Washington Post Gardening columnist Adrian Higgins answered questions recently in an online chat. Here is an edited excerpt.
Q: Where do you recommend beginners learn fundamentals of gardening?
A: I don’t think you can learn gardening from online sources, and even books have their limitations. The best way to learn how to garden is to do it, and preferably in the orbit of a friend or relative who is a gardener and can guide you. This is why a community garden can be so helpful.
Q: How can I safely treat an indoor, potted basil (to be used for cooking) for little flying bugs?
A: Sounds like whitefly. If you have a severe infestation, I would bag and throw out the basil plants and buy some fresh plants. They also will be much happier growing outside.
Q: My son and I are starting a butterfly garden in our yard. We know milkweed is important for caterpillars and butterflies, but every nursery we’ve gone to says that they don’t have it and that it’s not something garden stores sell. How and where do we acquire some for our garden?
A: Milkweed species are fairly easy to find. It would have been better to have bought some plants a month ago at local nurseries or plant sales. You may find seeds but it’s too late to grow them from seed and expect a good result this year.
There is controversy about planting the tropical milkweed. Some believe it is sickening monarchs, leaving three perennial milkweed species to explore. I think swamp milkweed is prettier than butterfly weed. The common milkweed (Asclepias syriaca) is just too weedy and coarse for the home garden in my view.
Q: I had to rip out a bunch of the landscaping in the front of my house after a fire and restoration. I’m moving back into the house mid-July. Should I wait until September to plant dwarf boxwoods and replace the Japanese maple tree that also was a casualty?
A: I would only plant now (with summer’s heat) if you have done great soil preparation, the roots are gently, but effectively, teased out of their pot shape, you put down a thin layer of organic mulch, and you are planting in an area of partial shade. Most boxwood varieties, in particular, do much better in partial shade than full sun. After setting a plant in the ground, it’s important to water it well and then push the soil down around the roots to eliminate air pockets, refilling the depressions as needed.
Q: I’m getting bored standing outside and watering my raised beds. Can you suggest a robot option? How about a sprinkler that clips onto the bed?
A: I might use a drip irrigation system, but I generally don’t like automatic irrigation systems for many reasons, not least because hand watering requires you to see how your plants are doing. Sprinklers can cause all sorts of foliar disease problems.
Q: I had a crazy spring and missed planting my herb/vegetable garden. I want to put in basil, oregano, thyme, onions and jalapenos. Is it too late?
A: You can still plant transplants of all those things except the onions. You could grow onions from seed in August for overwintering and harvest next summer.
Q: I purchased a Sungold tomato seedling at a market a couple of months ago and it has been growing well. It’s already almost 6 feet tall and escaping its 4-foot-tall cage. I had never grown this variety before and didn’t realize they can grow to 10 feet. Do I need to do anything else to make sure it is supported as it continues growing?
A: Sungold is a robust vine and a tomato with great flavor. I might consider building a tepee or tripod with eight- or 10-foot lengths of bamboo or stakes. You’ll need a step ladder and a good mallet to set the stakes. Most ready-made tomato cages are woefully too small for the job (though useful for pepper plants).
Q: Should the Sungold tomato plant owner consider pinching back some of the topmost growth to encourage greater bushiness? Or is it not that type of tomato? We do this with indeterminate tomato plants, in the belief it encourages fruit yield.
A: When the tomato plant is young, up to half-grown, I pinch out the suckers that appear in the axils of the leaves. This keeps the plant upright and from sprawling. Once the plant is at a certain height, I don’t worry about these axil suckers and let them develop because I want the plant to have a lot of leaf coverage to produce sugars and to shade the fruit.
Q: We have a well-shaded back yard and are looking to disguise the back fence. Do you have a recommendation for shrubs/bushes or a small tree that would do well in the shade and give us coverage?
A: I think American holly varieties would work. I really like a different holly named Ilex x koehneana, which isn’t used enough. It’s big and like most other hollies, will need a male plant to support berry production.
Q: I am against Roundup and have heard boiling water can kill weeds. I am skeptical though. Do you have any thoughts?
A: Boiling water may kill the weed outright or just the top growth, and it will resprout. It also will kill all of the life in the soil, so I’m not sure I would do that. I only remove weeds by pulling them or cutting them out of the ground.
Q: I’ve planted a number of edibles (tomatoes, green beans, okra, etc.) from seed and seedlings in our back yard. If I add compost every few weeks, is there any need for additional fertilizer? Also, I planted a few edibles in used car tires sitting on the ground (easier raised “beds” than traditional raised beds). Should I have any concerns about leaching chemicals?
A: In terms of feeding, I add dry organic fertilizer and lime into the planting hole at planting time, mixed well into the soil, and then mulch the plants with straw.
As they grow, I feed every three or four weeks with a fish/seaweed liquid fertilizer. I would not grow edibles in tires. The champion of this, in England, is Bob Flowerdew, of whom I have written, but I would not be confident that the rubber, etc., is going to be safe.
Q: I purchased two “Bearss” lime trees and will be potting them for a summer on the patio. Living in a harsh Western climate, they will winter indoors. Any advice for a first-time citrus grower?
A: The best way to winter citrus indoors in the winter is to give them a cool room (50s, 60s), plenty of light and try to keep the humidity at a reasonable level. Look for scale insects and remove them with swabs of rubbing alcohol. You may have leaf drop but they should refoliate in the spring. I would give them a little shade outdoors.
Q: I have a small garden and have not rotated sufficiently. I still get a good crop of tomatoes most years, but the wet weather brought on Septoria spot quite early. What’s your opinion of Serenade spray? Or should I remove the affected leaves and hope it can outrun it?
A: We are at a critical juncture in terms of checking early blight disease (Alternaria), which is seen on lower leaves as they yellow. It’s important to remove those as soon as possible and without touching or infecting the upper leaves. I don’t spray, though I suppose that’s an option.
Q: I have a lovely raised bed in the back yard of my 60-year-old home. I think the house’s former owner used it for a vegetable garden, but then she planted a dense evergreen tree. The bed gets about four hours of sun a day and some filtered sun in the morning. Can I grow herbs there?
A: Many herbs are Mediterranean plants that like bright light. You could try some mint varieties and maybe some oregano and lemon verbena, as well as scented geraniums.
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