Master Gardener Presentation Notes > Seed Starting

Seed Starting

By Don Neu

(From our March 2002 Brown Bag Lunch Lectures)

Why start your own seeds?

  • Wider variety in seeds than in plants
  • Cost is much less than for plants
  • Quality plants if you raise them yourself
  • Disease free plants
  • Pesticide free (unless you add it yourself)
  • Extend the growing season
  • Earlier blooming than direct seeding
  • Sense of accomplishment

What do you need to start seed?

* Seeds (fresh are the best) All seeds sold in stores must meet federal germination standards. Make sure you know what you�re planting-some plants need to be started earlier than others. Peppers and tomatoes can be started as early as January, other plants later. Not all seeds are recommended for starting early or inside--just too big/lanky/not suited to indoor growing.

* Seed starting medium, Jiffy 7�s or 9�s, mix your own from differing amounts of peat/coir and vermiculite/perlite. Usually your best and simplest bet if you're just starting out is to buy a mix especially for seed starting. DON'T use regular garden soil--it contains microorganisms that will cause your newly sprouted seedlings to develop a disease called "damping off".

* Flat (or tray) with dividers or other container with a clear lid or could have Saran Wrap put over. There are a myriad of different varieties of these plant starting containers. The ones we used are cheap--under $3. They can be reused over and over again.

* Warm place for germination (not necessarily dark unless so required on the seed packet-ex. delphiniums. Most plant seeds germinate best at soil temps around 75 degrees F. Use a warm radiator, top of a fridge, heat vent, or you can buy heating mats designed especially for starting seeds.

* Warm sunny windowsill (S or W exposure) or fluorescent lights. Use a combination of warm white and a cool white bulb for a full spectrum. (Special grow bulbs can be used, but they tend to be not as efficient as regular bulbs.) Note that the light at the end of the tubes is not as strong as the light in the middle. At home, I use a 4ft shoplite fixture with 2 fluorescent light bulbs.

* Water/spray bottle. Almost any will do. You want something that you can mist your seeds before you cover them with soil and something to water them when they're tiny and fragile after they just sprouted

* Liquid apply fertilizer -Miracle grow, fish emulsion, etc. Since the seed starting mixture doesn't contain any nutrients, you need something to give your plants nutrients to grow from once they've sprouted. Generally a fertilizer with a lot of Phosphorus is what you want (It's the middle number in the usual fertilizer numbers--for example 10-10-10) to stimulate root growth. Typically you want to have more phosphorus than nitrogen (the first number) since plants with too much nitrogen will get really lanky indoors and be more susceptible to pests. The fertilizer I use is something like a 10-30-10, if I remember correctly.

Make sure with your seedlings to dilute the standard mixture by half if not more--since too much will burn them and they are sensitive when small.

* Labels--make sure you label your trays!! Nothing is more frustrating than having 20 flats of mystery seedlings. Besides, even if you know what the seedlings are, you may not be able to tell apart the variety--which can be important later on in the year. Your best bet for labels is to use tape and permanent marker on the trays and plastic window shade laths in the garden with pencil.

* Journal--you'll want to keep a journal so you can compare from year to year--and try different things to improve how you are doing things. As one author puts it, we may be doomed to making mistakes, but we aren't doomed to repeating them!

Starting seeds

* Make sure the container you�re planning to grow seeds in is clean. You can re-use old flats or pots, but wash them out with a bleach and water solution (1:10) to kill any fungus, mold, or insect that might remain behind. Rinse well and let dry.

* Prepare the potting mix according to the package directions. Most mixes contain a considerable amount of peat to keep the medium moist so most likely you will need to mix water to make the medium workable. Use a bucket and mix the soil with the water and put into clean containers.

* Prepare the soil for seed. Using the pencil and a ruler, make a hole in the soil of the depth prescribed by the seed planting directions. For small seeds, sprinkle on top. Take care to note any special directions-some seeds require complete darkness to germinate, others germinate better if frozen first, some should be soaked, others need to have their seed coat scratched.

* Label your containers before you plant!! Insert the seed and spray with a water and fertilizer mixture to make sure the seed itself is wet. Cover with soil. Note-only plant seeds of the same germination time in the same container for best results.

* Cover the container with the clear lid or Saran Wrap to hold in moisture and heat. Place container in the warm place. Often a heat register, inside closet, top of fridge, or radiator will work well. Check every couple days for adequate moisture (usually not a problem if well covered) and for germination.

* When seeds first germinate, they will start with only 2 leaves. At this point, bring the container (Still covered) to a sunny windowsill or put under grow lights. Keep lights close to plants as they grow. The soil must be kept warm or the seedlings will "dampen off". Maintain a good amount of moisture in the container using the sprayer. Don�t spray the plants too hard at first. Don�t over water!! You want the soil to be moist, not sopping.

* Once plants have developed their real leaves, and are reasonably established, you can remove the top from the container. However, protect them from cold drafts and check frequently for moisture. Don�t over water!

* Pinch back the top two leaves of the plants if they get lanky (this is after they have 4+ true leaves) to help the plants become more bushy (tomatoes can be buried so you can let them get lanky). Rotate your pots under the lights and in the window to keep the plants from growing all one direction, and use an oscillating fan on low to help strengthen stems.

* Hardening off-When you're ready to plant out, you need to harden your plants off to real sunlight and outdoor conditions. Setting them outside on a warm afternoon for a couple weeks is your best bet. Don't forget to take them in when it cools off at night! Be sure watch out for hungry rabbits, and wind that can topple containers, injure young stems, or dry out your plants. I like to put mine out in my porch a few weeks before I plant out to acclimate them a little bit and bring them out to get sunshine in the afternoons. Usually a week or so is enough.

* Plant out--after danger of frost is past--usually May 15th around here. If you use peat pots, shred them slightly if the roots haven�t grown through them...otherwise leave them.

* Storing leftover seeds--Leftover seeds are best stored in a tightly sealed jar in the refrigerator or other cool (but not freezing!) place. I keep mine in glass jars in the basement. Don't just store seeds in paper envelopes, etc. Exposure to air will degrade their quality. Note--some seeds just don't store long--delphinium seeds typically only last a year. Yet others can last for ages.

* If you have a lot of interest in starting seeds, check out some books from the library on starting seeds and gardening, ask local gardeners, as well as check the internet for helpful information.

Potential Problems:

* Damping off disease-a soil disease caused by a bacteria that attacks the plant stem at the soil line. Usually caused by not cleaning your pots properly, using regular garden soil to start seeds, a soil that is too cold for your plant type, and too damp of soil. Will kill a whole tray if allowed to spread.

* Mold- if the soil is too cold or damp, mold could grow. Isolate the pot and decrease humidity (uncover) and keep a very steady warm temp and you might just be able to save your seedlings. Note: Most seeds, when left to grow on the soil put out a white fuzzy root that might look like it's covered in mold. But it is only the new root hairs. Generally, when I run into mold, it tends to be a greenish-blue color or grows around the seed in a cottony appearance.

* Over watering--nothing is more efficient at killing plants than too much water or not enough.

* Not enough light-plants get too leggy, yellowish

* Plants get too leggy-pinch off, use a fan.

* Plants get wilty, die off, especially tomatoes--could be a natural gas leak. Tomatoes are particularly sensitive to natural gas so if you have a natural gas stove, keep them as far away as possible and check the stove for leaks.

* Insects pests--some indoor favorites are aphids, spider mites, thrips, mealy bugs, and others. Your seedlings should be fine unless some of your other plants are already infected. Check with a gardening expert for control.




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Last revised on October 23, 2009.