In last week’s column, I discussed the need to lower the amounts of nitrogen we feed our plants during a drought. Higher nitrogen percentages (above 5 percent) in commercial fertilizers encourage rapid growth or flushes of new leaves and twigs. Root systems usually will draw up more water to sustain rapid growth, but during the drought conditions we can expect again this year, the extra water simply won’t be available. We saw many annual and perennial plants die as well as massive tip die-back and limb death on trees during the previous four years of severe drought; one means of reducing die-back and plant death is to apply lower nitrogen fertilizers less often.
Here’s a list of revised fertilization guidelines for this drought season:
Fruit and nut trees – Fruit and nut trees require two fertilizations during the productive season. The first should be applied as they come out of dormancy or at bud break in spring; the second is applied after harvest in fall.
A cup or two of high-nitrogen ammonium sulfate (21 percent nitrogen) per feeding per tree is normally recommended. This year try applying the same amount of a lower-percentage, all-purpose fertilizer, say a 6-6-6, or the same low-nitrogen food you should use for your tomatoes, such as a 4-6-2 formulation. Citrus which are fed three times in spring (late February, March and late April) should be fed lower amounts of a high-nitrogen fertilizer or the amount that’s applied of a good quality citrus food can be cut in half.
Roses and other perennial flowering bushes – Roses and other summer-blooming perennials including rudbeckia, coreopsis and hydrangeas are best fed monthly during the bloom season with a half-cup or cup per plant of a higher phosphorus (the middle number), low-nitrogen granular fertilizer. The 4-6-2 formulation mentioned above works well on all flowering plants. Shade plants such as hydrangeas, azaleas and camellias are fed during the summer months with a fertilizer containing extra sulfur. Cut back to a half-cup of a low-nitrogen, higher-sulfur fertilizer once a month for shade plants.
This drought year, stop feeding all plants and trees during the hottest months (July and August) when they are semi-dormant due to extremely high daytime and nighttime temperatures.
You might also experiment with applying compost to your flowering plants instead of fertilizer. My own experimentation last year with applying homemade organic compost made of kitchen waste (approximately 1 percent to 2 percent nitrogen) rather than fertilizer had disappointing results when only a couple of cups per plant were dug in monthly. Weak stems, poor flower production. But when amounts were increased in September and October to four cups monthly per plant, new growth and bud set improved (but so did the weather).
Herbs – Herbs thrive in our arid hot climate and generally need little or no fertilization. The tender-leafed culinary herbs such as basil, tarragon, parsley and coriander are exceptions since their crop, the leaves, are harvested so often. Give tender-leafed herbs a tablespoon or two per plant of an organic higher-nitrogen fertilizer (5 percent to 6 percent) to maintain consistent new leaf production. Pinch back flowering tips as soon as they appear.
Elinor Teague: firstname.lastname@example.org