IN THE GARDEN YOU ARE NOT THE BOSS OF THIS ASPARAGUS.

Byline: JOSHUA SISKIN

Q: I have a problem with ornamental asparagus that has invaded my yard.

It came from my next-door neighbor, who planted it in his yard. Can you recommend how I can rid myself of this unwanted invader?

-- Fred Lipman,

Granada Hills

A: The plant you mention sounds like Sprenger's asparagus (Asparagus densiflorus `Sprengeri'), a gift no experienced gardener would accept -- unless it was meant for a half-sunny area with somewhat moist, fast-draining soil where nothing else would grow. This is a persistent ground cover, difficult to eradicate, and made positively nasty by tiny, invisible thorns that belie its apparent softness. Still, one man's weed is another man's treasure. It has long, light green, needle-like shoots, up to 5 feet long, which arch and spill over, justifying itself, perhaps, as a subject for planting in a Grecian urn.

The invasiveness of Sprenger's asparagus is attributable to its tuberous roots and prolific self-seeding. This native of South Africa is a major botanical pest in parts of Florida and Hawaii, where it has invaded the habitats and now threatens the viability of indigenous plants. Dig it up and you will find fleshy nodules that impart remarkable drought tolerance.

Conventional herbicides do not work on Sprenger's asparagus.

Repeated digging with religious zeal is required in order to extirpate every last vestige of its roots. If you do grow this plant ornamentally, it is advisable to cut off its flowers as soon as they appear in order to prevent seed formation.

Asparagus in charge

Having surrendered to its indefatigable force, some gardeners comically allow Sprenger's asparagus to grow up uncontested into low-growing shrubs. The asparagus uses the shrubs' branches to frame its growth, upon which it is balled or boxed into discrete, furry green forms.

Foxtail or Myers' asparagus (Asparagus densiflorus `Myersii') is less sun-tolerant and less aggressive than Sprenger's asparagus.

People seem to love or hate this plant, much the way they love or hate Italian cypress, that tall and skinny conifer. Foxtail asparagus is quite plain about what it does, which is to send up fluffy green tails from an ever expanding, if noninvasive, clump.

If you are a flower-arranging enthusiast, you will probably want to have a few clumps of Asparagus setaceus at the back end of your garden. Sometimes called fern asparagus on account of its wispy mien, this plant is not sold at nurseries but finds its way into most gardens.

Fern asparagus should be isolated from the rest of the garden because of its insidious growth habit. It vines surreptitiously into every plant in its vicinity and then, when you try to pull it out, bloodies your hands with its wicked thorns.

All ornamental asparagus types require continuous maintenance due to continuous yellowing and browning as their cladophylls -- we call them leaves although true leaves on asparagus are not noticed -- age and die. They require fertilization twice a year to hold their truest and best green color.

Tip of the week: If you plant a plot of edible asparagus (it's related to the ornamental types) this fall, you may be able to harvest from it as early as next summer.

Preparation for asparagus planting involves digging a trench 1 foot deep and 1 foot wide. Back-fill the trench with four inches of the original soil mixed with a healthy quantity of aged compost or soil amendment. Now spread a 5-10-10 fertilizer and cover with two inches of compost-enriched soil. Set asparagus crowns (asparagus stem bases plus roots) 18 inches apart, in rows, and cover the crowns with two more inches of soil. As asparagus shoots emerge, put additional soil into the trench. Follow the progress of the shoots with a gradual elevation of the soil level until the trench is filled in completely.