Garden pleasures are not confined to spectacular floral displays.

The sight of a praying mantis, for instance, is just plain riveting. What a magnificent creature to behold!  It is so much larger than any other garden insect and, with its well-defined triangular head, has this ET (extra-terrestrial) aspect to it, as though it descended from another galaxy.  You cannot cease to wonder in amazement at this special visitor.

And yet, not content to simply gaze at this unorthodox insect, you will probably begin taking meticulous mental notes of the circumstances that have brought this beneficial predatory orthopod — a relative of grasshoppers, katydids, and crickets — into your garden.

First of all, there is the plant itself in which your praying mantis resides.  More likely than not, this plant has lots of interior growth within which the insect finds shelter.  There are probably plenty of other insects around as well.  Mantises require live insects for food but their diet is diverse, consisting of flies, crickets, moths, caterpillars, cockroaches, and any of the so-called true bugs.  Numbered among the hundreds of types of true bugs, you will find the “big five” of garden pests.  The big five all do damage the same way, by sucking sap from leaves, stems, and fruit.  These five pests are scale, white fly, aphid, thrips, and mealybug, the first letter of each conveniently found in SWATM, a handy acronym by which to remember them.  You can order praying mantis egg sacs from a wide selection of Internet vendors, including planetnatural.com, which earns mostly five star reviews.  After placing the eggs sacs in your plants, refrain from chemical spraying which will invariably decimate your newly hatched mantids.

Moving on to another intriguing garden guest, the other day I saw, or should more accurately say uncovered, a millipede.  Millipedes and centipedes do not have the hard cuticles you find on insects and thus they reside under moist logs or garden debris to protect themselves from drying out.  Millipedes and centipedes are not insects but instead come from an earlier animal group that goes back to the time of the dinosaurs.  The fossil record reveals millipedes that were more than six feet long once upon a time, while today’s millipedes seldom exceed one foot in length, and are typically less than a third that size.  While millipedes are nearly always vegetarian and are content to eat rotting plant material, centipedes are carnivorous and may administer a painful bite to humans, although it is seldom, except in the case of small children, dangerous.  Incidentally, while millipede means a thousand legs, no millipedes today have near that many legs, while centipedes (meaning a hundred legs) may have between 30 to over 300 legs.  How do you tell them apart?  Millipedes have two pairs of legs per body segment, while centipedes have one pair per segment.  Centipedes, in line with their predatory nature, also move much faster than millipedes.

I have a very small 3 year old lemon tree that doesn’t want to grow. Just a month ago it produced only 1 very juicy lemon. But it keeps losing its flowers. Please help me understand how to solve the problem.

Also, I bought some gypsum to improve the soil around the tree and wanted to know how to apply it.

Nancy Haki, West Los Angeles

Well, if you had 50 flowers on your lemon tree and only one turned into a fruit you are doing just fine, above average in fact.  Even when you are giving your lemon tree — or any citrus tree for that matter — everything it could possibly need in terms of good soil, steady moisture supply, fertilization, and mulch from trunk to drip line, 98% of its flowers will fall off before they are pollinated and can produce a fruit. In commercial orchards, when just 2% of blossoms turn into fruit, it is considered a highly successful yield.

Flowers fall from trees prior to pollination and fruit set for one principle reason: a weak abscission layer between flower and stem.  The abscission layer is a layer of cells that grows between the base of a flower and the stem to which it is attached.  If this layer of cells is weak, the flower will fall off before or soon after pollination.  For example, a spring freeze will damage the cells in the abscission layer and result in flower drop.  Inadequate fertilization will also cause flower drop since the tree “knows” that it is deficient in minerals so why even “try” to grow fruit that will not reach maturity for lack of mineral sustenance?  Lack of water at bloom time will similarly weaken the abscission layer but too much water can be damaging too.

As if citrus does not have enough problems hanging on to its flowers, there is also a problem, on occasion, of hanging on to its fruit.  “June drop” refers to premature fruit drop, beginning in May and extending through June, and is not exclusive to citrus, but includes nearly every fruit bearing tree.  In deciduous fruit trees — peaches, plums, apricots — the cause may simply be insufficient resources to ripen so many fruit.  With citrus, the cause is more often elevated temperatures and low humidity.  When such conditions are recognized, more water than usual should be applied to your trees.  While June drop in deciduous trees refers to dropping of diminutive fruit, June drop in citrus can cause fruit as large as golf balls to fall prematurely.

Although lemon trees are generally consistent bearers, and may have some fruit on the tree at almost any time, certain mandarin (tangerine) cultivars, as well as orange and grapefruit trees, are subject to alternate bearing.  Alternate bearing refers to trees that fruit heavily one year and lightly or not at all the next.  Many deciduous fruit and nut trees are subject to this phenomenon, from plums to pistachios.  While the phenomenon is rather mysterious, there is speculation that, with some trees, the resources required to bring a large crop to maturity depletes those resources to the point that the following year’s crop is sparse to non-existent.

Ms. Haki also asked about the proper way to apply gypsum.  Gypsum or calcium sulfate is a powdery white mineral and a dust mask should be worn when handling it.  It needs to be worked into the ground for best effect.  If your soil is hard, you will literally feel the soil soften in your hands as gypsum is mixed in with it.  Gypsum also lowers soil pH, as sulfuric acid is released when gypsum makes contact with water, which is highly desirable in Southern California since our soil pH is usually on the alkaline side.  Nearly all plants, including many California natives, prefer a slightly acid soil pH.  Some veteran gardeners dust gypsum around their plants every three months and then work it gently into the soil.

Tip of the Week:  Grace Hampton, an assiduous gardener in Burbank, noting my mention of Amaranthus in a previous column, drew my attention to an Amaranthus caudatus cultivar known as ‘Tower Red’ whose inflorescences resemble thick, woolly crimson cattails.  I highly recommend this and other Amaranthus cultivars since they are stunning plants whose seeds germinate reliably in place.  Let your Amaranthus flowers go to seed and you will have a fresh crop of them year after year.