off Disease. The spores of this fungi are ever present in soil and the conditions of indoor gardening seem particularly advantageous to its propagation. It can wipe out hours of hard work in a matter of days.

To avoid this scourge you must use a sterile soil or, even better, another sterile medium. Some gardeners like to use their own soil. This involves sifting out any larger clumps and stones and then sterilizing it in an oven. This is a lot of work and the results are probably no better than using a commercially available starting medium. These usually consist of some combination of vermiculite and peat moss and are often referred to as "soil-less." When buying a seed-starting medium, make sure it has been sterilized! This should be clearly indicated on the packaging. After it has been thoroughly moistened, the medium can be placed in flats, peat pots, Dixie cups, egg cartons, etc. The size of the container will depend on what type of plant you're growing, and often experience is the best gauge.

If the dreaded damping off fungus does strike your starts, you'll know: all your young seedlings suddenly and mysteriously keel over at the soil line and die. Throw out the infected seedlings, every one. Then make sure any that didn't get infected have plenty of ventilation and not too much water. Don't reuse any infected soil mix, and wash and containers with a weak bleach solution and let them air dry before using them again. In theory, if you use a sterile soil mix, you shouldn't have any problem with damping-off. But if it strikes once takes steps to reduce the chances of getting it again. Give your next seedlings occasional mistings with solutions of kelp or chamomile tea, both of which seem to act as good fungal preventatives. And consider laying a quarter-inch layer of sand or vermiculite on top of your seedling containers to promote drainage at the base of the plants' stems.

Moving Your Seedlings To The Garden

Acclimating - Hardening Off

Six to eight weeks after germination, your seedlings will be vigorous and lush. If nature has cooperated, outdoor weather will be warm, the gardening season begun, and you'll be ready to transplant your starts to their true and final home in your outdoor garden. Tender seedlings grown indoors under constant nursery conditions need to be gradually acclimated to the harsher outdoor environment so they can withstand exposure to direct sun, winds, and changing temperatures. This process is called " hardening off."

When weather is warm both day and night, set seedling containers outdoors in a lightly shaded sheltered spot, gradually increasing time outdoors until seedlings spend a half day, then a full 24 hours outside. Keeping seedlings well-watered and protected from winds, make the transition into direct sun. Begin with just a few hours and increase to a half, then several full days in the sun before transplanting seedlings to their permanent garden position. Make these transitions more slowly if you see signs of stress or wilting.

Transplanting Outdoor

To make the adjustment as mild as possible for your plants, pick a late afternoon or overcast day. Then make sure they are neither too moist or too dry and carefully dig the plants from their flats at you plant them. Try not to handle the root balls as seedlings' fine root hairs are quite fragile. Pick plants up very gently by their stems, trying to keep soil around roots as intact as possible. Keep roots covered and don't expose them to the air any more than necessary. Set each plant in a prepared hole, up to its first true leaves, tamp the dirt firmly around it, then always water it well to get rid of air pockets and assure good root-to-earth contact.

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Article Donated By:
Sam Wilson