Adrian Higgins on the Bradford pear, and all things gardening

By Jennifer Heffner For The Washington Post
Sep 24, 2018

Washington Post gardening columnist Adrian Higgins took questions on gardening.

Professor, I have a special spot in my garden where I'd like to plant a real showstopping evergreen. 6' high x 4'wide max. The area gets a good 6 hours of sun per day. Do you have any places in the DC/VA/MD area where you like to shop for out-of-the ordinary conifers? I've visited a few nurseries in Northern VA but haven't seen anything but the usual suspects.

Greetings all. The chat is prompted by my weekend story in the Magazine about how the Bradford pear became so invasive. But this is a key moment in the gardening year, and so we are taking questions on fall gardening. I don't like to give a specific nursery, because there are so many in Greater Washington alone that I know I would be missing some. It sounds like you need a semi-dwarf conifer, of which there are many beautiful varieties. Some of the eastern white pine cultivars are truly pretty. I would contact the regional chapter of the American Conifer Society to get you started on plants and sources. http://southeast.conifersociety.org/

Producer here, with a link to Adrian's latest story, on the Bradford pear.

I planted a Bradford Pear (considered great for urban parking strips) in the early 1980s in Portland Oregon. What is the best thing to do now? Ignore it or remove it? Or is this something to be determined by what part of the country the tree was planted in? Thank you! Michael S

If there are no other callery pears in your vicinity, it may not be a problem. I have to say if you have an old surviving Bradford pear, its presence isn't going to make a huge difference to the escaped population at this stage. I might take it down simply because it has become old and unattractive (and I would be worried about storm damage).

Hey, In reading this article it slowly dawned on me that the 40 odd beautiful trees that line my neighbour's long driveway are all Bradford pears. I'm in Sydney Australia, and next to a natural bushland that they may have been spreading into for years. What actionable steps do you think I could take?

They are self sterile unless they are close to another callery pear selection or their rootstock has begun to sucker and bloom. I think there are very active native plant groups in Australia, I would check with your local native plant society to see if it's an issue. 

Hello, we were sold on the beauty and practicality of this tree by our own Medford planning department, which selected it as a street tree. They do grow columnar downtown, but in our front yard, we took care to cut out all high-angle branches as it developed. It has grown since '92 into a beautiful spreading tree with elegant foliage, good shade and all the brilliant fall colors you describe. We receive many compliments on it. Now, we're heartbroken to discover we may be harboring an arboreal felon! We have pear orchards within a mile of our property, with which it might conceivably hybridize, but we have only ever seen small, round inedible fruits. Ought we to remove it? If so, what "safe" tree might fill a similar-sized role in this region, especially given the trend to hotter, longer summers?

I don't think the Bradford can be pollinated by the European edible pear. (Pyrus communis). My aim certainly isn't to get people to remove existing Bradford pears if they are healthy and intact. As I say, I think the horse is out of the barn at this point and removing your landscape tree isn't going to make much of a difference. 

I have some volunteer trees that I thought were crab apples, but now worry might be callery pears. Can you tell me how to be sure from looking at the tree and or fruit?

I didn't know this until recently, but crab apples can escape into the wild, particularly in the Northeast. Bradford pear fruit is a green-tan color, and russeted. Crab apple fruit tends to be smooth skinned. The best indicator is bloom time. Around here, the Bradford pear flowers in late March, the crab apple in mid April. 

Thank you for hosting your live chats; I always enjoy and learn from your columns! If all things gardening includes the insects who live there, I have a question for you. I have not one, but two orb-weaver spiders residing in my garden. Not a lover of insects or arachnids, I freaked out when I first noticed them, but have since learned that they can be beneficial to the garden by taking out harmful pests. However, I've also seen them take out beneficial pests - pollinators like butterflies and bumblebees. What's the consensus? I suppose that the cooler temperatures to come will take care of the issue soon, but for future reference, what's the best way to deal with these enormous spiders?

This is the time of year when spiders are big and very web savvy. I love to see argiope, garden and orb-weaver spiders at this time of year. In the garden yesterday I disturbed wolf spiders of enormous size, like mini-tarantulas. If the webs are not in the way, please leave them alone. If the web is in the way, you can gently remove it with a stick and the spider will find another place to weave a web. 

I posted in your last chat about my Black Lace Sambucus suddenly dying, but I see that now that most of the leaves have dropped off, there are several leaves still apparently alive at the very top of the tree. Should I take the tree down anyway? I can't imagine what it will look like next year if it's not quite dead...

We are seeing a lot of defoliation this month due to the heavy rainfall. My advice is to leave it alone and see what burgeons next spring. At that point you can see dead wood and remove it, or know if the entire shrub or tree is dead.   

I have a beautiful amsonia clump that has outgrown its space and needs to be moved. Do I move it now or wait til next spring?

Now would be a good time to move it. 

Our whole neighborhood here in Frederick was planted with the trees in the 1970s. Starting in the 2000s after every bad storm the sound of chain saws sang throughout the area. They are such soft wood that big branches and whole trees would fall. We finally got rid of them, as did almost all our neighbors. When my daughter and husband bought their house in VA there was a Bradford pear in the back yard. She gave it the evil eye and announced to her husband we can by this house as long as that tree goes.

Your daughter is a wise and discerning woman. 

Fabulous article on the Bradford Pear problem. While I don't have Bradford pears my backyard was invaded while the restoration of my house took precedence. Vines of many varieties, pokeweed and some mysterious ten foot tall weed where my tomatoes once grew. I suppose I need to keep up my Washington Post subscription to use the paper to block the weeds from coming back next spring.

Yes, keep those paper subscriptions coming. You're talking to the ultimate Analog Man, here. As for your weeds, vines tend to be the most destructive invaders because they put their energy into soft growth, not making wood, because they lean on other plants. This year has been a banner one for them simply because of the excessive heat and rainfall. Cut them back, and then use a mattock to attack the roots. This can be done at any time as long as the ground isn't frozen. Make sure you identify the vine and take precautions against poison ivy etc. 

Do you have online sources you can recommend for purchasing perennials? Also, thanks for the great article on the Bradford pear invasion!

This is a constant problem for me, as well. I wish more wholesale growers would make their plug plants available to consumers. Independent garden centers seem to have a fairly good selection, if in big sizes at big prices. Local plant sales are a great way to discover specialty perennial and shrub growers who sell directly to consumers. 

How are the selections made? I cannot believe the number of Bald Cypresses I have lately seen newly planted in all kinds of areas--from the Palisades along MacArthur to the almost unrelievedly asphalt and concrete canyon lands of the Farragut North area. Is there no Humane Society for plants? Thank you.

Street trees have to put up with both drought and flood (as well as awful soil), which is why the range of suitable candidates is pretty small, and they tend to be bottomland trees such as bald cypress. Casey Trees is an excellent resource for finding street trees by size and characteristics. https://caseytrees.org/tree-species/

Hi Mr. Higgins, I have a south facing balcony and would like to try growing lavender next spring. Do you have any advice on planter size and/or cultivar selection? Thanks very much!

Generally, the larger the container, the easier on the plant. So don't go with anything less than 12 inches, and make sure you have incorporated lots of grit or gravel into the mix and everything is free draining. Lavandins are bigger than angustifolias, but might be a little more tender. Any plant in a container will need to be a zone or two hardier than those in the ground, because their roots are less insulated against winter cold.  

I got some wildflower seeds and want to plant them in the fall (they're an annual/perennial mix). I guess I need to get them in at least a couple of weeks before the first frost and also keep them wet for 6 weeks at the beginning. Can/should I plant them this week in all this wetness? Not sure about my timing...

Establishing wildflower meadows, beds is so much more than sprinkling a few seeds. You have to figure out how to get the seedlings established under enormous weed pressure, especially in disturbed soil. Larry Weaner is an expert on this, and I'd direct you to his website: http://lweanerassociates.com/?page_id=14

Can we use aerial photography to scan for their blooms and mark them on a map for eradication before they seed?

Even if you identified them, the challenge would be to kill them, which is what Carole Bergmann is trying to do through a multi-year program of mowing in the spring. This weakens them without disturbing the soil, which would simply invite other invasive plants to grow.  

Hello. I have a row of decorative liriope at the edge of a flower bed that has been overtaken by Bermuda grass. Manually pulling the Bermuda grass is not working. Do you have any advice? Suggested herbicides? Thank you.

There are herbicides that will kill wiregrass, which may need several  applications through the growing season. You would have to apply a general purpose weedkiller, which would zap everything else in the vicinity. I find it can be pulled back, a task made easier by the wet soil we have at the moment.  

My neighbors have built an abomination of a house next door and I'd like to layer some screening between our yards. I was hoping to get away from arborvitae and looking for something with some seasonal interest that can also grow to a height of 10-15 feet. I was thinking of skip laurel but was curious if you had any native preferences.

I might go with some varieties of holly, and you can pick native types if you want, such as American holly or Yaupon. If you want non-native evergreens, I might consider chindo viburnum or Korean pine. 

Good afternoon! I have never been able to plant hydrangeas bc of the deer that feast in my yard daily. This fall, I've purchased 2 very large pots (30" diameter) and placed them on my patio, where they will receive morning sun and afternoon shade. Do you have any favorite hydrangeas I should be considering?

The big trend in hortensia hydrangeas is with the freeze hardy rebloomers, but I must say I like some of the older varieties, such as Blue Bird and Tokyo Delight. 

I’m looking for a moderate size shade tree for the back yard. I’m considering the American Horn Beam. How much space from fence and deck would I need to plan? Are there other trees I might consider? I’m in upstate (Rochester) Bew York. Sandy soil, south east exposure

The American hornbeam is a lovely native woodland tree, I'm not sure it would be happy in full sun. A related tree is the hop-hornbeam, that's a great choice for a sunnier location. Ostrya virginiana, hardy to Zone 4.  

This came up in the food chat last week. True or false? I should not compost tomatoes. Compost does not get hot enough to kill any diseases that might affect the plant. Or is this do not compost tomato PLANTS, not the fruit itself? Thank you!

There are two basic types of compost, the active, hot pile and the passive one that just breaks down over a much longer period. The former takes work and method but temperatures will reach 150 degree F. which is pretty good at killing weed seeds and pathogens. I wouldn't fret too much over adding tomato stuff.  

I think this every time I drive by public plantings and see trees buried in mulch. I wish trees could scream. Can we form a mulch vigilante crew and attack this problem?

I think we need to invent a tree screaming app, which will give voice to these immobile victims of mulch volcanoes. 

For the earlier comment - I recently re-did a large bed in my garden with the help of a landscape designer. I was able to get most of the specific perennials he suggested at local stores plus one an hour drive away, but there were still some plants I had to get online. I used Bluestone Perennials (www.bluestoneperennials.com) and was very pleased with the plants they sent. They shipped them at the right time for my area and they came with great instructions. They seemed very healthy and have so far done very well.

Sharing this, thank you.

I planted a rhubarb rhizome in March which had been doing splendidly all summer. Suddenly a few weeks ago the 5 stalks and leaves all went limp and withered away, leaving no aboveground foliage. Is it worth leaving the rhizome in place to see if it comes back next spring? Any idea why it may have suddenly died back?

Rhubarb is a plant that likes even moisture, but not wet soil. It is very unhappy in our hot, humid climate and prefers northern climes. The best way to get it going, I'm told (because I've failed many times) is to take a division now (not spring) and plant it in organically rich but free draining soil with the crown a couple of inches proud of the soil line. This year's flood has been deadly for so many things. Thank you for all your question and sorry I couldn't get to them all. See you here soon again.

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Adrian Higgins
Adrian Higgins is The Washington Post's gardening columnist. Read his latest columns and stories here and follow him on Twitter.
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