February is the month when buds fatten and new underground growth accelerates. It is an ideal time to plant, move, prune, or divide permanent plants before leaf growth starts. It is a great time to weed, spade, or till the soil in preparation for later planting of vegetables and flowers.
NEW CLIMATE ZONE MAP
The US Department of Agriculture has released an updated climate zone map for the United States. This revised map was developed with the assistance of Oregon State University. For the first time, the new map offers a Geographic Information System (GIS) based interactive format which makes it internet friendly. It has a “find your zone by ZIP code” function. The new map can be accessed at planthardiness.ars.usda.gov.
Plant hardiness zones are based upon the average annual extreme minimum temperature at a specific location. They do not reflect the coldest it has ever been or ever will be at a specific location, but simply the average lowest winter temperature. Low temperature during the winter is a crucial factor in the survival of plants at specific locations.
The map includes 13 zones. Each zone is a 10 degree Fahrenheit band, further divided in 5 degree zones a and b. Zones in western Washington and Oregon range from 7a (0 to 5 degrees F.) to 9b (25 to 30 degrees F.). Compared to the 1990 map, zone boundaries in the new map have shifted in many areas. The new map is generally one 5 degree half zone warmer than the previous map through most of the United States. This is the result of using temperature data from a longer and more recent time period. The new map uses data measured at weather stations during the 30 year period1976-2005. Does this reflect a gradual warming in our climate?
Many books and plant tags list the USDA plant hardiness zone rating for specific plants. However, the Sunset Western Garden book has its own set of hardiness zones which are completely different from the USDA zones. If you use the Sunset book in selecting plants, be sure to use their climate zone maps. For example, Vancouver and Portland are in USDA zone 8b (15 to 20 degrees F.). The Sunset zone for Vancouver and Portland is zone 6. Zone 8 in the Sunset Western Garden Book is for the Central Valley of California.
COLD HARDY FLOWERS AND VEGETABLES
Cold hardy annual flowers such as pansies and primroses can be planted now for early spring color. This is an excellent time to plant sweet peas from seed, although they can also be planted later. Cold hardy vegetables such as asparagus, rhubarb, peas, lettuce, spinach, and various root vegetables can be planted early. Lettuce and spinach seed will sprout when soil temperature is as low as 40 degrees, and others mentioned at 45 degrees. Cabbage family plants and seeds such as broccoli, cauliflower and kohlrabi can be planted as early as late February. You can check soil temperature with any bulb thermometer by sticking the bulb into the soil an inch or so. If you till or spade your vegetable garden in the fall, it will warm and dry faster so you can plant earlier. Just about any perennial flower can be planted now. Bulbs such as Gladiolus, Lily, and Ranunculus can be planted now. Wait until the soil warms to plant Dahlias, Begonias and other tender bulbs.
Excellent Northwest seed sources are www.nicholsgardennursery.com and www.territorialseed.com. Both companies also have catalogs. You can request one from their web sites.
FRUIT TREE PRUNING
Established fruit trees require yearly pruning for best health and maximum fruit production. Regular pruning will also help keep most of the fruit bearing branches within easy reach for harvesting.
The main pruning job on established fruit trees is to thin out some of the extra branches so that more light can reach those which remain. This also reduces the number of fruits somewhat, resulting in larger fruit with better color. Normally, 1/2 of the smallest branches are removed (thinned) back to their origin. Whenever two branches grow into each other or cross, one should be removed.
All of the branches which grow toward the center of the tree should be removed. The center of the tree should have few small branches except spurs. Spurs are the short, twiggy branches where flowers and fruit are produced on apple, pear, apricot, plum and cherry trees. This allows more light for the ripening fruit on the lower branches. The outward or horizontal branches should be favored over the upright, vertical branches because they will bear fruit sooner and more abundantly. Branches which bend downward are usually removed (thinned) or shortened (headed). This allows light into the inner parts of the tree.
Many times a number of new, vigorous vertical branches (called suckers or water sprouts) grow from the trunk or main branches after spring pruning. These are best removed by breaking them off while they are still small and flexible about the end of May or June. Extra vigorous side and top branches can also be shortened at the same time. Large branches which grow straight up should also be removed.
TRAINING YOUNG TREES AND SHRUBS
Most homeowners assume that trees and shrubs do not need any pruning until several years after they are planted. However, a few selective pruning cuts on plants that have been planted only a year or two can greatly reduce problems in later years. For example, most trees are strongest and healthiest if they have only one trunk or central leader. Upright branches in the upper part of the tree have weak which have narrow branch angles are subject to later breakage and damage when the tree gets older. Branches with crotch angles less than 30 degrees should be shortened or removed. Shortening or removing branches which are about to grow past the main central trunk will restore central leader dominance. Begin shortening extra long branches of shrubs while they are small. Don’t wait until they have grown past walkways and windows before pruning. I am available for free consultation to help you determine which young shrubs and trees may need some early training.
IMPROVE SOIL BEFORE YOU PLANT
The best time to improve your soil is before you plant. Permanent plants can always have mulch added to the top of the soil. However, when you move plants or plant new seeds or plants, be sure to add some organic material to the soil before planting. I like to spade or till 2 or 3 inches of compost or bark dust into vegetable and annual flower beds every year. When planting several shrubs in a group, I spread organic material over the entire area and mix it with the soil before digging holes for transplanting. I like to spade several inches of bark dust into an area at least 6 feet in diameter whenever I plant trees. I also spread lime on the soil and incorporate it with the organic material for all plants except acid lovers like azaleas and blue berries. I always ask or check in garden books or on line to find out if any new plant is an acid lover.