Gardening : Coping With Clay : Soil: With work most gardens can be transformed into ones that drain well yet retain moisture.
The gardener’s slant on Creation is that God made Adam out of clay because he was tired of trying to grow anything in the stuff. Composed of microscopic particles, clay’s tight texture is great for making bricks and pots, but clay soil in the garden prevents water from draining downward. Slow drainage and lack of oxygen needed for healthy roots give clay a reputation as a graveyard for plants, but with some work clay can be turned into rich loam that is both well-drained and water-retentive.
Composting, plain and fancy. Strategies for coping with clay are passed down through the generations. In Canoga Park, Jo Kitz’s soil can be modeled into figurines when it’s wet and becomes nearly rock-hard when dry. Adopting a composting technique her grandmother used in the Willamette Valley, she buries organic waste directly in the garden rather than composting it in piles.
“Actually my first intention was to save water by not running the garbage disposal so much. In the end I saved water and got better soil, too,” she explains. Everything from paper napkins and coffee filters to leaves and meat scraps get buried a shovel’s blade deep so the opossums don’t grub it all out again.
This casual composting has worked well for Kitz, especially around shrubs where she could easily dig without disturbing smaller plants. “When I started it was really hard to sink a shovel in the ground, but the next year the soil in that spot was loamy and soft,” she says with a sigh of relief.
Cathy Ratner, who toils in stiff Palos Verdes Peninsula adobe, admits that she has become obsessed with finding ways to improve her soil. She uses a plastic 12-cubic-foot Soil Saver bin that is supposed to produce compost in four weeks.
It takes longer for her, she says, because she doesn’t speed the process by turning and aerating the compost. Now she wishes she had the Green Magic Tumbler, a barrel mounted on a stand that makes turning the compost a cinch. Both composters are available by mail from Gardener’s Supply Co. in Vermont (802-863-1700).
Choose your weapons wisely. What might seem like a labor-saving device can actually make things worse. Using a rototiller on clay turns over the upper layer of soil but can leave the new layer down more compacted and poorly drained than before.
Cathy Ratner’s favorite tool is an English square-tined garden fork she bought nearly 20 years ago from the Smith & Hawken catalogue. Its strong tines have turned over tons of clay and smashed countless clods in all those years. A normal spading fork with flat tines could be bent out of shape within minutes by that treatment. Smith & Hawken (415-383-6399) offer English garden forks in two handle lengths to accommodate shorter and taller gardeners.
The time to improve clay is when it is half-way between gummy-wet and bone-dry. Once a new bed has been forked, Ratner works in equal layers (at least 3 to 4 inches thick) of gypsite, a form of the mineral gypsum, and composted fir bark. She prefers the latter over redwood compost, peat moss or any planting mix containing sewage sludge.
While a garden built on clay profits from virtually any amount of compost, clay is naturally rich in nutrients and needs very little chemical fertilizer. A heavy dose of fertilizer on poorly drained soil can actually be toxic to many plants, so chemical fertilizers should used in half the recommended amount and at longer intervals.
Gentle persuasion. No matter how much you amend the soil, plants you buy in containers will need some convincing that clay is good to grow in. This is because nursery stock is grown in a loose mix of sand and compost that has a radically different texture from clay or improved loamy soils derived from clay.
This predicament stumps even veteran gardeners. For Ratner it is “a really terrible problem because roots used to growing in potting soil don’t want to grow into the heavier garden soil. Instead they tend to sit and vegetate in their pocket of light soil, which of course dries out faster than the surrounding soil.”
She suggests that when you are about to set a new plant in its hole, it helps to remove excess roots coiled at the bottom and to roughen the sides of the root-ball with your fingernails or a stick. Do the same thing to the sides of the planting hole to make a better interface between the two soil types. You also can gently shake some of the potting soil on the roots of the new plant and, once it’s planted, use the hose to wash crumbled bits of garden soil into the root zone.
It’s also a good idea to pick plants that don’t need too much convincing. The list of adobe-adoring plants is not a very long one but it does include some versatile and popular plants. Shirley Kerins, herb garden curator at the Huntington Botanical Gardens, has found that while some plants never adapt to the garden’s heavy soil no matter how much compost is added, certain others perform admirably. Among the winners are scented geraniums, bamboos and other ornamental grasses, sweet violets, sweet bay, myrtle and India hawthorn.
Cathy Ratner recommends such familiar perennials as Siberian irises, white calla lilies, day lilies and Italian arum. Lesser-known plants that excel in her garden include Yucatan daisy vine (Montanoa schotti) a fast-grower that covers itself with white daisies in winter, and velvet groundsel (Senecio petasitis) , an eight-foot shrub that bears large round clusters of purple buds opening into yellow daisies. Both Ratner and Kerins agree that roses, though they enjoy good drainage, will thrive in heavy soils.
