Adrian Higgins gave advice on tending your garden in the fall

Nov 15, 2012

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

Hi Adrian - love when you chat with us! This fall, I have a huge problem with what I think are voles. Tunnels everywhere in my yard and garden. I've always had some, but this year is really bad. My cat helps a little (yuck!) but not enough. I've heard that they are attracted to grubs, but I don't seem to have many of them. I hesitate to use poison - any suggestions?

Hello everyone, and thank you for joining me for our late fall chat. Though the winter is upon us, the last displays of the fall leaf colors are just stupendous this year. I am particularly thinking of dawn redwoods (orange copper needles before they drop) and the ginkgos, which are stunning this year.  Do take some time from your busy days to look at some ginkgo trees. Voles can be a real problem. They are the bane of hosta and daylily growers. I'm not a fan of poisoning them, and when I had a cat, she took care of them.  My colleague Barbara Damrosch has devised a vole trap that seems to work well, it's basically a box with mouse traps in it. Here's what she wrote recently: http://www.washingtonpost.com/lifestyle/home/catching-winter-critters/2012/10/30/438ae924-1c7e-11e2-8817-41b9a7aaabc7_story.html

My yard contains a majority of oak trees. I have not been successful in finding a quicker way to break their leaves down for composting, mulching purposes. We have tried large bins with lime, running them through a mulching machine. Even the smaller leaf "bits" take a long time to decompose. Suggestions?

Oak leaves are the best for compost, they don't mat down like other leaves and yes, the tannins do resist decomposition. Continue to shred them but hold back on the lime, this impedes microbiotic activity. Mix them with green stuff like veggie wastes and lawn clippings, and make sure the pile is moist. An interesting stat: Every time you turn a compost pile, the duration for finished compost is halved. 

I have had a lilac (lovingly passed from my long gone farmer-uncle's yard and a DOUBLE bloomer normally) since 2004. It is hardy and used to produce wonderful blooms. For the last two years, though, it has not produced flowers. I've done a lot of research and determined that I am cutting back at the proper time of year so I don't believe it's that. I suspected it could be that we have had a lawn service for the last two years and that they could perhaps have something in their treatments that are hindering the flower from blooming. Of course, they say no to that, but I could understand that happening based on the timing of when the flowers stopped blooming. At any rate, is there anything I can do in the fall to prepare the plant (ie - change the soil makeup?) I read something about putting crushed leaves around the base to increase the nitrogen?

Lawn fertilizer tends to be heavy on nitrogen, which is something the lilacs don't want, it will impede flowering. They do better with phosphates and potassium feeds. Another way to revive them is to remove the oldest canes, which I would do in May after next season's blooming. Encourage some of the younger canes to develop into flowering wood. I would also enlarge the bed in the lilac root zone to keep the lawn service away from it. 

I am moving into an apartment where I will have a patch of ground for planting whatever I want, approx. 6' x 40', northern exposure, some of it under a maple tree. Is there anything I can do over winter to improve the soil for spring planting? Thank you!

This is a generous space, in order to avoid the tunnel effect of so long and narrow a yard, I would plant perennials and annuals that will divide up the area and not reveal all at once. Banana trees might be a lot of fun (the hardy Basjoo or the Abyssinian Red). If you build up the soil in the root zone of the maple, the maple roots will grow into it, it will be a futile exercise. Better to grow things in pots under the maple, but make them large pots and be ambitious with large leafed plants such as cannas or colocasias. 

It's freezing out there today. Is it too late in the year to plant shrubs or small trees (like red maples)?

No, the soil is still relatively warm and you will get some root growth before the freezes. You will need to check newly planted trees etc. in late winter to see if the freeze thaw cycle has exposed roots, which would be bad for the plants come spring.  

I have many trees on my property, so I exclusively mulch leaves with my mower because raking and bagging would take forever. How much actual "nutrition" is in these millions of oak/maple/beech tree leaves? Is this nutrition actually good for grass? Yes, I'm too lazy to rake but I would hope that I am doing some good in the process.

This is the best thing you can do for your grass (along with core aeration). The shredded leaves will be conspicuous for a while, but the worms will take care of them over the winter. They will feed all the beneficial microbes in the soil, and the grass will love it. Pains me to see folks pile leaves up on the street.

I want to grow something edible in the window at my office. What would be a non-intrusive plant for a sunny window? Garlic? Herbs?

I think I might go with a scented geranium (pelargonium) or perhaps some chives. Most hardy herbs aren't going to be happy in the dry heat of an office. Do others have some suggestions? 

Is it still OK to fertilize my lawn?

Yes, but use a formulation for fall, which should be lower in nitrogen.

Is now about the right time plant daffodil bulbs?

It's not too late to plant daffodil bulbs, though they should go in before the tulips, and are probably best planted in October.  You may get later than normal blooming next year, but in subsequent years the bulb will return to its natural bloom time.

I have one of these trees and it seems that the outside branches are growing a lot faster than the internal branches. Some of the branches, probably due to my pruning, have starburst ends. What can be done to right this? Tree is about 5 ft. in height.

It's important to prune a young tree correctly to anticipate its future growth and habit. If you prune excessively you will get suckering, as you will if you simply truncate a branch. It it is congested, it is better to remove entire branches, starting with those that are growing inward or rubbing. Be conservative.

Husband runs the mower over the lawn one final time after the leaves have fallen, dumping the bagfuls of mixed chopped materials onto the compost pile. Voila! Two chores completed at the same time, three if you count filling the compost.

Four if you count husband out from under your feet. :)

This is my first year planting bulbs. Our house came with some beds already planted, but there was definitely more space for early flowering bulbs (eventually it gets too shady). I acquired a range of early spring bulbs and planted them according to their instructions. Within hours the squirrels had dug them up. Maybe I will be lucky and some of them were re-buried and could still grow. My question is how do other people avoid this problem? Like I said, we have some beds that managed to keep their bulbs from the past. The neighbors have spring flowers. What is the secret?

Squirrels are drawn to the sight and smell of freshly dug earth, so it helps to put mulch or leafmold over the ground to confuse them. The most effective way to thwart them is to bury the bulbs deeply, seven or eight inches or more. This is hard if you don't have a good digging tool and with heavy clay soil. I use a long handled bulb planter, which engages all the limbs. If my soil is really bad, I will actually hack at it with a mattock. The other solution is to place netting over the recently planted bulbs, but this is a pain and you have to remember to lift it before the bulbs grow. 

We have a couple of large old Norway maples, whose large leaves not only take forever to fall, but they seem more leathery than those of our red maples. They take forever to dry up enough to mulch up for the garden, which extends our fall cleanup past the time that the county will pick up yard waste. If we bagged the Norway leaves and let them sit out all winter, would they decompose enough to m ix into the compost, or just sit there being a nuisance?

The danger is that they will decompose anaerobically, and produce nasty acids. My strong advice would be to consider removing this tree, which I find depressingly dense in canopy and thick of root. Think what you could grow in its absence.

We have a good neighbor who used to bag his leaves and grass clippings for trash collection. It bothered him to have to do all that extra bagging work, as well as the expense of the bags. So, we set up a compost bin just inside our shared property line, and now he can lean over and dumps all his leaves and clippings into it. Then each summer we share a bit of our vegetable garden bounty and berries with him, as repayment. Win-win!

Fantastic. A shared compost bin, absolutely fabulous.

I have my first NoVa yard, which is a small, open rectangle with partial sun exposure. It is a blank slate at this point. My intention is to have a small raised vegetable bed in the sunniest spot in the spring, but what would be some good foundation plants that won't get too big to get started on landscaping?

It's good to start small, nothing worse than to have a vegetable garden that is too big and overwhelms the beginner.  But in planting the larger landscape I would make sure that you are able to expand the vegetable garden as your knowledge and interest grows. So, avoid big or dense trees or large shrubs that will invade your light and soil. (No Norway maples!). Boxwood are great companions to the veggie garden, and I love the idea of planting pomegranates, which are now pretty reliably hardy here given our "climate change". 

I'd like to put a plant or two (maybe herbs?) on my windowsill to keep me going through the winter. Any suggestions?

My efforts to get other readers to suggest herbs has fallen on deaf ears. (Hint, folks). It might be fun to try a little lemon thyme, if your window is bright enough. Cilantro is fun too. One point about indoor plants, especially herbs: When watering, take the pot to the sink and give the roots a good drink, but then let them drain before replacing them. Don't stick them in trays and water them in situ. They will get waterlogged and croak.

You're welcome to come to my house and pick up the leaves for a compost pile. Let me know when you'd like to stop by...please bring a tractor trailer to accommodate all of the leaves.

If you have that many, you might want to invest in a heavy duty shredder. You will never have to buy mulch or soil amendments again. 

Unfortunately we are stuck with our big old Norways; they are our only shade in the back yard (and divide us from the too-close neighbors). But when they die, which they probably will in the next ten years, what should we plant, and how much trouble should we go to to get the roots out before planting new trees?

OK. But wouldn't it be better to fix it now rather than in 10 years or so? You can get pretty good leaf canopy in that time from a new tree. If you need the shade I would consider something like a cultivar of the native red maple, the littleleaf linden or a willow oak.  You should get the main stumps ground out, but don't worry about the other surface roots, which will decay and disappear.

This happened to me the first time I planted bulbs. I generously sprinkled red pepper flakes over the soil and that seemed to deter them.

Yes, these repellents will confuse the squirrels, and may do the trick. I'd still bury them as deeply as I can (the bulbs, not the squirrels). 

We're finally buying a townhouse this month and will for the first time have a (small) yard. Come spring, I assume we'll have some mowing to do, but it's a small area -- maybe 10 ft by 7 ft. Are there mini push mowers? Do you have a favorite? This is our first time with any green space, so we're a little clueless.

A push mower would be fine for such a small lawn, if you could find one that would do the job. Unless mower designers have got with the program of late, the push mowers cannot be set high enough to give you a three inch cut, which is what you need in Washington. Anything lower than that will stress cool season grasses in our hot climate. I would consider planting a groundcover instead. I was bowled over the other day by the sight of a mass planting of green (not the ugly black) mondo grass set amid large stepping stones. 

Adrian, Can I prune some large branches from my Oak and Maple? both are 8-10 in in diameter. I am looking to prune some major lower branches as the trees are more than half leafy branches.

I would advise against it. Those are large boughs and I would be concerned on a number of levels. First, you might imbalance and dismember the trees (hard to know without looking at them). Second, these are heavy limbs and need to be removed with skill, particularly if they are elevated. I would get a pro to do the job, i.e. a certified arborist, if it needs doing. 

What's the best time to get trees assessed (whether they should be taken down, etc.)? Any recommendations for that service?

It takes more skill to discern a tree's health after leaf drop, but it's also easier then to see the architecture of the branches. So now is a good time. I don't make recommendations, though I would urge you to get a number of estimates. Tree work is a dark art in this town, and I've heard horror stories of price gounging. 

Hi Adrian - I have an indoor plant questions, not sure if it's up your alley. I've noticed that a lot of my indoor plants have mold on top top of the soil. These are mostly succulents and I use the special succulent mix potting soil for them. The plants themselves seem to be doing ok. Is this a concern? Should I repot? or add something to the soil?

Succulent mixes tend to be free draining, so the presence of mold is a bit of a worry. I wouldn't repot now, indoor plants  are better repotted in the late winter but I would get tiny grit and mulch the plants with it, perhaps after removing half an inch or so of the moldy top stuff. 

I like to cook, so every autumn I move a window box with parsley, oregano and sage from the patio into the kitchen. Very handy to toss into a stew or sauce. Unfortunately my favorite herb, basil, will not survive indoors.

Useful to know, thank you. I should write about this. Thank you for all your questions today. Let's meet here again in late winter when the sap is rising. 

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Adrian Higgins
Adrian Higgins is The Washington Post's gardening columnist. Read his recent story on Lady Bird's legacy of beautification and follow him on Twitter.
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