Good morning gardening friends!
What a week of warm sunny weather Portland has had. Wow! The sunshine is good for us, our plants and our soil. However, please remember to keep your seed beds and new transplants watered in very well. New plantings don't yet have the established root structure to thrive in warm temperatures. You can assist them in reducing stress by making sure they are watered frequently until established. Also, if you've planted seeds for things like carrots, lettuce, etc. please keep your seed bed evenly moist to assist with germination. Tiny seeds find it difficult to germinate and sprout up through crusty dry soil. The seed bed doesn't need to be soaked, just evenly moist every day. Right now I'm watering my carrot seed bed once in the morning and once in the late afternoon/early evening.
In Portland our average last frost date is April 15th. This is important for gardeners because many seed packets and planting guides say things like "plant 3-4 weeks before last frost date or plant once all risk of frost is over." Could we still have a frost in Portland after April 15th? Absolutely! Is it likely this year given the nature of the warm winter and early spring? I don't think so!
Our nurseries and garden centers are filling up with sun loving summer veggies and herbs like tomatoes, cucumbers and basil. Just because retailers are selling these plants does not mean its time to plant them. Please keep also this in mind, just because our average last frost has passed does not mean the night temperatures are warm enough to plant your heat loving summer veggies and herbs. My general rule of thumb is, if you are wearing a sweater, using a blanket or your heater it is too cold outside still for summer veg. A more scientific rule is tomatoes need night temperatures consistently above 55 degrees. We have yet to reach night temperatures above 55 degrees, in fact they are averaging in the low-mid 40s. In Portland those ideal night temperatures typically arrive in mid-late May. This has been an unseasonably warm winter & spring, so perhaps they will arrive earlier.
Early planting of heat-loving summer veggies does not give you a jump start. If night temperatures are too cool it results in stunted or dead plants. Many years when there has been a warm snap in April I've planted my basil and a week later found blackened leaves and wilted plants when the weather turned cool again.
If you are interested in planting your heat-lovers with protection such a frost blanket, cloche, cold frame, greenhouse or wall of water/cozy coat, by all means go for it and have fun! I haven't invested much in season extenders, but that does not mean they aren't valuable tools in the Portland garden. Many gardeners have great success with pushing the limits on planting times with the aid of season extenders.
Friends, you know how much I love dahlias. I'm sorry to report it is also still too cool to plant your dahlia tubers. Dahlia tubers want soil that is consistently 60 degrees, often that is not until May in Portland. Take it from dahlia expert Mark Harvey of Old House Dahlias in Portland. This guy knows his dahlias!
Now that it is mid April it is a great time to plant seeds for sunflowers, runner beans, annual flowers. Sunflowers do great direct seeded into the warm mid-April soil. They are beautiful, make our bees so happy and in the fall provide a food source for our bird population. Here's some great information on growing sunflowers from our friends at Renee's Garden Seeds.
Both pole and bush beans are warm summer season veggies that we direct seed into the garden in May when temperatures are higher. However, the delightful heirloom runner bean is the earliest bean to plant in the garden. It can be direct seeded in mid April! If you haven't grown runner beans before you should, because they are awesome. They are a quick growing vine that produces edible pods and beautiful ornamental flowers typically in bright red. They can grow in sun or part shade, unlike other beans that require full sun. Hummingbirds love their flowers. This year I am growing 'sunset' variety that has pale peach flowers that I purchased from Baker Creek Heirloom Seed Company.
Mid April is a great time to direct seed for annual flowers. This week I planted seeds for nasturtium and 4 varieties of annual poppies. Lauren's Grape annual poppy seed is sure to wow you! Make sure to keep your seed beds evenly moist.
For the remainder of April I would continue to plant your cool-season veggie crops. Here's the link to the handy veggie planting calendar from our friends at Portland Nursery.
Brussels sprouts-for fall harvest
Parsnips-for fall harvest
Peas-sugar snap, snow & shelling
Salad greens-arugula, cress, endive, escarole, mache, mesclun mix & radicchio
Herbs: Most herbs would do great now-cilantro, chamomile, chives, dill, mints, oregano, rosemary, sage, thyme.
WAIT until the warmer temperatures of May to plant your warm-season veggie crops:
Beans-pole & bush
Melons & watermelon
Tender herbs need warmer temperatures: BASIL, lemongrass, shiso. Also, tarragon can be a little fickle in the cool wet spring.
Have fun and please let me know if you have any questions. I hope to see you soon in a gardening workshop or neighborhood gardening group.