Of the 300 known varieties of asparagus, asparagus officinalis, the little green spears we all know and love flourishes in temperate to subtropical gardens worldwide down to the south edge of USDA hardiness zone 7 which meanders through North Texas and includes Denton County. Local green thumbs plant asparagus roots — which are perennials — in February and March, but don’t rule out starting that bed in September if you can get your hands on some healthy starts.
Bed preparation is important because asparagus likes plenty of compost in slightly alkaline soil. That’s pH fractionally above 7 in a soil test. Lawn lime or fireplace ash help neutralize acidic soil. Standing water will rot the roots, so pick a sunny spot with good drainage.
Unless you start out with perfect soil, plan to work in a 40-pound bag or garden wagonload of compost for each square foot to be cultivated. That sounds like a lot, but if you care for the soil and the worms, they will care for your asparagus, which can produce for an average of 20 years in the same spot.
Mature underground crowns can reach 24 inches wide, and uncut spears can shoot up to 6- feet tall so plan ahead for plenty of space. If rain is scarce, use the hose to give them a drink now and then. Not much will happen above ground during the winter, but the roots spread out, and stems will peek out from under the mulch blanket in spring sunshine.
The asparagus caveat is that gardeners don’t harvest spears the first 2 years after planting. The initial spears put out fluffy green foliage that captures light to make food for the multiplying root cells. The objective is to grow extensive root systems.
Grandma’s harvest rule of thumb is to CAREFULLY cut spears when they reach 8-feet tall and are no thinner than a pencil. Careless cutting damages adjacent spears which flop over and go tough.
A new plot produces for a couple of weeks, but mature plots can provide edible spears for up to 3 months. After harvest time, let the plants grow until frost kills them, then cut the plot to the ground, and let the roots rest.
Growers suggest 25 plants to feed a family of four, but if your crew can’t get enough, think about expanding to 10 plants per person.
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