Getting gardens ready for fall
It’s the season for harvesting and planning
Washington Post Gardening columnist Adrian Higgins answered questions recently in an online chat. Here is an edited excerpt.
Q: I’m looking to plant fall vegetables that I can harvest either later this winter or spring. I have thought of garlic, onions and kale as options that will weather the winter, and peas, spinach and arugula as options that will grow this fall. Suggestions? A: If you can find transplants of cabbages and broccoli, now is a good time to plant them. For other brassicas such as arugula, mustard greens, kale and collards, now is a great time to sow seed. They will grow quickly and provide a frost- (but not freeze-) tolerant harvest until the end of fall. You could sow onion seeds now for harvest next summer. You could also try peas, but it’s getting a bit late. I would soak them for a day or two before planting. Plant garlic in October.
Q: We have a mature willow oak with lichen growing around its trunk. Is this something that needs to be treated to keep the tree healthy, or is it normal?
A: Lichen is one of the great ornaments of the garden and does no harm to its host plant. It is also an indicator that you live in an area with unpolluted air. Rejoice.
Q: This is our second summer in our home. We recently discovered our backyard neighbor has an abandoned water feature. The plastic liner is still in decent shape and retains water – which we’re pretty sure is the source of our yard’s mosquito problem. Because we can’t control when or if this liner gets removed, is there anything we can do in our own yard to discourage mosquitoes?
A: Shallow standing water will produce mosquito larvae, and your neighbor has a civic duty, in my view, to stay on top of this. The short-term fix is to put mosquito dunks in the thing; the long-term answer is to either get it working again or remove it. Mosquitoes won’t breed in running water. In other cases, fish will eat the larvae.
Q: Wild strawberries have taken over our lawn and invaded our perennials. In previous years we have been able to keep them under control. Do you have any advice on removing them from the lawn and the perennials? Also, is fall a good time to transplant perennials?
A: There are herbicides that will control them, but I prefer the more laborious approach of digging them out. You can use a fishtail weeder or weeding knife. In my experience, wild strawberries grow in the vacuum of a thinning lawn, so after removing them, you should overseed the lawn. The next few weeks are the perfect time for lifting and dividing perennials that need splitting; the top growth has done its work for the season, and the roots and crowns can get over transplant shock and develop during the mild fall.
Q: I planted a passion fruit vine last year. I thought it died last winter, but it has reemerged with a vengeance and is taking over the flower bed. It also has runners popping up in the lawn. Is there a way to control the spread next year? Should I dig it up and plant in a large container?
A: I think the native, hardy passiflora (Maypop) is known to spread. Yes, dig it up and put it where you want it.
Q: Is this a good time to use Holly-Tone and on which plants?
A: You don’t want to use any type of high-nitrogen fertilizer at this point on woody plants because it will induce tender growth. I would wait until early spring.
Q: Some areas of my backyard were torn up by construction work and I need to reseed. When should I do that? Will I need to water every day? This summer’s weather is either superhot or stormy, so I’m worried the grass seed will either die of the heat or get washed away. A: We are entering the window for cool-season grass seeding, but for this to be successful, the beds should be prepared. The seeds need continual moisture (not constant soaking) and good seed-to-soil contact. This is why it is best to tamp or roll the lawn after seeding. You will have to spray the seedbed daily.
Q: We have a viburnum that we transplanted successfully a few years ago and it has thrived, but this year all the leaves browned and dropped off. The bush next to it is doing fine. How do I tell whether it’s dead? What might have happened?
A: This is probably a symptom of the excessive rain this summer, which has caused a number of leaf disease issues. As long as the stems are alive (scrape to find green cambium), it should leaf out all right next spring. Clean up the fallen leaves.
Q: I have a row of boxwoods that were previously shaped into a curved row with a flat top (approximately three feet high). However, the previous owner cut the new growth on the tops and sides, meaning that the inside of the plants is pretty barren because of a lack of light and air. I plan on thinning the plants to allow better interior growth. Any tips or advice? A: You might be able to shear boxwood in northern climates, but not here. One of the problems with shearing is that you create a lot of surface foliation but little within the bush. Instead, prune out dense growth to open up the surface of the shrub. These holes will soon fill in, promote deeper growth and improve air circulation.
Q: I have a long row of azaleas that were planted by the previous owner along the back wall of my house. They receive an intense amount of sunshine and radiant heat from the bricks on the house and don’t do well for much of the year. I’d like to rip them out this fall, rebuild the beds and replace them with something (ideally with some color) that can handle the heat. I thought this would be a fairly common request, but it seems to have stumped a lot of nurseries. Any tips?
A: The azaleas can be moved into a shady areas; they move quite well because of their fibrous roots. You can use a mix of plants to replace them. They don’t have to be all the same thing. I would consider a blend of sun-loving shrubs (dwarf crape myrtles and abelias come to mind), perennials and grasses. September is the month to do this.