For an Early Start in your Herb Garden, Germinating Herb Seeds may make sense.
Growing plants from seeds can be a rewarding hobby and allows home gardeners to grow herb varieties that may not be available from herb plant growers. Many garden herbs may also need a jump on the growing season by pre-starting the herb seeds indoors six to eight weeks before the last spring frost in your herb garden.
Germinating herb seeds is not for all gardeners or even the herb plants. Some annual herbs are better planted directly into your herb garden and do not benefit from the time and effort of germinating herb seeds early.
Before you invest the time and expense of starting the herb seeds early, review your stock of herb seeds and determine for sure which of your tender herb seedlings will successfully replant into your herb garden.
Starting Herb Seeds and notes of caution.
Herb Seeds Purity and Trueness to Type - Herb seed packets which contain should not contain seed of other crops or weeds and should be the correct variety. There are some herb seeds for sale that are simply labeled, for example, "Basil" or "Oregano." There are many different sub-species and cultivars of the many different herbs available. Buy only quality seed from a reliable herb seed supplier which is correctly labeled listing the species or sub-species and cultivar of the herb you want to grow.
Use "Oregano" as an example - A quick check of my favorite herb seed supplier shows 14 different species or "varieties" of Oregano easily available. Although, most look very similar when viewing the picture of "Oregano" on the seed packet, the hardiness, taste, and aroma would be a distressing wakeup call for the unsuspecting herb gardener! Look for the Genus and species listed on the seed pack; if not found, just leave it on the shelf.
Herb Seed Packaging - Seeds sold in packages should show the true herb seed name, variety and any chemical seed treatments. Herb seeds stored in laminated foil packets ensure dry storage and are preferable. Paper packets are less desirable and are best kept in tightly closed cans or jars until the herb seeds are started.
Access to the Newest Herb Seed Varieties - Starting Herb Seeds early may give you the benefit of obtaining the newest herb varieties that may not be available from over-the-counter sources. The herb seeds may cost slightly more than some older herb seed varieties. Because of they are "new" they usually have increased vigor, better production and should contain specific disease resistance or other unique cultural characteristics. Each herb gardener must decide whether the added benefit justifies the small additional cost.
Starting Herb Seeds for your Herb Garden
Starting Herb Seeds successfully requires good timing, good herb seed starting medium, light, moisture, temperature and patience!
Depending on the herb seed, plant seeds from four to ten weeks before the last spring frost date. Sowing seeds at the proper time indoors allows them to grow into robust seedlings ready to plant into your herb garden when outdoor weather conditions and temperatures are right.
Most gardeners time their plantings relative to the average date of the last spring frost. A quick phone call to your local Extension Office is a great way to find the historical average date of the last spring frost in your area.
Starting Herb Seeds in the correct seed starting media is critical; the growing medium must be sterile. Do not use plain or any mix containing garden soil!!! Herb Seeds contain the food they need to germinate. A sterile seed starting mix is always preferable. The medium used for starting seed should be loose, well drained and fine-textured. Herb seed starting mixes are widely available and, in my experience, always out perform home mixed seed starting medium.
Vermiculite: When used alone vermiculite provides good seed germination. It is clean, and if not contaminated during handling, will not need sterilization. If another herb seed starting seeding mix is used, vermiculite it is useful for covering seeds since it provides easy emergence for the seedlings and helps to protect the tender herb seedlings against damping-off. From what is available, a fine grade of vermiculite is best for starting herb seeds.
Synthetic soil free mixtures: A combination of finely ground peat moss and vermiculite or peat moss and perlite can be purchased ready-mixed.
Home-mixed Seed Starting Medium: For those like to live dangerously and with extra time on their hands mix: 4 quarts Vermiculite, 4 quarts finely ground Sphagnum peat moss, 1 Tbsp. super phosphate and 2 tsp. pulverized limestone.
I conducted a side-by-side trial between my home-mixed herb seed starting medium similar to the above mix and four random choices of commercial herb seed starting medium. In every test the personally mixed medium was a resounding loser. I have never again bothered to mix my own seed starting medium.
Milled sphagnum peat moss: This is a ground sphagnum moss sometimes used for starting seeds since it appears to have an ability to inhibit the seedling disease "damping off." It should be well moistened before use.
A combination of any of the above: It’s a viable alternative, but then why bother.
The above mixes, have little fertility. Seedlings must be watered with a liquid soluble fertilizer solution soon after they emerge.
Starting Herb Seeds in sterilized pots or seed flats containing a sterile seed starting medium is critical to the health of your growing herb seedlings
Sterilized potting Soil: It guards against plant diseases carried in soil and on containers. Cleanliness and sterilization of pots and containers materials is also important. In addition to killing disease organisms, many weed seeds are also killed by sterilization.
The seed starting mixes may be sterilized directly in the pots or flats in which they are to be used. If you are starting herb seeds in plastic seed flats or plastic pots, first sterilize the seed starting soil in a metal baking dish.
While the soil bakes it may give off a strong odor, so some ventilation may be needed. The length of time necessary for sterilization depends on the amount of soil and its moisture content.
- Cover the seed germination medium with aluminum foil, sealing the edges.
- Poke a hole in the foil and insert a meat or candy thermometer into the soil so that the bulb is about at the center of the seed germination mix.
- Warm the pan in an oven at 200 to 250 degrees F, but not warmer! Warm the soil until the thermometer shows a temperature of 160 to 180 degrees F.
- Remove the metal seed germination container and allow it to cool. Following the sterilization process, move the cooled seed starting medium to plastic seed starting flats or pots.
Do not put plastic seed starting flats or pots in the oven!
After the soil has been sterilized, make sure that containers and tools are also clean and sterile. Clean soil can be easily re-infected by dirty containers and pots. Drop used pots or trays in a weak bleach solution for a few minutes, remove and rinse thoroughly.
Containers and Growing Conditions for germinating seeds
When germinating seeds, containers should be clean, sturdy and fit into the space available for the growing plants. The proper type of seed germination container will help get seedlings off to a good start and will save work when transplanting seedlings.
Plastic trays, fiber trays: Plants that are easy to transplant may be seeded directly in flats or trays for later transplanting into individual pots or wider spacing in flats. Starting seeds in such containers saves space as compared to seeding directly into individual pots. If the space is available, direct seeding in pots may be desirable.
Clay and plastic pots: Both types can be cleaned and reused and provide excellent growth for transplants. They must be removed from the soil ball carefully at planting time. Seeds may also be planted directly into them which will eliminate transplanting your herb seedlings before planting the herb plants into your herb garden.
Peat pots: Peat pots are made from peat or paper waste fibers and may be purchased individually or in blocks. They are porous and provide excellent drainage and air movement, though if seedlings are left in the pots too long they may become soft to handle. The entire pot can be planted in your herb garden with less root disturbance at planting time.
Sterilizing containers: Soak or wash seed germination flats and pots in a 10% solution of chlorine bleach and water. Rinse thoroughly and let them dry before filling with soil.
Temperature: Generally, germinating herb seeds will do better if their soil temperature is kept 70°F or above. Some herb seeds germinate best at 80° to 85°. No other factor will speed up herb seed germination more than a constant warm temperature. Do not depend on a windowsill; it is generally too cool for good germination, particularly at night and the morning. You may want to invest in a bottom-heating seed propagation mat. They are extremely effective in keeping seed germination flats at above 70 degrees F.
- Moisture: Seeds also need to be kept constantly moist in order to germinate. Two key words: constant and moist. Never let the germination media dry out. Water as often as needed, but don't pour water on un-rooted seeds. Using a plastic spray bottle is best. The water should be at least room temperature. It is advisable to allow chlorinated water to stand for a day to allow the chlorine to dissipate.
- Fertilization: Fertilization of your germinating herb seeds is not necessary as herb seeds carry enough of their own food to germinate. Shortly after germination, though, when the herb seedling show two true laves start giving seedlings some nutrients. Any all purpose fertilizers such as Rapid Grow™ or Miracle Gro™ soluble fertilizer will provide what is needed for healthy growth.
- Organic feed: Such as Shepherd's Sea Mix or garden-center fish emulsion, can also be used, if you don’t mind the smell. Feed seedlings once or twice a week by applying fertilizer only at a half strength concentration. As they get bigger with several sets of true leaves, the dose can be increased to full strength, according to the manufacturer's directions.
Planting your Herb Seeds
Fill containers near brim full and completely moisten the soil. Smooth the soil and pack it firm. Place the seeds in rows on the surface of the soil, labeling each herb plant variety as the seeds are sown. Space seeds half-inch apart if the intention is to transplant them to a second grow-out flat later. Plant 1 to 2 inches apart if they are going to be kept in the same flat until garden time. Sift soil mix over the seeds to the required planting depth indicated on the herb seed packet.
Plant herb varieties in each seed flat with similar germination times and planting depth. Consult our herb articles regarding individual herbs for this information or read the back of the herb seed packet. Plant a few more seeds than what is needed. They may not all germinate, and it is best to have extra seedlings.
To conserve moisture cover each flat or pot with plastic wrap or other transparent cover. Using a spray bottle keep the herb plant flats evenly and consistently moist . Water each flat or pot with a mister or spray bottle. Pouring water directly into the flats can wash the germinating medium soil away from the seeds.
Maintain 65-75 degree temperature. Set the trays in a warm spot or preferably on an herb seed germinating heat mat. Some Herbs require higher or lower temperature. Consult particular growing instructions for each of the herb plants.
Watch daily for germination. Containers should be moved to bright light and the plastic domes should be removed as soon as germination is well under way. Different seeds will emerge at various times.
Keep only the very best herb plant seedlings. It is hard for first timers herb growers to discard seedlings nurtured so carefully, but it is a necessary step. Overcrowded seedlings always develop into inferior plants never likely to succeed in the garden. Initiate thinning and spacing herb seedlings as soon as they have a set of "true leaves." Proper thinning can be accomplished by using a small scissors and snipping off the weaker and excess seedlings at soil level.
Water the young herb plants. When the new herb plants are at a few inches tall, let the top half-inch or so of soil actually have a chance to dry out between watering. Check soil moisture daily by putting your index finger into the soil.
Damping-off fungus may attack the young herb plants if they are kept too damp. If so, the young plants suddenly and mysteriously wilt, fall over then die at the soil line. High temperature, poor light or excess moisture stimulate spread of the disease by weakening plants to make them more susceptible. To help protect young seedlings consider bottom watering your seed flats as shown.
At the the first sign of herb seedlings damping off, drench the entire soil mass with a fungicide available at one of our garden suppliers. Immediately discard the infected seedlings by digging out the infected plants and soil. Make sure those that didn't get infected have plenty of ventilation and not too much water. Spread a shallow layer of dry vermiculite around the base of the affected seedlings to help keep the herb stems dry.
With dedication, the right supplies, and a bit of herb gardener's luck, you can germinate herb seeds that will develop into strong, young, herb plants and do your herb garden proud. Again, the key is: good information, quality seed and supplies, a good plan, and that "gardener's luck" we spoke of. With the above, you will find that germinating herb seeds is one of the more rewarding facets of growing herbs in your own herb garden!