The Pacific Northwest has a very moderate climate, which makes for a good growing season; but the rain and pest pressure can have some looking for relief, while others may just want to extend their season to increase production. Either way a greenhouse could be the answer you are looking for. You will be able to control how much water each of your crops get, have a physical barrier to help manage pests and you will be able to extend your season, or even grow year round. A permaculture greenhouse doesn’t just have to be for the health and benefit of your plants, but for you as well. Having an oxygen-rich environment filled with a beautiful, lush garden can be a welcoming delight on those dark, winter days.
A permaculture greenhouse is about working with nature, which means growing a variety of crops and plants. Flowers, herbs, fruit, vegetables, and leafy greens can all be integrated together to create an ecosystem that will attract beneficial insects and pollinators while feeding you and your family. You may not be able to eat or harvest every plant in your greenhouse, but they should still serve a purpose beyond pure diversity. You can plant different flowers and shrubs to attract pollinators and give shelter for predatory insects, and you can plant vines to grow up the sides of the house in the summer to help with heat.
The biggest issue you will probably face with a greenhouse in the Pacific Northwest is humidity, which can cause mold and fungus issues. You will want to make sure that you have plenty of ventilation and air circulation to combat this. Drip irrigation and paying strict attention to not overwater will also help with moisture problems.
Spinach, kale, chard and other hardy greens can be planted in the fall and overwinter in the greenhouse. While it is cold and there is not much light in the winter, established greens may not grow much, but they should live through the winter and provide you with as early of a harvest as possible. You can do the same thing with other hardy vegetables such as leeks, carrots, garlic, onions, etc.
If you would like to just close up the greenhouse for the winter and not think about it, you can start seeds indoors as early as mid-January and then put them out three to six weeks later. If you start leafy greens this early, you will be able to replace them with another crop in late spring.
Most of the crops that you plant in the house in late spring are going to be those that you want season extensions for. Indeterminate tomatoes, cucumbers and peppers are all vegetables that will continue to produce well into the fall if you can keep them healthy and protect them from the elements. Many of the larger, bushing crops like squash and melons are probably better off outside, but you can use the greenhouse as a step in your hardening off process if you start indoors from seed. Make sure to also choose flowers and potted perennials that will grow well during each of the seasons. Having as much diversity and life at all times will benefit the overall health of the greenhouse.
It can be easy to just focus on the veggies and forget about herbs and flowers, but they both can help play an integral role in controlling pests; plus they look beautiful and smell great, so they are a bonus all around. Slugs, aphids and snails are the biggest pests in the PNW, but if you may know of others that are particularly bad in your area. If you’re new to gardening or new to your area, just ask any of your gardening neighbors what pests they most commonly come across. Whatever the pest may be, there is something you should be able to plant to help deter them. Things like basil, parsley, garlic and sage are known to repel slugs and snails, so you can plant next to things that slugs like to eat such as peas or cauliflower—this is called companion planting. Flowers like marigolds can be planted around the perimeter of the greenhouse to repel aphids.
If interplanting beneficial herbs and flowers is not enough to control your pest populations, you can try to purchase beneficial insects such as ladybugs, praying mantis, and predator mites. You can also make your own sprays with essential oils, or buy pre-made organic pest control sprays.
Done right an unheated greenhouse in the PNW should greatly increase your production and months of the year with fresh produce. Just make sure to keep it well ventilated, maximize crop diversity, watch out for pests, and most of all have fun.