1 Fruit: If the leaves of your citrus tree are yellow, it’s a sign they are deficient in nitrogen and magnesium, which they need to manufacture chlorophyll, the pigment that makes leaves green. Chlorophyll is necessary for photosynthesis, the process that takes carbon and oxygen from carbon dioxide and hydrogen from water to make carbohydrate, a plant’s energy source. (In this process, the oxygen in water — given off as waste — is the same oxygen we use to breathe.) In any event, the quickest way to fertilize a tree is through foliar fertilization. Many products are available, and organic formulations are often made from seaweed. Kelp is a type of seaweed, usually brown, that grows in tall stands beneath the surface of the ocean. Kelp may reach over 200 feet in height and is the dominant form of seaweed in ocean waters. Fish emulsion — consisting of fish bones, skin and scales — is another liquid fertilizer that may be applied as a foliar spray, but be aware it produces a foul odor. Finally, liquid bat guano and liquid earthworm castings (guano and castings are euphemisms for excrement) are also utilized for foliar fertilization. If citrus leaves are yellow with green veins, the problem is iron deficiency, which may also be remedied with foliar fertilization.

2Vegetables: Fertilize vegetables with the same foliar sprays mentioned above. However, since most vegetables grow for only a season or two, proper fertilization when planting will obviate the need for fertilization of any kind later on. A combination of naturally occurring and organic materials worked into the soil will result in rapid plant growth and abundant harvests. These materials include phosphate rock or bone meal (which is rich in phosphorus; just make sure it is well mixed into the soil so your dog won’t dig it up); greensand, which is sandstone with glauconite, a mineral loaded with potassium, iron and magnesium; and, for nitrogen, blood meal, hoof and horn meal, cottonseed meal, feather meal and, of course, well-aged compost.

3Herbs: Giant hyssop (Agastache species) finds an admirable place in the perennial flower garden and herb garden alike. “Agastache” means “many spikes” in Greek and refers to the plentiful crop of flower wands borne by this highly drought- and cold-tolerant perennial. It grows equally well anywhere from Palmdale to Pacoima to Palos Verdes. Giant hyssops belong to the mint family, and their leaves can be used for making tea. Giant thread leaf hyssop, or licorice mint (Agastache rupestris), is an especially aromatic and reliable garden performer with silvery foliage accompanied by a proliferation of orange flower spikes.

4Flowers: Carpet geranium (Geranium incanum) is one of my favorite ground covers. It has soft, finely laced leaves and superficial roots. Growing to less than 1 foot in height, Geranium incanum self-sows with abandon but is easily deracinated if you should be bothered by where it travels in your garden. Its flowers possess the five overlapping petals of all true geraniums and, in this case, they are magenta rose in color. Usually, Geranium incanum is given exclusive ownership of a garden bed, but I have also seen it used as an underplanting with white iceberg roses. Geranium incanum will need a moderate amount of water to look its best, although it can survive with a single weekly soaking. It flowers throughout spring and summer.

5Insects: To attract beneficial species that feed on garden pests, plant members of the mint family (mints, sages, rosemary, thyme, oregano, lavender, yerba buena and many other herbs), members of the daisy or sunflower family (coreopsis, cosmos, Shasta and Michelmas daisy, sunflowers, euryops, blanket flower, chrysanthemum, Marguerite daisy), members of the carrot family (parsley, fennel, dill, cilantro, carrot) and the verbena family (verbena, caryopteris, aloysia, lantana). In addition, it is a good idea to leave shallow bowls of water in the garden for your beneficials to drink. Put small stones in the bowls upon which the insects can perch.

— Joshua Siskin