As you’ve probably gathered from my last two seed related posts, you don’t need a greenhouse and misting system to successfully propagate house plants from seed. It is really fairly simple and inexpensive.

A number of popular foliage and flowering house plants are commonly propagated from seed, including the umbrella tree Brassaia, False aralia Dizygotheca, tree philodendron P. Selloum, palms, cacti, succulents, geraniums, begonias, and impatiens.

How to Plant Seeds

Unlike seeds of many temperate woody plants, which require a storage period of moist chilling(stratification) prior to planting, the seeds of tropical plants should be sown as soon as they are mature. House plant seeds may be sown in any container with drainage holes. Use a sterilized medium which is low in soluble salts such as milled sphagnum moss, vermiculite, or a mixture of equal parts sand and peat moss. Bottom heat (between 70 and 75 degrees F) aids the germination of seeds and growth of small seedlings. Soil heating cables and mats are available in several sizes to fit individual needs. Inexpensive models for seed flats are usually preset at 72 degrees F. Larger ones, for greenhouses benches and outdoor hotbeds, may be thermostatically controlled.

Sow seeds sparingly and as evenly as you can. Seedlings that are bunched together will have poor air circulation and are likely to fall victim to damping-off, a fungal disease which attacks the seedling stems at the soil surface. If the seeds are so small that they are dust-like or powdery, sow them on top of a moist medium – do not cover them. If they are larger, the rule of thumb is to cover them to twice their diameter. When working with seeds the size of coleus, impatiens, and gloxinia, simply press them into the surface of the planting medium with the palm of your hand.

Label each container with the variety planted and the date. This is a handy reference when you want to determine how long it takes certain plants to grow from seed to maturity. If you want to experiment with different growing methods, be sure to add other information to the label, such as growing medium used, temperature, mist or bottom watering, or depth of planting.

With nearly all seeds, it is imperative to keep the medium moist, but not soaked. Containers with drainage holes can be soaked in a sink or shallow tray of water. Those without drainage can be moistened by misting the surface with tepid water or carefully adding the needed water with a tablespoon. If you are working with very small seeds, it is a good idea to put a clear glass or plastic cover on the container to maintain the moisture, since they germinate better in high humidity. If too much water is added, leave the cover off until the surface appears to have dried out somewhat.

Care of Seedlings

When seedlings show above the soil, they should be moved to brighter light. The first one or two leaves that sprout from most seeds are cotyledons, which nourish the stem tip and the foliage leaves which follow. Until the foliage leaves appear, do not allow direct sunlight to reach the seedlings for more than a few minutes daily. You can determine the amount of light seedlings need by learning the light requirements of the mature plant. For example, geranium seedlings need more sunlight than rex begonia seedlings. An ideal place for seedlings is 3 or 4 inches below a pair of 40-watt fluorescent tubes.

When seedlings are started in a high-humidity container, it is necessary for them to go through a hardening-off period to become accustomed to the drier conditions of the open air. Leave the container’s cover off for an hour or two each day after the sprouts appear. As the seedlings progress, leave it off all day or night, finally removing it entirely. Be careful not to let the growing medium dry out during this process.

Transplant seedlings before they begin to crowd each other, usually as soon as the first true leaves develop. They can go into small, individual pots or several seedlings can be transplanted into one flat or a large pot to save space. As they grow, the largest ones are transplanted into separate containers. Use your fingers and a flat instrument like a nail file or butter knife to separate and lift tiny seedlings. Handle them by their root balls or leaves; it is very easy and usually fatal to crush the stems. Reset them at approximately the same depth as they have been growing and firm the soil gently around the roots. Water thoroughly from below.

Until the plants are established, keep them in a warm, bright place, but out of direct sunlight. Create a high-humidity environment, if possible – it is especially beneficial to plants at this stage. As soon as seedlings begin active growth, fertilize every two weeks with diluted liquid plant food. If the container does not list a strength recommendation for seedlings, mix the fertilizer at one-third to one-half the rate suggested for house plants.