Adrian Higgins gave advice on tending your garden in the fall

Oct 17, 2013

Washington Post gardening columnist Adrian Higgins took questions on how to improve your garden in the fall..

Hi Adrian, so glad you're here! Is it OK this time of year to move roses and other shrubs to a new location? (I live in central PA). Thanks!

Thank you. My story today was about the dark art of moving existing trees and shrubs. You will note in it, perhaps, the lack of reference to roses because in my experience roses that are more than a couple of seasons in the ground, are extremely hard to move, the roots run deep. I would try it in February before bud break, after a regular winter pruning. Sounder, though, to plant a fresh rose. I have found shrubs, ramblers and climbers are well established and flowering by their third season. 

I am always wondering at what point in the fall growing season is the time to cut back the leftover stems and leaves on perennial flowers like peonies, daylillies, garden flox and other traditional plantings around my 1850 farmhouse. Do I wait for them to really turn brown and die back or should/could they be trimmed earlier?

The short answer is, when you get around to it. There are some reasons to keep the dead top growth of perennials, it can provide seed sustenance for birds and other wildlife, it can look great when iced -- rimed is the technical term -- with dewey frosts in November, and leaving the old stems affords a measure of freeze protection for marginally hardy things such as agastaches and penstemons. I would remove the foliage certainly of peonies, lilies  and daylilies. 

When/how can I transplant my dahlias to another location in the garden? Should I wait until all the green has died back and the plant is dormant?

Wait until the first good freeze has killed the top growth, this will ready the tuber for winter storage in a ventilated box of slightly damp moss or sand. I would divide when they begin to sprout in April. 

Seriously, is there any value to cover crops? They sure don't suppress weeds, they 'may' add some green fertilizer, but seriously - what value?

I think they can do a great deal to suppress winter weeds, which are germinating now by the way. Winter rye, red clover and vetch should be sown now (or better, a month ago). Cut them and turn them into the soil in early spring. 

My lima bean vines grew great, made great pods, but NO beans in the pods... Do you have any ideas as to why?? Ack! I love limas!

It sounds like they were not pollinated. Make sure you do everything you can to attract bees and don't use pyrethroid or imidacloprid pesticides, to name a couple of real problem poisons for bees.  

I have a Ywe Bush that I planted in May but it didn't survive the summer. Is fall the best time to replace the bush? If so, how often and how much water should I give it? Thanks for all your great advise!

I'm assuming yew. Now is a good time to plant, no later than mid November (that's true for all evergreen shrubs, I'd say). Yew likes a little moisture to get established but hates wet soil. Most yews are killed by people overwatering them, in my view. 

Hello! I recently tore out the front lawn and I am slowly constructing a garden. In the western (hot sun!) corner I placed 3 chino viburnums for screening. I'd like to put a large shrub inside that corner, visible from the house, and edge it with some tough perennials like paprika yarrow. I'd like a cascading form, rather than upright, to contrast the viburnums. Ideas so far include Chinese Abelia, snow panda loropetalum, bridal wreath spirea, tardiva hydrangea or dwarf crape myrtles (although these seem fairly upright in form), some kind of rose (which I'm not convinced I can properly care for) or some kind of hybrid abelia (twist of lime comes to mind although it is rather small). My 1960s tri-color brick house is begging me to stay in a muted color pallet: no fuschias, no bright yellow leaves. Oh, and deer sometimes stroll up from Rock Creek Park. Many thanks for your feedback!

First, you should know that the Chino, popular in the South, is a big evergreen shrub. I have one that is 20 feet tall. So give them room or pick something else. A dark evergreen screen cries out for something flowering or fruiting on naked stems, I'm thinking a witchhazel or a stand of Sparkleberry hollies. Loropetalum would be nice.

the bed in the front of my home got overrun by weeds and vines. I paid someone to clean it out and it was perfect for about 2 weeks. Now it is right back where it started. What do I have to do to keep the intruders out of the bed?

Er, weed. If you're not weeding on a weekly basis, they will win. Mulch will help, but you have to weed.

We usually have good luck with basil and are able to keep it into the early winter. But this year, our basil didn't do very well. Is it too late to get some basil plants and perhaps keep them in pots that we can bring inside when the frost hits?

This is the end of basil season. Basil turns bitter once nighttime temperatures drop into the low 50s. Basil is also afflicted by a new disease called downy mildew (new to basil) and yours may have been afflicted by that. I wouldn't try to keep it as a houseplant. If you have loads of basil now, the course is to harvest it for pesto (which can be stored in the freezer). 

I want to start a little herb garden on my second-floor terrace. I've never successfully kept any plants before--when should I start planting the seeds? Do I need a special kind of soil?

Spring is the preferred time to start, but you could now grow parsley and violas (edible flowers) in pots, which will last until the New Year. Other stuff will either be beaten down by the frost or won't be hardened off enough to survive a winter. Any pot must be free draining and frost proof. 

So, can I safely cut back the dead/dying foliage on lilies (including hostas), yarrow,lavender and other perenniels now? It's all so untidy and ugly.

Everything except lavender, which can be trimmed once new growth is evident in spring and then not back to bare wood, and again after blooming. 

I keep thinking the next time I mow my lawn will be the last time for this year. What height should I set the mower on for the final cutting, whenever it happens?

Hold your horses. Now that it has rained, you might want to apply fertilizer. This will induce growth through November. Moreover, the best way to get rid of fallen leaves is to mow them into shreds where they lie. They will soon break down and feed the soil.

Racoons have completely destroy my front yard digging up grubs. Is there anything I can do now to kill the grubs or do I have to wait until next May/June to lay down something to get rid of them? It looks like a car has driven through my yard with all the grass torn up. I was thinking of purchasing a scarecrow sprinkler but not sure how effective it would be.

If you have excessive numbers of grubs, you should address that, if only for the sake of your lawn. Unforunately, one of the most effective grub killers is the aforementioned imidacloprid -- keep it away from flowering plants that might drawn bees. Milky spore is an organic control of grubs, though not terribly effective, I think. What have others folks done about this?

In the Washington Post Garden Book, you mention Nandina as one of the "best' shrubs for this region, but many online guides describe the plant as invasive. Do you still consider it suitable for the DC area?

Nandina is more of a problem in the Deep South. I have to say, it's an incredibly useful and attractive ornamental that can take soil and light conditions that others cannot. 

Just a reminder that an easy way to manage fallen leaves in the autumn is to run the lawn mower with the bagging attachment, which "kills two birds with one stone": not only does it cut the lawn but also gathers and chops most of the leaves, and the mixture can then be used for mulch or compost.

That is true, though you have to keep stopping to empty the bag. Just mulch mowing is effective as long as the piles of leaves are not ridiculously high (after they have been blown, for example). It might help to rake them into thin layers before mowing. 

I have tall and pygmy Nadinas (because the deer do seem to not eat them!). When is the best time for pruning and how severe should I go? Any special instructions?

Prune them in late winter or early spring, after freeze or salt damage is evident and before the new spring growth gets going. I have a dwarf nandina that is more difficult to prune, it leaves gaping holes in the mound that takes a year to fill in, though it will. 

I've cut back my peonies but wonder about my large false indigo. Let it go over the winter, and cut it back in the spring like chrysanthemums, or do it now?

If it is ugly, I'd do it now. If you clean up in late winter, you run the risk of damaging the emerging growth. 

We are digging up the euonymus evergreen and photinia hedge that the deer are browsing all the leaves off, and have ordered Festive Red hollies to take their place. How much compost or mulched-up leaves should go into the holes with the hollies? I know they like acid soils but our leaves are maple, not oak.

There is a school of thought that tree and shrub holes should not be amended with organically rich material, but with the native soil, to prevent a container-growing effect where the new root growth stops at the wall of the hole. I sometimes add some pine needles and some sand to the native clay, to give the roots some encouragement. I love to water new trees and shrubs with an emulsion of fish fertilizer. 

I've given my 3 chindos 8-10 feet to grow in width. Not enough?

Yes, that's enough, just. But they will get tall.

I have planted some winter vegetables - some in a cold frame, some not - but I'm not sure how much to water them once frosts start to hit.

You don't say what they are, but I'm supposing some winter greens such as lettuce, kale, arugula? Water is not as critical in the fall as in the spring, but they shouldn't dry out. Veggies need enriched soil which by its nature retains moisture. Plants in cold frames can get very dry and must be watched.

I've kept mine thriving in a 4th floor condo using a grow lamp. It's been out of the sunny window for a month now and still going strong.

In full sun, I would consider some abelias or dwarf, read, dwarf crape myrtles. In shade, I would consider a prostrate yew, boxwood or some hydrangeas. 

Hi Adrian, I loved your article today on moving trees. We have a small (10 foot) dogwood in our yard that the kids like to climb on, however we need to widen our driveway. So we either have to move the dogwood or chop it down. It has been there about 30 years however it has never been what I would consider a healthy tree. It gets full sun in our front yard which has southern exposure. Would you have any thoughts on moving this tree? I know I didn't give you much to go on. thanks, -craig

Dogwoods are not the most amenable to moving and if it has been there for 30 years it is time to plant afresh inthe new location, I'd say. 

I hated nandina until I read this pruning advice--cut in threes. Leave a third, cut a third to the ground, and cut a third to various heights. Now my shrubs are bushy and gorgeous.

Great advice, thank you. 

Planted garlic cloves about 1 1/2 weeks ago following the planting instructions from Burpee with the anticipation of harvesting next spring/early summer. Shoots have already appeared--I have raised beds and the area receives sun all day. How do I protect these plants during the winter if there is snow or ice? Thanks.

The cloves should be planted nose up with the tips about an inch or two below the soil line. Wispy growth is good -- just leave it, it will know when to stop growing when it gets cold. Most of the fall stuff is going on under the soil, with root growth. Now is also a great time to plant cloves of shallots. 

Do you have any favorite Web sites or other resources for learning about edible landscaping and keeping as native as possible? I'm in Arlington if that helps.

I don't, perhaps others do. Most edible plants are not native. If you want to ponder the attractive use of edibles, there is no better source than the book Edible Landscaping by Rosalind Creasy. 

We have to move from a community garden. How can I take by raspberry, blackberry and blueberry bushes? Can I move my Elderberry?

You should be able to lift the elderberry if you are careful to keep a decent rootball. I would also take the blueberry and the blackberry. Raspberry canes don't age well -- they get virused -- I would start afresh with clean stock. I have to run away now, but hope to have another chat before the fall planting season wisps away. Thank you for joining me today. 

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Adrian Higgins
Adrian Higgins is The Washington Post's gardening columnist. Read his recent story on how to move a prized tree and follow him on Twitter.
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