Some seeds require proper light also. Some germinate better in full light while others require darkness to germinate. When a seed is exposed to the proper conditions, water and oxygen are taken in through the seed coat.
The embryo's cells start to enlarge. Then the seed coat breaks open and a root or radicle emerges first, followed by the shoot or plumule that contains the leaves and stem. Many things can cause poor germination. Captan, thimet, and similar chemical fungicides are not on the national list and are not permitted. Please take this seriously.
If your seed is covered in a pink or orange powder, it is probably prohibited. We may not be able to certify your crop if you use seed treated with prohibited materials. The first step is to determine whether an equivalent organically produced variety is available. By equivalent variety, look for comparable growing habits, days to maturity, insect and disease resistance, flavor, and other important qualities.
If a suitable organic equivalent variety is not available, document where you tried to look for organic seed, as that is important for your certification records. Once you have found a source for a specific equivalent organic seed, the next step in determining commercial availability is to see if it is of the appropriate form, quality, and quantity.
Compliance is reviewed in the context of the organic system plan, which is verified during the annual inspection. A pattern of inadequate documentation and lack of good faith effort to obtain organically grown seeds and planting stock may be considered noncompliance and might result in Pennsylvania Certified Organic requiring prior approval regarding commercial availability issues in future planting cycles.
Listed below are a number of sources for organic seed provided by Pennsylvania Certified Organic For a more complete listing including forage, field crop, and cover crop seed and transplants, go to the Pennsylvania Certified Organic website.
Fred C. Gloeckner and Co. Gardens Alive! Garton, R. Sikkema, and E. Kemble, J. Alabama Cooperative Extension, Mackean, D. Maynard, D. Knott's Handbook for Vegetable Growers. Hoboken, N. Miles, A. Pennsylvania Certified Organic. Pennsylvania Heirloom Seed Savers Club. Raven, P. Ray, and S. Biology of Plants. New York: W. Freeman, Seed Technology Educational Programs.
Prepared by S. Let's Stay Connected. By entering your email, you consent to receive communications from Penn State Extension. View our privacy policy. Thank you for your submission! Home Seed and Seedling Biology. Seed and Seedling Biology. In order to grow food with a minimum of external inputs, organic producers need to understand much about the biology of plants and ecological systems.
Photo credit: bigstockphoto. Choosing the Right Seed Before exploring how to best grow your seeds and seedlings, start with the right seed. What Do Seeds Need to Germinate? Seeds Need the Right Environment to Germinate Temperature, moisture, air, and light conditions must be correct for seeds to germinate. Table 1. Soil temperature conditions for vegetable crop germination. Minimum F Optimum Range F Optimum F Maximum F Beet 40 85 85 Cabbage 40 85 Cauliflower 40 80 Celery 40 70 85 Chard 40 85 95 Cucumber 60 95 Eggplant 60 85 95 Lettuce 35 75 85 Melons 60 90 Onion 35 75 95 Parsley 40 75 90 Pepper 60 85 95 Pumpkin 60 90 Spinach 35 70 85 Squash 60 95 Tomato 50 85 95 Soil temperatures should be taken by inserting a soil thermometer inches deep into the soil surface and noting temperature.
Seed Dormancy Some viable seeds might not germinate. Steps of Seed Germination Imbibition. The seed rapidly takes up water and the seed coat swells and softens. Think of a pea seed that you have soaked--the outer seed coat becomes soft and wrinkly with water.
Interim or lag phase. During this phase the seed activates its internal physiology, cells respire, and the seed starts to make proteins and metabolize its stores of food MacKean n. Radicle and root emergence. The cells start to elongate and divide, bringing the root and radicle out of the seed.
Early Seedling Development Dicots Two-seed Leaves The primary root, called the radicle, is the first thing to emerge from the seed.
Monocots One-seed Leaves In monocot seeds, the primary root is protected by a sheath coleorhiza , which pushes its way out of the seed first. Dicots and Monocots After the shoot emerges, the seedling grows slowly while the storage tissue of the seed diminishes. Managing for Optimal Germination and Seedling Development Optimizing Germination We know that seeds need optimal amounts of water, oxygen, temperature, and light to germinate.
Seeds purchased within a year of when they are to be planted rarely fail to germinate. However, seeds are often stored from one year to the next, and if they are stored improperly or for too many years, they can loses vigor and germinate poorly when planted. A simple germination test can show whether or not stored seed is still viable. To test seed for germination, count out a sample of at least twenty-five seeds.
Wrap seeds lightly in a moist paper towel, keep the paper towel moist but not soggy for five to ten days. Unwrap the paper towel and count how many seeds have germinated.
We know that seeds need proper conditions to germinate rapidly. Whether seeds are planted into trays in the greenhouse or directly in the field, the goal is to have all seeds germinate close to the same time and grow at the same rate.
A uniform tray of transplants or a uniform field of seedlings is easier to manage and will lead to a better crop. Uneven germination due to slow growth, differences in soil moisture or temperatures, or planting depth of the seed, can result in seedlings of different sizes. This can especially cause problems when transplanting a tray of seedlings; half are ready to plant in the field, and the other half are too small, with root balls that don't slide easily out of the tray cells.
In the greenhouse, one way to achieve rapid, uniform germination is to use germination mats under the trays. These mats allow you to set the temperature according to seed requirements.
Make sure you maintain optimal temperatures for your crop see Table 1. Providing good air circulation during germination and early seedling growing will help to control diseases in this early stage. We cannot control conditions in the field like we can in the greenhouse, but we can still take steps to make sure that seeds planted directly into the field germinate uniformly.
A fine-textured seed bed provides good growing conditions, ample seed-to-soil contact, and the ability to plant to a uniform depth. Planting when the soil temperatures are near optimum will hasten germination and emergence of the seedlings.
Sometimes in the rush of spring planting, seeds are sown in soils that are too cold. This can result in slow germination, weakened and diseased seedlings, and even plant death. It is much better to delay planting until soils warm up. The optimal temperature for growing seedlings may be different from optimal germination temperatures. Table 2 shows the range of day and night temperatures that are best for growing seedlings in a greenhouse, where temperatures can be controlled.
Cooler temperatures generally slow down growth, and warmer ones speed up seedling growth. All seedlings need ample light to grow. If light levels are low or if seedlings are too crowded as they grow, the stems will stretch as the plants seek more light, resulting in weak, "leggy" transplants.
Consider supplemental lighting if greenhouse light levels are low. The length of time that seedlings need to grow in the greenhouse before they are big enough to transplant into the field varies by crop. Tomato and pepper seedlings may take five to seven weeks to produce, while cucumbers and squash are ready to transplant after three to four weeks in the greenhouse. But all transplants need to be hardened off before going from the greenhouse out to the field, or they will be damaged by the harsher conditions.
To harden off seedlings, gradually expose them to conditions they will have in the field. Plants may show some signs of wilting, but do not let plants wilt excessively. After a day or two, weather permitting, set the trays outside of the greenhouse for five to seven days prior to planting. If it is very hot and sunny, provide some shade for the seedlings for the first day or two.
Plants that are hardened off in this manner will be better able to tolerate transplanting, and continue to grow in the field uninterrupted.
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