After the seeds germinate, the bottom heat should be reduced or removed. The warmer the water temperature, the less dissolved oxygen the water can hold. Remember, it’s not overwatering that kills the plant, it’s lack of oxygen. If the water temperature exceeds 78°F, it can’t hold enough dissolved oxygen and it sets up an environment for anaerobic fungi. Anaerobic fungi grow in stagnant, oxygen-deprived water, and they are the bad guys that cause root rot. After the seeds germinate, try to maintain the water temperature between 68 and 75°F for best results.
Adequate phosphorus is also important for faster root strike and better establishment of the plant. Phosphorus is the energy element. It energizes the rooting process, and extra phosphorus is included in most commercial starter fertilizers. With just a little extra phosphorus, it is possible to see as much as 20% more roots.
If the pH rises above 7.5, all of the metal catalysts start to become unavailable and can slow down new growth. Zinc, for example, activates the enzymes necessary for indole-3-acetic acid (IAA) production—the growth hormone responsible for initiating root production.
It’s also a good idea to cover the propagation tray with a humidity dome and place the tray under full-spectrum lights. The dome will keep the relative humidity in the propagation tray at about 98%—ideal for germinating seeds—and the full-spectrum lights will help keep the seedlings from stretching once they germinate. Seedlings don’t need much light intensity. Two standard fluorescent lamps over a nursery tray are adequate, but many gardeners, including myself, prefer four lamps.
Kelp extracts make a great seed soak for older seeds, as kelp is loaded with natural growth hormones and contains many beneficial trace elements. One of the hormones found in seaweed extracts is called gibberillic acid. In nature, gibberillic acid triggers the release of enzymes in the seeds that begin the germination process. Soaking seeds overnight in seaweed extracts may improve germination rates by up to 30%.
In hydroponic applications, stonewool starter cubes are a good choice for starting seeds. A sheet of stonewool starter cubes fits perfectly in a standard nursery tray, and it has the perfect air- to water-holding capacity. Just make sure you condition the stonewool with pH-adjusted water before planting.
Whenever possible, it’s best to use fresh seeds that have been stored in a cool, dark place. Fresh seeds are loaded with starches and stored nutrients, and typically have a good germination rate when given adequate moisture and warmth. If you have older seeds or seeds that haven’t been stored under ideal conditions, a few extra precautions should be taken.
Seeds contain all of the minerals and nutrients necessary to begin growing, so they can be germinated with water only. Once the first true leaves start to appear, however, they need a starter fertilizer. The first leaves that pop out of the seed are not true leaves; they are the embryonic leaves that are formed inside the seed. The second sets of leaves are the plant’s first true leaves. When they appear, it means the seedling is actively growing and that it is ready for a mild fertilizer.
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Giving your plants a strong head start is an important first step towards achieving success in your indoor garden. If your seedlings are weak and spindly, they may not make it off the propagation bench. Even if seedlings do…