A few astute readers asked why there is no phosphorus in the lawn fertilizer they bought this year. Of course, my retort was, "Why are you buying lawn fertilizer this time of year as you can't possibly know if you lawn needs it!?" Still, it is a good question.
You may remember that all fertilizers have three numbers listed on their labels. These "NPK" numbers represent nitrogen, phosphorus and potassium, the major essential elements required for plant growth. The higher the number, the more of the element in the fertilizer. Under some conditions, such as those that prevail in the middle parts of this country, phosphorus from fertilizers and manures runs into waters and causes eutrophication, those massive algae blooms that turn water bodies ugly green and anaerobic.
So, a dozen or so states have recently legislated phosphorus out of lawn foods except when seeding. Scotts, the largest provider of lawn fertilizers, removed it from its most popular brands. Others followed.
This is the short answer. The longer answer involves the fact that the world is reaching peak phosphorus and, some would insist, include some discussion of a conspiracy to kill off organic fertilizers because you can't remove the phosphorus from them as you can from a chemical fertilizer.
The longer answer should include a message to Alaskans that our soils contain ample phosphorus already and under our conditions, phosphorus added to soil gets tied up chemically very quickly. For years, back in the 1960s and '70s, Alaskans were told they absolutely needed to add an 8-32-16 chemical fertilizer to lawns (every three weeks). If you have one of those lawns today, you surely still have excess phosphorus. This fertilizer contains way, way too much phosphorus for any use, including in gardens, in my humble opinion. And chemical phosphorus is expensive, by the way.
Here is the trick. Your lawn does need that middle number element. However, without question, the way it should be getting it is by the action of the arbuscular mycorrhizal fungi that form a symbolic relationship with your grass plants and not by adding massive quantities via fertilizer.
So, no phosphorus in your chemical lawn fert? Here is another reason to go organic. First, commercial organic lawn foods contain way less phosphorus and in a more usable form. And, more important, mycorrhizal fungi only operate effectively in an organic environment.
So, here is the rub: If you have been using chemical fertilizers instead of organic ones, you probably do not have working mycorrhizae. You will need to repair this. There are three ways. First, over-seed your lawn this spring with seed that has been rolled in an endomycorrhizal fungi mix (available commercially). Second, you can apply mycorrhizal fungi after aerating. For a large lawn this will be expensive, so consider a third option, the application of MycoApply, a liquid mycorrhizal mix (http://mycorrhizae.com/mycoapply-products/liquid or look for it locally). You might be able to get a nursery to order some if you can't find it.
In addition, the lack of phosphorus in the fertilizer you use is just one more reason to leave those grass clippings on the ground. They contain, obviously (and if it isn't obvious, you need to read my book, "Teaming With Nutrients"), phosphorus. When they decay, it goes back into the soil food web system.
So, no phosphorus in your lawn fertilizer? Can't find 8-32-16 anymore? It is all good, as long as you have mycorrhizal fungi in your lawn's soil. Just follow my directions and you will get there.
JEFFS ALASKA GARDEN CALENDAR
Vegetable seeds to start in individual containers: A must for gardening with kids! Squash, cucumber, tomatoes
Flower seeds to start in containers: Canary bird vine, silene, arctic poppy, California poppy, sunflower, morning glory, sweet pea, Shirley poppy, nasturtium, marigold, balsam, calendula, clarkia, zinnia, bachelor button, scabiosa, nemesia
Dandelions: Time to apply corn gluten, if that is your thing, to prevent new seeds from germinating. It lasts about six weeks. It is not cheap. It takes several years of applications to really work.
Nurseries: Don't wait. Visit and buy now. You can probably harden off in a week or two.
Seed starting for the late bloomer: Thursday, May 7, 6-7:30 p.m., Selkregg Chalet/Russian Jack Springs Park, $5. A beginner's approach to starting seeds indoors on your windowsill. Starting mixes, easy-to-grow plants, care and hardening off seedlings will be covered. Participants will start a few vegetable or flower seeds to take home. Parents must accompany children. For ages 6 and up. Register online at www.muni.org/Active, by phone at 343-6992 or 343-4217 or in person at Selkregg Chalet.
Container Gardening: Tuesday, May 12, 6-7:30 p.m. Selkregg Chalet/Russian Jack Springs Park. $5 Learn how your balcony or patio can be turned into an urban garden. Have a salad at your doorstep. Learn to transplant seedlings into containers. A drawing will be held at the end of class, the winner will take home an herb basket. Parents must accompany children. For ages 6 and up. Register online at www.muni.org/Active, by phone at 343-6992 or 343-4217 or in person at Selkregg Chalet.