Adrian Higgins on summer gardening

Courtesy of Rutgers University
Jun 14, 2018

Washington Post gardening columnist Adrian Higgins took questions on gardening.

I received a potted Hydrangea plant as a gift and would like to plant it outside and was told I should. Is there anything special I need to do? I've never had a hydrangea before. I was thinking of the front of my house which gets a ton of morning/early afternoon sun.

Greetings everyone. This prolonged period of abnormally wet weather will have its pros and cons. At the moment, we are enjoying its resulting lushness, but there may be delayed problems with rotting roots and stuff. Anyway, to the question at hand. Most potted hydrangeas are greenhouse grown for use as tabletop plants. They are not necessarily the best garden plants. While they may be hardy in Washington, they probably are not in colder regions. Nor are they bred for disease resistance. You can try it in the garden and see how it does, it will need a location with partial shade (shielded from the sun in the afternoon) and in enriched soil that retains moisture. Water it when it gets dry. 

Hi, producer here with a link to Adrian's most recent column, on rambling roses. Check it out here.

Hi Adrian, My wife and I are first time homeowners of a row house in Alexandria and the previous owner of the house had laid asphalt for a driveway from the back alley to the house itself. While we appreciate having the extra parking spot, we want to cut the driveway in half, pull up the asphalt, put in a fence and turn it into a nice little backyard. With that in mind, I have two questions: 1) This seems relatively straightforward in principle, but what are the potential pitfalls I should keep in mind? 2) The garden space will be about 10 x 20 ft. What tips do you have for making the most out of the relatively small space?

First, I would allot more time for this job than you think it will take and don't rush yourself. And buy a couple of sturdy mattocks. The asphalt may have a sublayer of gravel or some other material, which will need to be removed as well. The soil will be compacted, and may just be lifeless subsoil, so you will need to bring in a lot of loam, organic matter -- that can be Phase 2. The other issue is that the soil may be contaminated by the asphalt itself or fluids from vehicles that have accumulated over the years. So I would not grow any edibles there, and you might want to get a soil test, including for lead. As for maximizing space, the way to do that is to grow vines and tropicals in pots, anything that will have a strong vertical presence and actually hide the edges of the patio.  

My son and I are starting a butterfly garden in our yard. We know that milkweed is important for caterpillars and butterflies, but every nursery we've walked into says they don't have it, that it's not something garden stores sell. How/where do we get some milkweed for our butterfly garden? Thanks!

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 now 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 species to explore. I think swamp milkweed is prettier than butterfly weed. The common milkweed (A. syriaca) is just too weedy and coarse for the home garden, in my view. 

So I had rip out a bunch of the landscaping in the front of my house after fire and restoration. I'm moving back into the house mid July. Should I wait until September to contemplate planting say dwarf boxwoods and replacing the japanese maple tree that was also a casualty?

I would only plant now (with summer's heat at the door) 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. 

Can you suggest a robot option? How about a sprinkler that clips onto the bed?

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. 

I had a crazy spring and missed planting my little herb/vegetable garden. I want to put in basil, oregano, thyme, onions, and jalepenos. Is it too late to do it now?

You can plant transplants of all those things except the onions, there's still time. You could grow onions from seed in August for overwintering and harvest next summer. 

I purchased a sungold tomato seedling at a market a couple of months ago and it has been growing well - very well in fact. It's already almost six feet tall and escaping its four-foot-tall cage! I had never grown this variety before and didn't realize that they can grow to 10 feet. Do I need to do anything else to make sure it is supported as it continues growing?

Sungold is a robust vine and a tomato with great flavor. I might consider building a tepee or tripod with eight or ten 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).  

Good day, 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 the cover? In Anne Arundel County so very sandy soil with good drainage, property is west facing. Thank you.

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.   

I am steadfast against Roundup and have heard that boiling water can kill weeds. I am skeptical though. Do you have any thoughts on the matter, please?

Boiling water may kill the weed outright or just the top growth, and it will resprout. It will also kill all 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. 

Hi Adrian, I know next-to-nothing about gardening, but it doesn't stop me from trying! Where do you recommend beginners learn fundamentals of gardening?

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/relative who is a gardener and can guide you. This is why a community garden can be so helpful. 

In our backyard in Silver Spring, I've planted a number of edibles from seed and seedlings in our backyard. (1) If I add compost every few weeks is there any need for additional fertilizer, for tomatoes, green beans, okra, tropical gourd, zucchini? (2) I planted a few edibles in used car tires sitting on the ground (easier raised "beds" than traditional raised beds) - am wondering if I should have any concerns about leaching chemicals?

In terms of feeding, I make sure that 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.

To the chatter asking about milkweed: Chesapeake Natives is having a native plant sale June 24th in Upper Marlboro (http://chesapeakenatives.org/plant-sales/), and they have swamp, purple and common milkweed on their list for sale.

Perfect, thanks for the information.  

Should its owner consider pinching back some of the topmost growth in order to encourage greater bushy-ness? Or is it not that type of tomato? We do this with our indeterminate tomato plants, in the belief it encourages fruit yield. Or are we mistaken?

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. 

Hello, I would like to say thank you for participating in these chats. Over the years my garden has been transformed from an over-watered, overgrown, ground level, scraped earth garden to 3 foot raised bed, not over-crowded, and hand watered hobby. I refer to your advice often and look forward to these chats. I purchased 2 Bearss lime trees on a whim this week and will be potting them for a summer on the patio this weekend. Living in a harsh western climate they will winter indoors. Do you have any advice for a first time citrus grower?

Sounds terrific. 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. 

I have a small garden and have not rotated sufficiently. I still manage to 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--worth the bother? Or should I just remove the affected leaves and hope the plant can outrun it?

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 very important to remove those as soon as possible and without touching or infecting the upper leaves. I don't spray, I suppose that's an option. Any other tips out there? 

Hi! My first season growing sunflowers from seed. They are growing prodigiously, and have reached about waist level over the last 6 weeks. However, while mostly healthy, they appear to have some strange holes in the leaves, along with some crinkly browning. Is it a pest? Too little water? What can I do to help them out?

The one thing they don't need is wet soil, especially after all this rain. I would remove brown leaves but leave the holed ones. Flea beetles are a problem on young plants, especially eggplant and peppers, but a well tended plant will usually outgrow the damage. I think that's also the case for your sunflowers. Don't give them a high nitrogen feed and only water when they are dry. 

we had bushes in front that were taken out, leaving the stumps and roots. Then we got ground bees. We've covered the bees with tarps--following advice on line. When the tarps come off, what do we do? I've been thinking that mulch with containers--but what to put in the containers? Space faces east with morning sun.

I'm not sure I would have followed that advice. Ground bees may be scary but generally are quite harmless if left alone. The tarp will kill a lot of the soil biology through solarization. Another big issue with tarps is that they all trap puddles of water which become perfect breeding grounds for the Asian tiger mosquito. I'd rather have the bees. 

What can I do for an indoor, potted basil (to be used for cooking) to safely treat for teeny little flying bugs?

Sounds like whitefly. If you have a severe infestation I would bag and throw out the basil plants and buy some fresh plants. They will be much happier growing outside, by the way. 

I have a lovely raised bed created in the backyard by the original owner of my 60 year old home. I think she used it for a vegetable garden, but then she planted an evergreen tree that is pretty dense, and in general, all the trees in the area have now grown very tall. So the bed gets about 4 hours of sun a day, and some flittered sun in the morning. Can I grow herbs there?

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. 

What's the name of that rose? Do you know where the photo was taken? You mentioned 'Dr. Van Fleet' and 'New Dawn'. "Awakening' is another Van Fleet sport well worth having; it has fuller flowers than 'New Dawn'.

The rose on the cover is Dr. W. Van Fleet. This was in the Stafford County, Va. garden of rosarian Connie Hilker.   

Is there some sort of climbing plant or vine that would do well to cover a trellis/fence in a planter with full sun? Any that would be green year-round?

Maybe Clematis armandii. Alas we have run out of time. See you here soon.

In This Chat
Adrian Higgins
Adrian Higgins is The Washington Post's gardening columnist. Read his latest columns and stories here and follow him on Twitter.
Recent Chats
  • Next: