African marigold and sweet alyssum are annuals that self-sow in the garden

Note:  the following was written in 2000.  Some years ago, the marigold planter  was converted to artificial turf.

If you want to learn about the importance of soil in the life of a plant, pay a visit to the gas station at the corner of Moorpark Street and Van Nuys Boulevard in Sherman Oaks.
At the corner of the gas station – perilously close to the sidewalk and street – in a modest-sized planter, more than a thousand marigolds are growing. You will not be overwhelmed by a burst of color, for the plants are still in the seedling stage. Come back in a month for a riotous display of orange and gold.
The seeds from which these marigolds are growing were not sown by any human agent. Last year, marigolds in six-pack plastic containers were planted here. The plants bloomed and bloomed. By late December, flowering had practically ceased, but the faded and dried-up blooms were not snipped off. In time, seeds ripened within the moribund flowers. When the spent marigolds were finally removed from the planter early this year, hundreds of fully developed seeds had already been deposited on the soil below. For a few weeks, the soil looked bare. But then the miracle of germination began and, lo and behold, a carpet of marigold sprouts was soon visible.
If you planted a packet of marigold seeds in your garden, you could probably expect a handful of them to germinate, as long as you had a fairly well-drained soil and scattered the seeds over the surface, dusting a little peat moss or compost over them before watering. If you buried the seeds in the ground, it is quite likely that they would rot prior to germination.
The success of the marigold seeds in the gas station planter may be attributed almost entirely to the soil, a fast-draining sandy loam. Sandy loam contains 50 to 80 percent sand.
Most nurseries carry sandy loam soil, usually marketed as “topsoil,” and sold at a cost of around $2 per cubic-foot bag. If you want to improve the drainage in your soil, adding topsoil will certainly help.
Another use for topsoil is in balcony or patio containers. In a container filled with sandy topsoil mixed with compost, you can grow just about anything. Such a soil mix will be pleasing not only to annual flowers such as marigolds, petunias and snapdragons, but to herbs, vegetables, perennials and even palm trees. Conventional potting mix is not only costly but, being highly composted, readily decomposes – that is, disappears – when used in pots. Topsoil, on the other hand, will remain at or near the same level for years.
Remember, topsoil is somewhat low in organic matter and drains rapidly. It should be mixed liberally with compost both to increase its fertility and to improve its water-holding capacity
After the rains, the crust which has formed on the soil surface may give you a feeling that your soil is dried up underneath. To the contrary, this crust prevents evaporation of water from the soil below and should not be broken. The practice of constant cultivation increases the rate of water loss from the soil and destroys beneficial microorganisms that live near the soil surface. It is much wiser to put a layer of mulch – be it compost, shredded bark or straw – on the soil surface both to preserve moisture and to protect the soil ecosystem.
< Grand geraniums
Marshall Maydeck e-mailed an inquiry about sources for unusual geraniums. One of the country’s most important geranium growers, Grand View Geranium Gardens, is located just south of Los Angeles in Carson and grows more than 500 varieties of Martha Washington, zonal, ivy and scented geraniums. Grand View is a wholesale nursery closed to the public. However, the nursery does have an online catalog at www.gvgeranimus.com. Grand View supplies all the major garden centers in the Valley. If you see a geranium in the catalog that you like, your local garden center should be able to order it for you.