Adrian Higgins gave advice on tending your garden after Sandy

Nov 01, 2012

Has your yard and garden taken a beating from Hurricane Sandy? Adrian Higgins is on hand to offer advice on what to do -- and what not to do -- in the wake of the storm.

What is the best way to get grass to grow under oak or maple trees?

Please don't be shy: Send me your questions about the battering your garden has taken with Sandy, or anything else on your mind about what should be a very busy and exciting time of year for the gardener.

Oaks and maples. It is quite easy to grow grass under oaks, it is quite difficult to grow grass under maples. Maples have more surface roots and their canopy is much denser, robbing turf of the light is needs. The worst maples for grass are silver and Norway maples the former for surface roots, the latter for surface roots and dense canopy. If you can, I would underplant maples with a ground cover that can take dry shade, such things as hellebores and heucheras. If the surface rooting is pronounced enough, I wouldn't try to grow anything close to the trunk, and don't keep piling up the mulch: the root's trees will grow into it. 

I've got wild violets slowly spreading throughout my yard. Any suggestions for getting rid of them? I'm open to anything.

Me too. If you don't know about wild violets, you haven't lived. They form rhizomatous clumps and they are devils to get rid of because you have to extract the whole plant. You could use an herbicide such as triclopyr, but this will kill pretty much everything else around it. If you have half a lawn consumed by violets, this may be tempting. In garden beds, I just dig them out -- a highly effective tool for this is the mattock. Get the blade underneath and out they come. Violets are symptomatic of wet soil, so the more you can improve drainage, the less the problem.

We have moss taking over the grass in our front yard. How can we get rid of it? It's a very shady yard, and we would like to have grass again, if possible. Can we just reseed, or do we need to start over?

Again, moss is an indication of moisture but also shade and soil compaction. You should fix those conditions before sowing grass. We are right at the end of cool season grass sowing season, so you'll have to hustle on this. 

I have potted mums that are on their last legs. I would like to transplant them so they can come back next year. What is the best time to do that, and what kind of soil and light do they need? Thanks!

They do well in ordinary soil and can take sun or partial shade, probably preferring the latter more. I would remove the fading flowers but keep the stems (they provide winter protection). Once you see new growth next spring, you can remove the old, dead growth. Remember to pinch back the stems at least twice before July (as is done in the greenhouse) so that you have a plant that will stay bushy. It will probably bloom later next year than this because the blooming time is manipulated in the grower's greenhouse. Personally, I would use my valuable real estate for something of more longstanding beauty, maybe a daphne shrub. 

My garden did not take much of a beating, although I don't have much of a garden right now. I am planning to build up a couple of raised-beds and put my garlic and fall-planted shallots in (first time I am trying the latter), so my big concern is, with all that rain we had, can I get away with planting this weekend if I have time or should I wait another week?

Very timely question. The one concern with wet soil is that if you stand on it, you will squeeze the life out of it. This is why I always recommend having separate paths in the vegetable garden. I would take a shovel or fork to a bed before working it this weekend to see how wet it is. If it's squishy, I would leave it a few more days. 

I planted my spring bulbs, and then came Sandy. Will they be okay in the ground, or will the waterlogged soil hurt them?

As long as the ground doesn't have standing water, they should be alright. The difficulty is that they don't like wet conditions or freezing until the roots have begun to grow. 

We have a Japanese maple tree that is very close to an outside stairwell in our house. We had trouble during Sandy keeping the leaves from the maple from clogging the drain at the bottom of the stairwell. I really like the tree and don't want to lose it. Is it possible to move a tree to a new location without doing permanent harm to it? (FWIW, I don't know how old the tree is, but it was there 3 years ago when we bought the house)

It's possible to move a Japanese maple if you preserve enough of the rootball. When dug, the ball should be wide rather than deep. The diameter of the rootball depends on the size of the tree. I assume this is a slow growing weeping Japanese maple. Now would be a good time to move it. If it is a fine old specimen, however, I would root prune it now and then move it in a year. This entails taking a sharp shovel and making a dotted line circle with a radius (not diameter) of probably 12 inches from the trunk. By thus severing half the roots, new roots will grow at the edge of the circle, which can be preserved when the tree is lifted next fall. 

We have some new plantings that are supposed to get an inch of water per week. The yard got at least 4 inches thanks to Sandy. I know we shouldn't wait four weeks to water. Would you give some guidance, please?

Nothing is going to need watering at the moment. An inch a week is a lot at this time of year.  Is this for a newly sown lawn? New plantings such as shrubs and perennials need watering to get established, but they should be well soaked and then left alone, or they will drown. 

I don't understand why people want to get rid of moss. I'd like to know how to spread it. It's pretty and doesn't need to be mowed.

I agree, though I will say that creating a beautiful moss garden in Washington is much tougher than in northern states or climes.

Our six-year-old rain garden isn't draining. The guy who cuts our lawn and does other big jobs for us says it needs to be re-dug, and dug deeper. Do rain gardens silt up? Ours has cattails growing in it -- we can't keep them out and it's futile to try -- does this have anything to do with the rain garden not draining, and how often do rain gardens need major maintenance? We kind of thought we were done when we had it put in.

I suspect that rain gardens, like roof gardens, are not capable of sustaining themselves forever, in spite of all the hype. They silt up, they get weeds. The idea of a rain garden is that you excavate a bed, backfill it with sand, gravel and soil and allow it to capture rainwater for a while before it seeps out. You use floodplain shrubs and perennials to decorate it. Your fellow may be right, and yours needs re-doing to a greater depth. 

We have some large old maples that will probably die soon. Will the shallow root system that makes it impossible to grow anything under them be a problem when they are removed? Does it matter whether or not we have the stumps ground down? We want to replace them with trees but want trees that grass or plants will grow under.

Maples tend not to resprout from stumps, so the only impediment to fresh planting is the physical barrier of the roots, this may be enough, though, to warrant the use of a stump grinder. 

what's the best way to grow/replace basil, mint and chives that were on my balcony, and, since being inside, have withered away?

None of those herbs will grow happily indoors unless you have a bright, cool conservatory. I suppose you could keep the supermarket packs of basil going on a bright windowsill. Chives and mint, which like it cool, could be kept going outdoors under hooped row covers, but I don't know that you want to go to that trouble, even if you have the real estate . 

Thanks for your response...we installed shrubs and trees, so will pay attention to what you said about too much watering. But could you elaborate on when to think about watering again? Should it be based on how dry the ground is in a week or so?

You should give them a good watering when planted, but then not water again until the top inch or so has dried out. Keeping the soil wet is the quickest way to kill a newly planted tree or shrub. A saucer of mulch should retain moisture for a long while at this time of year. Keep mulch away from trunks. 

Hi Adrian - Is there a mobile phone app for plants? I'd like to take a picture of a leaf or flower and then have the app tell me what it is and about what growing conditions are suitable for the plant.

There probably is, but no app is going to know your growing zone, soil or light conditions, microclimate or give you a sense of what an abelia you plant today will look like in five or ten years.  Perhaps one day, a super app will do all that, and take all the joy out of gardening in the process. Go Analog!

Not Sandy related, but I had a large, very old tree removed from my front yard, but have not yet had the roots removed, or ground. Am I able to plant another tree in that spot? If yes, how soon can I plant? And do I need to do anything with the roots of the old tree?

As long as the plant didn't die from a fungal or blight disease, or uncorrected waterlogging, you should be all right to plant right away, if you can negotiate the physical barrier of the stump.  

My backyad is nothing but TREEs... Lots and lots of trees. We get so much shade that all we have is mud/dirt. I'd like to make the yard usable but we have a lot of exposed roots. I really don't want to cut down trees but is there a way to get the grass to grow or what do you recommend for grass seed for heavily shaded areas?

You don't say what sort of trees, some are better than others. If you have so many that the yard is unusable, I would thin out the stand (also for the health of the trees). Fine fescue grasses can take a degree of shade but no grass is going to flourish is deep shade. I think I might consider removing some of the trees, establish a path through your woods, and plant some lovely ground covers. Check out Fern Valley or the Asian collections at the National Arboretum. 

Do you have any suggestions on how to prune a Bradford pear. We have lost three over the course of the last 10 years but want to do what we can to preserve our one remaining tree. Some neighbors have given theirs a severe cutting back -- leaving mainly the trunk. They grow back but for a year or more they are ugly. Is there a less aggressive way to prune such a tree that will help preserve it?

Bradford pears are inherently weak because the branches converge at single points along the trunk. The only way to fix this is when you're buying a young tree. You can select one with a better architecture and, when the main branches are young, you can remove some to further avoid this problem. This wonder tree is now wholly discredited in horticulture. Apart from its tendency to break up, its seeds are causing it to invade natural areas. 

I noticed during the storm that my sump pump seemed to be recycling the same water over and over--when it would kick on, a big puddle would form in the garden where the exit pipe is. Then the water would slowly dissipate until there was no puddle, and just about then the sump pump would kick on again. It cycled on every few minutes until we lost power. Power was out 2 1/2 hours, and the water in the bucket got to just about the level where it should have cycled on, but no higher. Power back on, pump resumed cycling on every five minutes or so. Next morning I went out and dug a few trenches into the lawn to allow the water to drain better, AND I collected the water from one on cycle in a bucket and disposed of it elsewhere in the yard--no more on cycles. Clearly I need to do something. But where/with whom do I start?

You need to make sure that the water that is pumped out is taken far enough away from the foundation to leave the area. This may entail adding drainpipes.

By the personal pet peeve, which no doubt will increase my blood pressure yet further, is that PEPCO/Montgomery County/DC et al do not take responsibility for grinding out the stumps of all the trees that they cut down during regular tree trimming and weather events like the derecho and Sandy. Within about 2 blocks of my house in MoCo for example there are at least a half-dozen stumps that need to come out. I would submit that we gardeners as a group, with you serving as the Speaker From The Bully Pulpit, get on this as a key issue, because these spaces need to be re-utilized appropriately, and the Asplundhs and PEPCOs of the world need to take responsibility for cleaning these up!

Absolutely, and how can you plant a new tree in the confines of a tree box unless the old stump has been ground out? 

There is such an app; it's called on-line gardening forums. Post the photo, add your location and zone, and people will instantly identify it for you. Trust me on this.

Sorry, but plant ID from photos is iffy at best, and a lilac that grows in Maine will not perform the same as a lilac in Maryland. 

In a storm last year we lost three Bradford pear trees. We paid a tree company to ground the stumps. We were told by a nursery that we could not replant trees in the old holes because they would eventually collapse more and that the roots from the old trees would be rotting in the ground. Other nurseries have disagreed. Would you replace a Bradford pear with a ground up stump using a different type of tree in the same spot? Thanks very much.

Stump grindings will decay, and the material shrink, but as long as the new tree rootball sits on subsoil and the roots remain covered, the presence of the grindings shouldn't make a difference.  

We just planted two new trees three weeks ago - a river birch and a red maple. The landscaper instructed us to water both daily with a few inches of water for 2 weeks, then reduce the water for the next two weeks. I set up a timer on hoses to sprinkle water on the root ball area. From the advice you gave earlier in the chat, it sounds like this is way too much water. Or is it necessary?

We have to leave now, but while the birch is a lowland tree that can tolerate moist soil, no, no new trees should be watered daily. This is a death sentence. Soak them when planted and then give them another soak in a month, and let them sit out the winter.  See you next time.

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Adrian Higgins
Adrian Higgins is The Washington Post's gardening columnist. Read his recent story on tulips and follow him on Twitter.
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