Propagating House Plants

Propagating House Plants: This easy tutorial for growing plants from seed is all you need for expanding your house plant collection.

Growing from seed can be fun and extremely rewarding.

One of the ways of getting a supply of plants for the house is to start them from seed. With a number of varieties, great types of plants can be grown by this method. Most of the annuals, and many of the biennials and perennials, are best reproduced in this way.

As simple as propagating house plants from seed may seem, there are a lot of things which need to be thought of.

We have to give them:

  • A Proper Environment
  • Soil
  • Temperature
  • Covering
  • Moisture

When they get above the soil, they need careful attention until lifted and grown as individual plants.

Naturally, the number of plants you'll want to grow for the house isn't large, and for that reason beginners often try starting their seeds in pots. But a pot's not a good thing to try to start plants in: the amount of earth is too small and dries out quickly. Seed trays and pans oftentimes are better, but even they must be watched very carefully.

A store bought seed starting tray can be used or one can be made for propagating house plants. A wooden box with holes drilled in the bottom for drainage could be used, for example. I've even heard of people using cigar boxes!!


Where most beginners fail in attempting to start seeds is not taking the trouble to prepare a proper soil. They are willing to take any amount of trouble with watering and heat and all that, but they won't get a suitable soil. The soil for the seed box or tray needs to be very porous and very light... especially for such small seeds as most flowers have.

The easiest trick here is to buy potting mix made for starting seeds. However, when propagating house plants, I've always used normal miracle grow potting mix. Every year I have great results. Anything left over, I just use for my outdoor containers!!

Mixing Your Own Soil

Such a soil may be mixed up from rotted sod (or garden loam), leaf-mould and sharp sand, used in equal proportions. If the loam used is on clay side, it may take even a larger proportion of sand. The resulting mixture should be extremely fine and crumbling, and feel almost "light as a feather" in the hand. If the sod and mould have not already been screened, rub the compost through a sieve of not more than a quarter-inch mesh. This screening will also help to incorporate the several ingredients evenly and thoroughly.

Filling The Seed Flat

If using your own seed box (that has great drainage,) fill the box to within about a quarter of an inch from the top, and pack the soil into the corners and along sides and ends. The box should not be filled to the top, because in subsequent waterings there would be no space to hold the water which would run off over the sides instead of soaking down into the soil.


When propagating house plants, the usual way is to fill the boxes or flats and sow the seed, and then water the box on the surface. But a better way is this: When filling the seed flat, set it in some place where it may be watered freely, such as on the garage or porch floor. After putting in the first layer of soil mix, give it a thorough soaking and then put in about two-thirds of the rest of the soil needed and give that a thorough watering as well.

The rest of the soil is then put in and made level, the seeds sown, and no more watering is given, unless it's just enough to moisten the surface and hold the soil in place, if dry. The same result can be obtained by filling and sowing the box or seed flat in the usual way, and then placing it in some place (such as the kitchen sink) in about an inch of water, and leaving it until moisture, not water, shows upon the surface.

Either of these ways when propagating house plants is much better than the method of trying to soak the soil through from the surface after planting, where it's next to impossible to wet the soil all the way through without washing out some of the small seeds.

House Plants From Seed

Photo Credit: Tico

Sowing Seeds

The next step in propagating house plants and after filling the flat as directed, is to make the soil perfectly smooth and level with a small flat piece of board, or a paint stirring stick, etc. Don't pack it down hard...just make it firm. Then mark off straight narrow lines, one to two inches apart, according to the size of the seed to be sown.

The instructions usually given are to cover flower seeds with three to five times their own thickness. But with small house plant seeds like Petunias, you will probably save time by simply trying to cover them just as lightly as possible. I mark off my seed rows with the point of a lead pencil, then sow the seed thinly, and as evenly as possible. A great way of doing this is by shaking it gently out of a corner of the seed envelope by tapping the packet lightly with the pencil.

The next step is to press each row down with the edge of something about an 1/8" thick. This is another good use of a paint stirring stick. Next, scatter over the sown seeds some soil, as thinly as possible, (basically you are covering the seeds just enough for them to disappear from your sight.) And then press the surface flat with a small piece of board or something flat. A very light moistening with a plant mister, and that's it!!!


The temperature required to start propagating house plants will be about the same as that which it needs when grown as an adult plant. Germination will be stronger and quicker, however, if ten to fifteen degrees more, especially at night, can be given. If this can be supplied to the seed box as bottom heat, they'll germinate even better.

Until germination actually takes place, there's little danger of getting the soil too warm, as it heats through from the bottom very slowly. But as soon as the seeds push through they must be given all the light possible and back to the normal temperature as stated above.

If the seed flats or pans are prepared by the method suggested above, they probably won't need any more watering, until the seeds are up. The need for more watering, in any case, will be shown by the soil's drying out on the surface.

Retaining Moisture

In propagating house plants and in the case of small seeds, such as most flower seeds are, the moisture in the soil will be retained much longer by keeping the box covered with a plastic dome which most store bought versions will come with. If you don't have one, a piece of plastic wrap from the kitchen works real well. If the box is going to be kept in bright sunlight, shade the plastic covering with a piece of paper, etc. until the seedlings are up, which will be in a day or so with some seed, but weeks with others.

From the time the little plants come up, the boxes should never be allowed to dry out. If they are being grown in winter or early spring, while the days are still short and the sun low, they will require very little water, and it should be applied only on bright mornings. In fall and late spring, especially the fall, they will require more, and if the boxes dry out quickly, you should apply it toward evening.

In either case, don't water until the soil is beginning to dry on the surface, and then water thoroughly, or until the soil won't absorb anymore. If you have the ability to do it, allowing the seed trays to soak up the water from underneath is by far the best route to go. Pour in an inch or so of water and let them soak up what they need, or until the surface of the soil becomes moist. This does the job more evenly and thoroughly than it can be done from the surface, and is also a safeguard against damping off.

Damping Off??

It's a disease of seedlings which is likely to kill your whole sowing in one day. It's a fungus that causes decaying of the stem just at or below the soil. When propagating house plants, often seedlings will become extremely thin at the soil surface and fall over and die when damping off has occurred.

Light Requirements For Propagating House Plants

From the time the seedlings come up, they should be given around 16 hours of light, and all the air possible while maintaining the required temperature. An oscillating fan comes in handy for air circulation. The air moving across the seedlings will actually strengthen their stems!!

The secret of propagating house plants until they are ready for their first repoting, isn't so much in the amount of care given, but more its regularity. Tend to them every will take only a few minutes of time. When the second true leaf appears they will be ready for their first repoting which is covered here.

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