Garden myths and opportunities.

A recent conversation with a Master Gardener ended with the question, "so, Don, it’s really too early to plant, isn’t it?" The enduring myth that we shouldn’t plant during the summer got me thinking about other long-standing garden ideas, practices, and products that merit debunking. To use the slogan for a laxative, "gentle correction."

This product emerged in the 1960’s. One brand, we are told, "stimulates the quick formation of new roots hairs and revitalizes the delicate feeder roots that are often damaged in transplanting." Vitamin B-1 is thiamine hydrochloride. Does it really work? Here’s a hint: the manufacturer can’t list it as an ‘active ingredient’ on the label, because they can’t prove that it does anything. After studies indicated B-1 didn’t work as claimed, most manufacturers added low amounts of fertilizer, or chelated trace elements such as iron. Some added plant hormones known to stimulate roots in cuttings, such as naphthalene acetic acid, but these have not been shown to help with transplant shock. The products containing 3 — 5% nitrogen have been shown to be effective in promoting rapid growth of new transplants. Conclusion: ‘starter fertilizers’ do work; Vitamin B doesn’t.

Gypsum, soil penetrants, and sand are often recommended–each for a different reason.

Clay soil absorbs water slowly because the clay particles are tiny. They interlock tightly, with small air spaces, so water can only penetrate as quickly as it can fill those spaces. Compaction of the surface by foot traffic, rainfall, or overhead sprinkling smashes these particles even closer together. If you try to put water on faster than it can penetrate the excess will puddle or run off. Loosening clay soils usually involves breaking the crusted, compacted surface, or amending the soil with products that increase the air spaces. Clay has high cation-exchange capacity, meaning that it readily holds on to and exchanges positive ions.

Gypsum is calcium sulfate, usually sold in powder or granular form. It is a chemical buffer, meaning that it tends to cause the soil pH to move towards neutral from acid or alkaline (we recommend sulfur in this area instead). Advocates say that it "penetrates clay particles and loosens the soil structure," presumably by means of interaction of the calcium and sulfur ions with the clay particles. They caution that it works slowly, requiring annual applications over at least three years.

Soil penetrants are said to work much like detergent, breaking the surface tension, which might slow down water. "Ethoxylated fatty alcohol" is an additive to the Vitamin B product mentioned above. It is hard to imagine that a material sprayed on the surface would make much difference this way.

Neither gypsum nor soil penetrants will have as much effect (if any) on clay as will amending it with larger particles that increase the air spaces. Adding sand is NOT helpful. Although sand particles are larger than clay, they are still just little rocks. In fact, the clay and sand particles interlock to form a structure similar to concrete! But mixing in large amounts of organic material will make a big difference. Composted leaves or manure, or shavings (not fresh), or even fine bark all add air spaces. Even spread out on the surface, these will filter in to the soil by means of weather or worms, continuing to naturally amend the soil as they break down. Organic materials improve the soil’s ability to store and release water and nutrients as well as enhancing penetration.

Compaction of the surface of your lawn’s soil frequently leads to runoff. Here you can break the surface of the soil with a mechanical aerator, and then rake in organic material. In small areas the aeration can be done with a step-on device, while machines for larger lawns can be rented locally. It’s important that the device pulls a plug of soil out, rather than just punching a hole. The popular notion of "aerating" with golf shoes is not effective.

Most plants transplant best–i.e., make the most rapid root growth–when their roots are spread or trimmed to prevent circling, they are planted into warm soil which has been loosened, and they are watered carefully for the next few weeks. Those three factors--root preparation, digging a proper planting hole, and soil moisture–are what determine successful planting, not the calendar! Trees and shrubs planted with care can make considerable growth during the summer. Don’t plant on a very hot day (upper 90’s to 100+)--if you’re not comfortable out there, the plant probably isn’t either. But don’t fret; our delta breeze always comes back.

Temperatures best for transplanting are 55 — 90 degrees F. Our average high temperature in the summer here is about 91F. Brief periods above 90 are not going to harm a new transplant as long as it is properly watered. Check the water daily, but a thorough soaking every 3 — 4 days is more likely to be needed. Don’t rely on a sprinkler system during the early stages, as we fluctuate from the 80’s to the low 100’s every week in the summer, so water needs vary. A windy day is more stressful than a hot, still day.

A common cause of failure in summer planting is from soil fungus attacking plants that are stressed, most often by watering too often. It’s actually better to let the plants go a little dry than to keep them soggy, to keep fungus at bay. Low shrubs with soft wood, such as lavenders and rosemary, and native plants are particularly prone to these diseases–hence the higher failure rate planting these in the summer. Since the fungi involved are heat lovers, waiting until night temperatures are below 55F will reduce losses of these types of plants. But it is primarily a water management problem.

Fall is especially good for planting because nearly every day is in the ideal temperature range. The soil is perfectly workable until we’ve had a couple of inches of rain (that’s usually early November, for those of you new to this climate!). The soil is warm and the days are sunny, so roots make rapid growth–giving them a good head start for the spring–but the nights are cool enough to make the watering easier.

Fall is a great time for lots of garden activities. It’s the best time to plant grass seed, as germination is very rapid. Perennials are divided in the fall if you want to increase or share your plantings. Vegetable gardeners are planting broccoli, cauliflower, cabbage, peas, lettuce, and greens, and onions and garlic can go in anytime through December. There are flowers that love the cooler weather as well–pansies, violas, snapdragons, stock, Calendulas, primroses, Cyclamen, and more.

Have you planted your sweet peas yet?

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