Soil and Mulch Preparation for Lilies

Lilies are a hardy plant. Still, they will benefit greatly from good soil selection and preparation, as well as a bit of mulch on top.

Like any plant, lilies get much of what they need to grow from the earth without our assistance. But many gardens have been toiled for years and, like large corn or wheat fields planted year after year, can benefit from modern soil-replenishment methods.

In the case of most lilies, that can be a very simple procedure. A little slow-release fertilizer of 10-20-20 strength and most lilies will do just fine. Put it down just before or shortly after the stalks poke up above ground level. Yes, 'just before' means guessing based on your knowledge of the plant from previous years or an average for that particular species. Gardening always involves trial and error.

Soil protection is equally important, particularly in lower-numbered USDA zones where the ground can get very cold and very hard during winter. That low temperature produces a number of potentially harmful effects.

Like any living thing, excess cold can kill cells. Think of how your skin feels when exposed to winter temperatures, especially if there is moisture on its surface. At a certain point, the cells simply can't continue their normal biochemical reactions. They begin to die. If you've ever had frostbite, you know what that feels like. Plants deal with that better than some mammals by going dormant. But there are still limits to how much they can self-protect.

Beyond harm done from contact cold that conducts heat out from the bulbs, ground movement from lower temperatures can do damage, too. Frost heave is a familiar phenomenon in colder climates and it occurs when moisture in the soil freezes and moves the surrounding earth.

Think of the distorted shapes an ice cube tray filled with water will display. That same hump above the level of the tray is taking place under the ground. As it grows it pushes the surroundings, including the earth containing your bulbs. That can turn them to a poor angle, fracture the outer protective layers, or even crush them.

Fortunately, you can help compensate for those effects.

You can do little about any motion of moisture under the ground or the amount of fall rainfall. But tapering off any water you supply as your lilies naturally decay late in the season will help. Less moisture in the soil in fall means less frost heave in winter.

Even better, you can lay down some mulch over the area around where the new stalks will emerge the following spring. That helps insulate the ground above (just as snow does) and prevent ice from forming directly overhead. Snow insulates, but ice prevents the flow of air into the ground, hindering essential gas exchange.

Mulch is also helpful when temperatures are too high. Lilies love sunshine, lots of it. But excessively high heat can damage the most hardy of species. Keeping the bulbs from receiving it is simple. Lay down a little mulch around the base to provide shade.

Mulch also helps retain moisture during those hot summer months. Excessive watering has killed more lilies than under-watering. But the plants still benefit from moist soil. Mulch helps keep it from drying out, especially if your soil is on the sandy side. While good drainage keeps the soil from becoming sopping, which leads to root rot, balance is best.

Mulch also helps suppress weed growth. Weeds, too, need sunlight and starving them at the surface will tend to slow them down. Regular cultivation of the top inch of soil will help, too.

Proper soil care, including addition of mulch, will help ensure that the conditions for your lilies are just right.

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