UNITED STATES—Rain is less abundant and less frequent now that winter has become spring. Humidity is decreasing. Temperatures are increasing. Moisture within both the soil and the air is less abundant than it had been. Irrigation that discontinued as the rainy season began should resume soon. Only supplemental watering compensates for the increasing lack of water.
Warmer and drier weather does more than simply deprive vegetation of natural moisture. It also accelerates new growth of formerly dormant or partially dormant vegetation. Such growth requires more moisture as it becomes less available. Increasing day lengths with intensifying sunlight enhance this need for watering. Although natural, it all seems ironic.
This recent need for watering is progressive. Rain still sometimes interrupts it, but will be less frequent as spring progresses. Rain will be very unlikely after later spring. Humidity will continue to decrease as temperatures continue to increase. Watering frequency and volume must increase accordingly. They might not begin to decrease until after summer.
There are too many variables for a simple formula to prescribe watering rates.
Soil composition and texture also influence the increasing need for watering. Organically rich soils retain moisture more efficiently than sandy soils, for example. Gravely soils that drain well may necessitate frequent watering, even if less copious. Potted plants require frequent watering because they can not disperse roots. Hanging pots require even more.
Furthermore, different types of vegetation need different or specialized types of watering. Fibrous but shallow roots usually need frequent watering, even if they do not need much. Species with deep roots usually need watering less frequently. Some of them need more significant volumes of water than others. Some vegetation prefers only minimal watering.
With all these many variables, there are no simple formulas to determine watering rates. Manual irrigation is easiest to monitor, but is also tedious. Automated irrigation, although less tedious, requires more diligent monitoring. For any particular type of vegetation, soil should not remain too dry for too long. Also, vegetation should not exhibit any symptoms from desiccation.
Highlight: Bridal Wreath Spiraea
Flowering quince and forsythia set a precedent. Bridal wreath spiraea, Spirea prunifolia, somehow became old fashioned too. All three are only beginning to regain popularity. All are deciduous, so defoliate for autumn and remain bare through winter. They then bloom spectacularly on bare stems for late winter or early spring. Foliage develops after bloom.
Bridal wreath spiraea, like forsythia, develops many upright and arching basal stems. Its stems can grow taller than eight feet, although they are typically a bit shorter. Removal of old stems after bloom promotes growth of new stems, which bloom better. Indiscriminate pruning ruins their naturally upwardly flaring form. A slight bit of partial shade is tolerable.
Almost all bridal wreath spiraea are of the cultivar ‘Plena’. Their double flowers are fluffy but tiny, between just a quarter and a half inch wide. The simple species, and the variety ‘simpliciflora‘ with single flowers, are rare. Regardless of floral form, floral color is limited to white. Foliage might develop yellow color for autumn where autumn weather is cooler.
Tony Tomeo can be contacted at tonytomeo.com.
