Adrian Higgins on gardening

Courtesy of Rutgers University
Nov 30, 2017

Washington Post gardening columnist Adrian Higgins took questions on gardening.

Adrian, Two questions: I have a tall Holly next to my house 20+ft, I would like to take about 1/3 off the top, what is the best time of year to make a cut of this size? My rain culvert is being overtaken with green kyllinga, it is also spreading into the main lawn are the off-the-shelf offerings by ortho etc... for yellow nut sedge effective? Thanks FFX Station

Hello, all. Although the holiday decorations are going up, I'm still enjoying the autumn moment. In spite of a less than spectacular display of tree color this year, the oaks have come from behind to produce unusually intense and lovely colors, oranges, russets, and golds. Take a moment to look at them. Holly generally will respond to pruning well, and I have seen many clipped hedges of American holly, Burford holly, Yaupon holly and Nellie Stevens. You could remove the top now and any time before spring growth but be aware that you may end up with a suckering mess at the top as a result. You should select the strongest, dominant sprout and remove the rest if you want to return a central leader.  Nutsedge is a persistent weed because even when you pull it, the little "nuts" in the soil resprout. You can apply an herbicide formulated for yellow nutsedge. I have a problem in my garden paths. I cut them back as they emerge. Don't let them grow to seeding size/stage.

Producer here, with a link to Adrian's most recent story, on the rise and fall of ivy.

Hello Adrian, very much enjoyed your story about ivy in today's Post. We have ivy along a bank in our front yard and it serves as a great ground cover, BUT it is more maintenance than I anticipated. It's very hard to weed and tends to "travel" into our lawn. Is there anything else that works as well? Or should I just resign myself to the fact that any ground cover we plant there will take a lot of maintenance?

Thank you. We'll post the link to the story. There are many groundcovers you could use instead of ivy that wouldn't need the constant clipping. Epimediums, sedges, mondo grass, leadwort are among some options for shady areas. Ferns too could work, although they are obviously not as tidy. 

Hi Adrian, my question is about the timing of repotting plants. I have a pencil plant that lives on the deck in the summer and comes inside for the winter. It has clearly outgrown its pot and needs to be planted in a larger one, but I'm not sure if I should do it now or wait until spring. If I do it now, will that encourage more growth while it's inside? I don't want it to get any bigger than it already is. Thanks!

Typically, you don't repot at this time because you want the plants to go into a dormancy and rest before their spring growth. However, I think if the plant really needs it, anytime is a good time, that is, if  it is clearly potbound to the point where the roots are blocking the drainage hole and you can't slip it out of its pot. One thing you can do to limit vigor is to take some scissors and trim back some of the roots while you are repotting. 

I am thinking about buying bulk compost out here in the country as I have a lot of lovely Virginia red clay I'm trying to amend and lighten. What should I look for at a vendor's site? How can I be assured that the ingredients don't contain pesticides or other inappropriate amounts of sticks, rocks, etc?

The obvious thing is to look at it, smell it, feel it. And ask what's in it. You want to avoid anything made with soil, which may be disguised by fluffing it up with some mulch or the like. I would take a handful, squeeze it, and if it forms a ball, move on. There is the risk of bulk compost containing residues of pesticide. That's harder to detect. Again, ask where the source material is from. 

I have blackberries and black raspberries; I also took advice from you and planted kiwi vines two years ago, and they seem to be doing well (no fruit yet of course). Should I water these occasionally over the winter, especially in these dry and warmer-than-average stretches?

These brambles only need watering if they are newly planted. Otherwise I wouldn't worry about it, assuming they're not in sandy soil. You should remove the old fruiting canes but leave some of the canes that grew this year -- they will bear next year's fruit. They can be cut back to a couple of feet and thinned out if needed before spring growth. 

Good afternoon, last week a neighbor offered several healthy forsythia bushes with the root balls intact. Is it too late in the season to replant them? I thought it was but wanted to double check. Thank you very much.

You could plant them now. Forsythias are valued in northern states for providing a splash of color after a long winter, but in these parts there are so many superior flowering shrubs for late winter, early spring,  deutzias, corylopsis, witchhazels, quinces, etc.

Adrian, I found your story about efforts to tame ivy in the Rock Creek Park area quite informative. However, isn't ivy also a problem for buildings? If it grows up the side of our house, doesn't it damage the mortar in the brickwork? Or is it not a problem?

Ivy will damage old, soft mortar. Mortar on newer homes is harder and generally ivy proof. There are other issues of retaining damp and getting into eaves and fascias. On the plus side, a vine would protect a structure from the sun and provide nesting sites for birds. 

Hi, I have quite a few ornamental grasses in my garden and am trying to decide if they should be cut back now or to wait until early spring. They look a little messy, but on the other hand they are attractive in other ways, especially when it snows. Is there an optimum time to cut back grasses?

If the grasses are lodged, the term for being flattened by wind and rain, I would cut them back now. If they are just a bit wayward, I would keep them. They can look really good emerging from the snow. All grasses should be cut back hard before new growth appears in the spring. Don't wait until April. 

Hi Adrian, what is your recommendation for fresh materials for a Christmas wreath? I like the idea of incorporating ivy (which you wrote about today), but what do you think is the longest lasting? Boxwood? Fir? I'm debating whether to order a pre-made fresh wreath or make my own.

I think if you're using live material, boxwood is the best. Though I would soak it in an anti-desiccant first. Putting the sprigs in damp oasis will keep them going longer, as will their placement outdoors. Behind a glazed storm door, they will cook, btw. 

All summer long, I said to myself that I must repot that Christmas cactus that's getting so leggy...but I didn't, and now it's budding. Should I leave it in its pot until it stops flowering or can I repot it now?

Don't repot if its about to bloom. Wait until after it has flowered, and then let it rest for a few weeks. It will need another period of rest (minimal watering, no feeding) later in the year to induce reblooming.

Is there any way that I can plant spring bulbs -- crocuses, snowdrops, and so on -- and NOT have the dratted neighborhood squirrels dig them up and eat them? It annoys me no end to see those sad little holes that HAD contained such promise.

Crocuses in particular seem a real target. My advice is to plant deeply and then put a layer of mulch on top. Squirrels are drawn to visibly disturbed soil. One year, I put netting between the soil and mulch, but the squirrels still got to many of the bulbs. Has anyone had luck with repellents? 

Please share that ivy can cause a terrible skin reaction--as bad as poison ivy in my experience. On a related note, please remind gardeners/home owners to practice responsible gardening and not let the stuff encroach on neighbors. It's bad enough that it harbors rats and mosquitoes, having to remove it is a big pain! It may be attractive in some applications, but seeing it strangling so many trees makes me wish more garden centers would ban it. It's not like we will EVER be rid of it.

Some people find it to be an irritant. If you are ripping it up, I would wear thick gloves and, possibly, a face mask. The thing that harbors mosquitoes more than anything is standing water.  

Your column today has so much good information. Would you say that it's ok to plant an ivy to grow up a brick wall? Does Ivy damage the mortar? I have a brick wall that is nearly fully shaded. Would an ivy cover damage the wall? I am a serious gardener and would keep the ivy under control and tamed.

I think there are some rare circumstances where I might plant a variegated ivy on a dark wall where little else would grow, but only because I know that I would keep it caged, so to speak. Just state in your will that the ivy must be removed before anyone gets their inheritance. 

I want an indoor herb garden for Christmas--but the plants are out of season (rosemary, basil, bay) or an olive tree in a fancy terra cotta pot. Where do we get these (no, I don't want Williams-Sonoma). Secondly, the big evergreens outside our front door are gone-cut off at ground level. I'd love to plant bulbs--naturalized to bloom over the spring and summer. Is the progression narcissus, daffodils, tulips, day lilies? Are there autumn blooming bulbs?

These are all somewhat hardy plants that actually do very poorly in most home environments. Buy and enjoy them for a few weeks, but don't expect them to last. I see rosemary topiaries in supermarkets that are already clearly suffering from environments that are too warm and dark. There are autumn flowering crocus and colchicums. Lycoris blooms in later summer. 

I am very glad you wrote about the evils of English Ivy ( now thought to be Irish ivy ) but why encourage anyone to buy it ? As you said , it can make. berries and spread - an alterntiative might be Loncera sempervirens- our native honeysuckle -this may have to be attached and needs sun but ,feeds hummingbirds . There may be other plants as well . Thanks!

Thank you. Another native vine is the American wisteria, Wisteria frutescens. That's handsome and better behaved than the Asian species. 

I had success sprinkling (lots of) hot pepper flakes on each bulb when I planted it (wonderful suggestion from my dear mother-in-law)

Thank you for that.

When I bought my house 25 years ago, the previous owners had planted English ivy on the ground in front of the kitchen. It was growing into the crawl space under the house. It took me several years of repeatedly ripping it out to get rid of it.

I had a lot in my garden at first, I found it quite easy to rip out. A mattock is a great tool to get wayward roots. 

Mr. Higgins, When and how should I plant virginia bluebells? Separately, how do I not kill my mother's peony when attempting to divide it? Thank you

Probably with a slender trowel. Virginia bluebells, Mertensia, has fleshy roots that should be dug and separated, if that is needed, before the leaves fully retreat in late spring. The peony is best dug and replanted, however, in late summer. 

Hi Adrian - We have a home that is set on a 5+ foot rise. The sloped area probably covers a linear 90 feet. Currently the slope is covered with a type of woody vine that requires weed wacking every few weeks. We were thinking of replacing it with something that requires less maintenance. One possibility seems to be the foot-tall, green plants with purple berries on short stalks that one sees in DC in yards and tree boxes. (I don't know the name however.) DO you have any suggestions? Thanks.

I don't know what you're describing but if you have a ground cover on a slope you want to replace, it is best to kill it with an herbicide, remove the top growth if wanted, and then plant through the old planting. Though it's dead, the roots are holding the soil in place while the new plants grow and knit together. 

Hi Adrian, This year I brought my containerized lemon tree into the garage for the winter instead of the house and so far it's doing fine. I've read that i should keep the soil moist during the time it's in the garage. Is that the proper treatment?

Alas, this has to be the last. You should water occasionally but not as much as if it's in active growth. The citrus will still need some light through the winter, and will have to be kept above freezing to avoid winterkill. It's possible that in your setting it may drop many of its leaves, but should bounce back in the spring. Thanks for tuning in and see you here next time. 

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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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