Proper Ratios Are Crucial When Fertilizing Lawns

Q: When are the best times to fertilize my lawn?

A: In the Pacific Northwest, lawns do best with several applications of fertilizer per year because we have such a long growing season (assuming, of course, that you are able to water normally throughout the summer). Each year, apply 4 to 6 pounds of actual nitrogen per 1,000 square feet of lawn surface, but divide the application so that about one pound of actual nitrogen goes on each time.

Use a fertilizer with a 3-1-2 ratio; in winter; a timed-release type can be helpful. If you want to apply 4 pounds actual nitrogen per 1,000 square feet per year, divide it into 1 pound applied in November/December, April/May, June/July, and September. To put on 6 pounds per year, the optimum times are November/December, April/May, June, August, September, and October.

Notice the absence of March? Though traditionally people fertilize then, that isn't the best month in the Northwest. And remember that water is vital for all fertilizer applications, be it from rain or hoses and sprinklers.

What is actual nitrogen and how much of your fertilizer do you have to apply to get that 1 pound per application per 1,000 square feet? The fertilizer bag will carry a number series, such as 12-4-8, or 21-7-14. To figure out how many pounds to apply if you want one pound of actual nitrogen, divide 1 by the first number (the nitrogen percentage). For a 12-4-8, 1 divided by 12 is .0833 which rounds off to 8 pounds per application. If you have a 21-7-14, it would be .0475, rounding off to 5 pounds per application.

Q: How can I control blackberries?

A: "Ubiquitous" is the word for blackberries in the Pacific Northwest; the big Himalayan type was introduced from other locales but has settled in like a native. Control is probably a good word; you may not be able to completely eliminate blackberries from the landscape, especially if there are untended stands nearby with shoots and seeds to move into your yard.

No one who's ever approached one of these needs to be told about the thorns; blackberries carry skin-ripping, glove-destroying thorns. Wear heavy leather gloves with cuffs and tightly woven clothing. Or armor if you have any. You can chop back the top growth, drag it away (don't compost it), and grub out the roots with shovel and mattock or pick. Blackberries, for all their vigor, are rather shallow-rooted and a good thorough digging will often reduce the infestation considerably.

Be sure to try this mechanical control (chopping and grubbing) method first.

If you have a hillside swath or a huge area, and choose to use an herbicide, you can use the hormone-type such as Round-up or Blackberry and Brush Killer. Late fall is a good time to treat the plants if the leaves are still green and growing actively. If the plants have died back, there's no point to using one of these herbicides, which need to be carried in live tissues.

Choose an herbicide with a label stating that it will handle blackberries and brushy weeds. Be very careful if there are any cherished landscape plants in the same area; read the label and apply with caution. You may use a watering can or sprayer, if you have only one or two plants. The herbicide must be applied to leaves and translocated back to the roots to do the job, and it has to be applied on a dry day.

A quicker and tidier method is to cut the plant off, leaving about 6 inches of stem above the ground, and immediately paint the cut end with full-strength herbicide. Buy the smallest quantity you can and mix up no more than you need. Wear goggles, unlined rubber gloves, and rubber boots.

Gardening runs Friday in Scene and Sunday in Home/Real Estate. It is prepared by George Pinyuh and Holly Kennell, Washington State University/King County Cooperative Extension agents, Mary Robson, Master Gardener program assistant, and volunteer Master Gardeners.