With Christmas less than three weeks away, priorities are shifting to the holiday timetable. Many people are buying Christmas trees and treating them with fire-retardant over the next few days. First-time homeowners are looking forward to their first Christmas in their new home, and they're planning to display a live tree, then plant it in the garden.

There are homes to decorate and holiday plants to buy. On a less festive note, it's also the season to winterize the lawn mower.

Foremost, there's the cut tree. If you haven't shopped already, buy your tree this weekend. Fir trees (Balsam and Fraser) are the best choice because they absorb copious amounts of water. Next best are the pines (among them Scots and White), and last are spruce (Colorado Blue, Norway and White), which absorb very little fluid. The more fluid the tree takes up, the less likely it is to catch fire.

Tree cutting commences around Halloween, but some trees were cut more recently. Before you buy a tree, test it to make sure it's alive.

After narrowing your selection to a few trees, go to the top on the "bad" side of each tree and try to snap a small branch with your fingers. If the branch snaps, consider the tree dead. If the branch doesn't snap, snap it under force with your fingers, then check the color of the stem of the branch. It should be white or green if the branch is alive.

On the way home, buy your fire-retarding materials: a pint of clear Karo syrup, liquid chlorine bleach, and borax (if the supermarket has it, it will be on the detergent shelf). At the garden shop, buy a small bottle of a surfactant, which reduces the surface tension of water and so guarantees greater absorption of the fireproofing solution.

At home, cut the trunk an inch or so from the bottom. Find a large container that holds more than two gallons of fluid. Add two gallons of hot water to the container, then stir in a pint of Karo syrup, two ounces of liquid chlorine bleach, a half-teaspoon of the borax and two ounces of surfactant. Stand the trunk of the tree in the container in a protected spot so the tree won't topple out. After five days, your tree is fireproofed and will stay that way as long as you keep the trunk in the solution.

If you have other decorating plans, consider buying a second Christmas tree, an imperfect one. Cut off the branches, mash the ends with a hammer and insert the stems into the container along with the healthy tree. Remove the branches a day or two later. No needles will drop if you process your boughs this way, and they will have absorbed enough fluid to keep them healthy for the holidays.

When you move the tree indoors, use the largest tree stand possible, preferably with a capacity of at least two quarts. Mount your tree in the stand, then fill the reservoir with the fire-retardant. To avoid spills, transfer the fluid to a watering can, then use this to keep the tree stand filled. Check the stand at least every other day to verify the fluid level.

A live tree that's treated this way is moist and fragrant -- and the needles won't drop.

Don't be shocked to find the tree absorbs all the fire-retarding solution before New Year's. If it does, mix a new batch. There are commercial products on the market for keeping cut trees alive, but they're no better than plain water.

If you prefer cutting your own tree, be sure to test its branches to verify its health.

Here are two other priorities:

First, holiday shopping for the gardener is a joy because it takes you away from the crowds. The most treasured gift of all is a grow light assembly, complete with fluorescent tubes; most garden shops stock them at prices below $50. The lights will be used for starting flower and vegetable seeds, rooting cuttings and for plant culture 12 months of the year.

Second, it's time to winterize the lawn mower. Here's how: Drain the fuel tank of gasoline, then start the engine and allow it to run until it shuts down for lack of fuel. This prevents gumming of the carburetor ports over the winter, saving you $100.

Remove the cover over the air filter, wash it in soapy water to remove grease and dirt, wring it dry, add a tablespoon of clean engine oil to the filter, distribute the oil with your fingers and then put the air filter back.

Drain the crankcase oil. Look for the drain plug at the base of the engine. On some models, the plug is on the underside of the engine (the mower must be turned on its side to gain access). Drain the dirty oil, replace the plug and fill it with clean SAE 30-weight oil, MS grade. Check the owner's manual for crankcase oil capacity.

Remove the ignition wire leading to the spark plug, then use a ratchet to remove the plug. Get an exact replacement at the auto supply store or the mower shop, gapping to specifications (usually 30 thousandths) in the owner's manual. Add a tablespoon of clean 30-weight oil to the spark plug chamber, then slowly pull the starter cord so the oil flows into and coats the engine cylinder walls. Install the new spark plug, but leave the ignition wire off.

Spray the carburetor linkage with carburetor cleaner to wash away the year's grease and grime. When you're through, the linkage should be spotless. Don't lubricate the linkage afterward (oil collects dirt, ultimately fouling up the linkage).

Clean axle fittings around the wheels with a paintbrush dipped in a heavy-duty detergent. Once they're clean, lubricate them with the paintbrush dipped in automotive-quality lube grease.

Let household-grade oil flow down the throttle cable from the handle to the carburetor linkage. Use enough oil so it flows out the bottom, lubricating the cable so it functions well next year.

Wash down the top of the mower housing with a strong detergent, wipe with a clean cloth, then dampen another cloth with an ounce of clean motor oil and put a film of oil on the housing for protection.

Turn the mower on its left side (right wheels in the air). Use a 2-by-4 piece of lumber to chock the rotary blade in place, then use a socket and ratchet to remove the retaining nuts and washers. Remove the old blade and install a new one. Then put the washers and nuts back.

Use a wire brush to remove dried grass clippings from the bottom. When it's spotless, apply one or two rust-proofing coats to the surface, spacing the coats a few days apart.

Finally, check rubber belts for signs of wear and replace as needed. If the mower has powered wheels, go to the gear assembly, remove the filler screw, add SAE 90 gear oil to the chamber until it's full, then replace the plug. Cover the mower with plastic or a tarp for the winter.

Jack Eden hosts "Over the Garden Fence" Sundays from 10 a.m. to 1 p.m. on WTOP Radio (1500 AM).