Hands-Off Winter Gardening
Longtime residents know that winter gardening in the desert southwest is a dream. Set your watering time clocks for less frequency, fertilize on Labor Day, and take your pruners out in January. Oh sure, there’s loads you can plant in your vegetable garden over the winter, but your landscape needs very little at this time. Those not familiar with gardening in our winter climate may not be used to this hands-off approach and may fall into three common over-management habits: over watering, over pruning and over fertilizing.
Over watering is the most common of all gardening mistakes even in the summertime. Plant wilt and general failure to thrive associated with lack of water are also symptoms of over watering. Diagnosing over or under watering is done by what we call the ‘screwdriver test.’ Use a screwdriver or other similar shaped object and poke a hole in the ground, then check for moisture in the soil. If the soil is moist, your plant is wilting from over watering.
Also common in the winter is over pruning. Pruning every month is overdoing it. Plant growth slows when temperatures fall and the plant doesn’t require the same kind of attention that it did when temperatures were over 100ºF. Shrubs like Texas Sage, Dwarf Oleanders, and Cape Honeysuckle really only need pruning three times a year: right after summer, after the danger of frost has past, and just before the heat of the summer arrives. Plants that are over pruned don’t get a chance to flower and mature.
Another common pruning mistake is pruning off frost damage. We may experience below-freezing temperatures several times throughout the winter, which means that plants may experience frost damage several times. Each time temperatures fall below freezing, a portion of the plant will freeze back from the tip of whatever branch is exposed. If you trim off the damage each time, the branch will be exposed to a new frost and therefore be further damaged. The frost damage from the first frost will protect the inner branches throughout the winter. So, as tempting as it is to cut off the ugly damage, wait until after frost danger has past, usually in early March.
Trees, as a rule, should only receive major pruning when dormant in winter. Tree sap flows much more slowly when the tree is dormant, so if we prune in January they won’t bleed sap. All desert trees and all deciduous trees (that is trees that lose their leaves) should be pruned in January. Even many evergreens can be pruned safely in winter. Prune citrus trees, on the other hand, after the fruit is harvested and before the tree blooms again. Light pruning like shaping, cutting off suckers and thinning before summer storms can be done year-round.
Over fertilization is another bad winter gardening habit. After a fertilizer application, plants will spurt new growth that will be frost tender, especially if you use a fast release fertilizer. And, plants susceptible to frost will suffer the greatest damage during a fertilizer induced growth spurt. Three times a year with a slow-release fertilizer is plenty of fertilizer for most plants. We use the “holiday rule” to remember when to fertilize: Valentine’s Day, Memorial Day and Labor Day. Deciduous trees can be fertilized in winter with a high phosphorus and potassium with medium nitrogen fertilizer.
Winter flowers may also need an extra dose of fertilizer. If you notice that your flowers aren’t thriving, they probably just need a dose of fertilizer–not more water. Use the screwdriver test to be sure. Over-watering winter flowers can cause root rot on pansies and mildew and rust on snapdragons. A plant that looks yellowish may have aphids, stress from over watering or a lack of fertilizer. If there are no bugs and the soil is wet, then it’s safe to say the problem is fertilization. Flower Power is a great balanced boost for winter flowers.