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Extension Spotlight: When is Planting Season in Western Oregon?

March 5, 2017 GMT

That depends on what we are planting. For bare root trees and shrubs, you should plant them between January and March to give them the best chance of developing a sufficient root system to deal with the heat of summer.

If the trees or shrubs you buy are potted and have a good root system, you should still plant them no later than early April to give them time to get established before the high moisture demands of June.

When the weather pattern is as wet as the winter of 2017, it is important to know when you dig a new planting hole in your yard for a tree or shrub; don’t compact the bottom or sides of the hole. Glazing the sides of the planting hole can turn your hole into a pot.

If the sides of the hole become compacted, the hole can fill up with water from rainfall and drown your plant. If your tree or shrubs don’t drown during winter, the roots of the plant will be restricted from growing out into the soil, making it difficult for the plant to take up enough water in summer.

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For a new lawn, there are two preferred planting seasons. The best season for seeding a new lawn is in late August into early September. In late summer, the soil is still warm to help germinate seed, but the day length is receding, making it easier to keep the soil moist with frequent light irrigation.

The second best time to seed turf grass is in April, but following a long wet winter, the ground can be too wet to prepare well. If you wait too long into May to seed, the young grass plants may not have a very strong root system before the heat of summer arrives. Using sod to establish a new lawn is often the best choice for our region in spring.

The cool season crops planted in a vegetable garden like garlic, onions, peas, spinach, broccoli, cauliflower, cabbage, lettuce, kale, collards and leeks are quite frost tolerant and can be planted in late February or March, whenever the soil is dry enough to work.

If the soil is 50 degrees or warmer, any of the cool season crop seed will germinate and establish. If you use raised beds for planting, they stay about 3 to 5 degrees warmer than the ground, helping plants grow more actively through winter and early spring. Starting cool season crops from seed in a greenhouse or in your home and later transplanting to your garden or raised bed is often a good idea when winter is wetter or colder than normal.

When planting warm season crops in a vegetable garden, wait until the soil temperature is at or above 60 degrees. It is also important to know what the last expected spring frost date is for your area. Around Roseburg, the average last frost date over the relatively warm past 10 years is April 15. The average last frost date over the past 30 years is May 9.

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If you think about the current wet season we are having, I would encourage you to be a patient planter with your warm season crops. You may want to test my advice by planting a tomato in your garden in early May, and planting another in your garden in late May. Often, the late planted tomato will look as good as or better than the early planted tomato by July 1.

The U.S. Geologic Service National Phenology Network recently released several maps showing late winter has already turned to spring in much of the Southern U.S. from California to Washington D.C. The warm swath across the south is about 22 days earlier than normal.

The researchers base their maps on nationwide observation of lilacs and honeysuckle, two spring flowering plants known to be very temperature sensitive. These two species in our area of Douglas County are still dormant.

The normal bloom time for these plants in our area is in late April, so it is hard to tell how early spring may arrive here. So far, daffodils and Pieris japonica shrubs are beginning to bloom at the normal time, so I think our planting season will be quite close to our normal for all crops if we dry out for a few weeks.