September and October in western Oregon are generally still very hot with high daytime temperatures often in the 80s, while much of the country experiences its first frost or frost. With the current hot and dry weather, it looks like this fall will be ideal for a fall vegetable garden.
This beautiful fall regional weather condition for the Pacific Northwest (PNW) is caused by the moderating effect of the Pacific Ocean which keeps us warm in the fall and mild in the winter. Understanding this climatic characteristic should inspire you to extend the gardening season into fall or, with a hoop, even into winter.
Learning these nuances of temperature and climate in our coastal region can make you a better gardener by putting you in touch with our seasonal standards.
Western Oregon is a great place to grow fall vegetables that tolerate cool temperatures with short periods of frost. These plants include peas, spinach, lettuce, kale, and carrots.
If your garden is a buried plot and you are just starting to plant seeds, you will need to plant in August when the soil is still warm so that the plants will rise up and establish themselves before the cool nights slow down their growth rate.
There is another group of plants that can also be planted in August and will become established in the fall but grow slowly in late fall and winter. Leeks, onions, garlic, broccoli, Brussels sprouts, and cabbage all tolerate frost and a bit of freezing weather once established after about one to two months in the ground. These plants grow slowly in the fall and winter and become productive as temperatures warm in the spring.
If you have raised beds or a garden plot, you can transplant seedlings into the beds in late August or September, and the plants will mature in the spring. For successful winter gardening, install plastic hoops on your garden or raised beds to keep rain out and provide a few extra degrees of heat to the soil for additional growth.
From a climatic point of view, the most limiting factor for winter gardening in our region is excess rain and not cold temperatures.
In our maritime climate, soil temperature is the real key to when you need to plant your fall garden. With our hot and dry summers, the ground is still very hot in September. However, as the days get shorter as fall approaches and the first rains arrive, the soil temperature drops rapidly, making it harder for seeds to germinate.
This is why it is important to plant cool season crops from seed only in August or early September. Use transplants if possible to get started faster if you wait until mid-September.
To garden more effectively in the fall, use raised beds. Raised beds have better drainage than in-ground gardens, dry faster and stay warm longer in the fall. If you have an inground garden and your site is well-drained, you may be able to grow cool-season crops throughout the winter, but without a greenhouse or a cold frame, be prepared for a few problems.
As you move from your summer garden to a fall garden and prepare the soil, be sure to add additional compost or nutrients to make up for the soil nutrients removed by your summer harvest. If you don’t plan on planting a fall or winter garden, it’s important to add compost and plant a cover crop on your in-ground garden plot in September, when the soil is still. warm and the cover crop can begin to protect itself well. your soil in winter.
The worst thing you can do for your garden plots, whether buried or raised, is to leave the ground bare over the winter. Winter rains can cause heavy compaction of the soil in your garden and leach out a large percentage of the nutrients left in the soil after the gardening season ends.
Steve Renquist is the Horticultural Extension Officer for the Douglas County OSU Extension Service.