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Dirty Fingernails: Raised beds can make gardening easier

Dirty Fingernails: Raised beds can make gardening easier

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Raised garden beds

Because a raised bed is essentially a huge container, it should be filled with free-draining mix. Otherwise, the soil in the bed will soon become compacted, and roots will suffer from lack of air.

Q: Because it is getting harder for me to bend over, I am going to do all my gardening this year in raised beds. Should I put gravel in the bottom of the beds for drainage? What kind of soil mix should I put in the beds?

A: A gravel base for garden soil sounds like the perfect way to ensure drainage, but it is not. Because of the way that water naturally drains, it does not drain faster when it reaches the soil/gravel boundary. Instead the water stops draining and pools there, creating what is called a “perched water table.”

If you partly filled your beds with gravel, you would guarantee that the bottom of the soil stayed soaking wet. That is not what you want. Because roots know that they cannot live in saturated soil, they stop growing downward when they reach the wet soil, just above the gravel. Using only soil gives them more room to grow.

Twenty years ago we could still find articles that said to put pebbles in the bottom of flower pots to improve the drainage. Now every garden writer (or nearly every one) knows that this was incorrect information. A raised bed is like a gigantic pot, and the same drainage rules apply.

As long as your raised beds are not built to table height, simply fill them with the soil mixture you want. You need put nothing in the bottom, unless you are worried about quackgrass or tree roots creeping in from nearby. To prevent that kind of invasion, I suggest a permeable membrane like landscape cloth at the bottom of the bed. It will keep out almost all foreign roots while allowing water to drain.

A raised bed where you plan to garden standing or seated would have deeper soil than plants need. To cut down on both the expense and the weight of soil, you can fill the bottom with any lightweight substance; plastic bottles, aluminum cans, or chunks of Styrofoam all make acceptable filler. Top them with a layer of landscape cloth or other material which will let water drain through but will prevent soil from percolating down into the base. Leave about 12 inches of space for soil in which plants will grow.

Because a raised bed is essentially a huge container, it should be filled with free-draining mix. Otherwise, the soil in the bed will soon become compacted, and roots will suffer from lack of air. As long as you have reasonably decent soil, use it for three quarters of the soil mix, and add commercial potting soil for the fourth quarter. Layer the two kinds of soil alternately, or stir them together a little. You do not need to create a perfectly uniform mix. Plant roots and soil-dwelling creatures will continue the mixing process.

Once a raised bed is established, you need not mix soil components at all. When earthworms have established a population, they will do the job better than a gardener can.

Q: I have a greenhouse. What kinds of seeds can I plant now?

A: If you are going to keep your plants in the greenhouse all summer, you can plant seeds for anything except the real heat lovers like peppers and eggplant. If you will be moving seedlings to the garden as soon as they are large enough, your choices are limited. Plants kept in pots too many weeks never grow as well as those transplanted at the appropriate date. If you can’t stand waiting one more minute, there are a few plants—like tomatoes and perennial flowers—which can be transplanted twice, first to a bigger pot and then to the garden.

If you are going to put vegetables into a cold frame or walls of water, which are like individual cold frames, cabbage family plants can be started. My broccoli and cabbage plants are two inches tall (but not the cauliflower; it is cold sensitive enough that I wait two more weeks for it). I will set out these early garden plants in walls of water about April 1, at the same time that I plant spinach, radish, and broad bean seeds in cold frames.

Wait until the last week of March to sprout lettuce seeds in the greenhouse. As soon as the first green leaves appear, move the seed containers to the cold frame. When lettuce plants have four to six leaves, move them from containers to the ground. Lettuce needs warm temperatures to sprout, but it can tolerate cold as soon as it begins to grow.

Q: Is it true that I need to plant heirloom varieties of flowers to grow ones with any scent?

A: No. There are only a few kinds of flowers where every variety is scented. Stocks would be an example. Many flowers are scented in some varieties but not others. There are some scented alyssum, candytuft, cleome, pansies (often the small ones), petunias, and sweet peas. Many varieties of pinks are fragrant, including modern varieties.

Q: How can I keep my variegated ivy from reverting to plain green?

A: You can cut off any branches with plain leaves. That will solve your problem for a while. It may not solve it permanently.

Variegated leaves are more common in house plants than in garden plants. That is because most house plants originated from shade dwellers under tropical forest trees, where natural variegation is not rare. In cooler parts of the world, variegated leaves almost never appear in the wild.

Variegated leaves appear for a variety of reasons, often because of a natural mutation. The mutations in turn have a variety of causes. Perhaps a chloroplast was lost. Perhaps leaves are albinos, although if too many albino leaves occur on the same plant, it will die. Perhaps the variegation arose because of the amount of light coming through the tree leaves above a ground-dwelling plant. Perhaps the plant learned that variegated leaves were a defense against animals looking for green leaves to eat.

Variegation also can occur in a plant which is a chimera; that is, it actually grows two kinds of tissue. Chimeras occur randomly, but they are inherited in future plant generations.

Variegation can appear as the result of a viral infection. A mutation caused by a virus may be stable, even though most mutations are not. One of the best-known examples of this kind of variegation is the flowering maple house plant called ‘Thompsonii,’ which always has white blotches on its leaves.

A plant grown from a cutting of a variegated plant usually is variegated, but not always. A plant grown from the seeds of a variegated plant may be variegated, green, or albino.

A variegated plant may always be variegated. It may remain variegated if green shoots are always removed. It may revert to plain green even with regular removal of green shoots. It may revert to plain green if it is exposed to temperature changes.

To put it briefly, your question is not answerable.

Molly Hackett
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