The Seasons of the Garden: Soil Blocks and Vegetable Gardening Tips

article image
Rotate your sweet potato plots to ensure proper nodulation.

Greg and Pat Williams, expert gardeners, share tips and ways to utilize new gardening research.

Our Favorite Method for Growing Seedlings: Soil Blocks

Peat pots, plastic flats, foam cups – we’ve tried most of the traditional systems for starting seedlings. But last year we experimented with soil blocks, and now you won’t find us using any other method! The blocks are easy to make, very inexpensive and they work wonderfully. There are several mail-order sources for the little machines that produce these cubes; a four-blocks-at-a-time model costs under $20 and should last a lifetime. And we’ve had excellent results using commercial potting soil with our block maker instead of the costly mixes that are “specially formulated” for soil blocks.

We have run into one problem, though: Top watering causes erosion damage to the blocks, no matter what medium we use. You can get around this by using misters, but then you have to water quite frequently.

We think bottom watering is the way to go. Put absorbent cloth under the soil blocks and stick one end of the cloth into a container of water. The material will act as a wick, absorbing moisture and bringing it to the bottom of the blocks.

Our particular arrangement (which, admittedly, is difficult to move) consists of two-inch soil blocks on an old cookie sheet. One end of a thin cloth diaper runs under the blocks, while the other end rests in a waterfilled bread pan that sits just below the cookie sheet. No doubt you could easily make a more attractive and portable unit from scrap wood and plastic cookware. The important point is that a diaper — or similar absorbent cloth — works just as well as the expensive capillary matting sold by horticultural supply houses.

When using cloths for bottom watering, make sure they’re wet before you add the soil blocks. And don’t let the water containers go dry! You’ll probably need to add liquid only once every few days — no more daily watering or hourly misting!

Research Briefs for Your Best Garden

No-trench asparagus? Are there better ways to transplant asparagus crowns than the tried-and-true, but truly laborious, deep-trench method? Connecticut investigators have tried three methods: planting one-year-old crowns of Mary Washington asparagus in the usual trenches, directly on the soil surface and covered with 3-inch-high mounds and just below the top of 8-inch-high raised beds. After the first growing season, the crowns in the beds and those in the mounds had a significantly better survival rate than the ones in trenches — and more spears per crown, to boot! Time will tell how long-term yields compare among the three methods.

Blueberries love peat! Adding organic matter to heavy, mineral-laden soil is a “must” for promoting good establishment and growth of newly planted blueberries. But not all sources of organic matter are equal. According to Georgia experimenters, peat is a better soil amendment for blueberries than pine bark and far superior to sawdust. (However, two quarts of peat added to each planting hole worked just as well as four quarts did.) And Mississippi researchers have discovered that water-holding gel products are not beneficial. So use peat with blues for best results.

Stop Damping Off. Damping-off, the destruction of young seedlings by soil organisms, is perhaps most commonly due to Pythium debaryanum and Rhizoctonia solani fungi. Standard recommendations for controlling the problem include using sterile growing media, applying fungicides, improving drainage and ventilation, and even watering with dilute chamomile tea. Botanists in India have announced another preventive (at least for damping-off due to R. solani): Simply add organic matter. Their research shows that adding organic materials at the rate of 1 percent by weight to fungus-infected growing media significantly inhibits damping-off of seedlings. Plant materials with a high carbonto-nitrogen ratio (such as straw) were most effective.

Rotate your sweet potatoes. Plan now to rotate your plots of sweet potatoes. Researchers in Louisiana report that old plant residues reduce growth of future vine cuttings — apparently by preventing proper nodulation.

Don’t plant peas in compacted soil. Garden peas are very sensitive to soil conditions — yields can be greatly reduced if they are grown in compacted soil. Experiments in England suggest that recultivating a compacted seedbed to a depth of 4 inches before planting will restore yields to those matching loose-soil levels.