Adrian Higgins gave advice on tending your garden in the summer

Jun 13, 2013

Washington Post gardening columnist Adrian Higgins took questions on how to improve your garden in the late spring and early summer..

Any thoughts about Hugelkultur used in conjunction with raised beds? The thought occurs to me to use the quite-large number of branches I have trimmed off some oaks/maples on my lot, within some raised beds I need to build out, and maybe give a leg up to my future planned asparagus bed. I think it would help provide some additional drainage. Yeah I realize it will be some back-breaking work to dig out the dirt, but aside from just amending with all the leaf/grass compost I have, some other way of not only improving drainage but also increasing nutrients in the ground long-term is needed. The light bulb on this sort of went off with the last issue of Fine Gardening magazine that talks about the technique.

I didn't know what this was until I Googled it. This involves digging pits, putting in logs and then growing plants in mounds -- garths? (a word we don't use much anymore). Seems like an awful lot of work for results you could get with simple raised beds and soil amendment. Welcome everyone, by the way.

Read today's Local Living story on geraniums here.

I've got violets spreading wildly across my yard. What are the options to get rid of them or is hand digging best? Is there anyway to stop them from spreading any further?

I use a Japanese weeding knife or even a mattock to scoop them out of the soil. You have to get the little bulbets to stop them coming back. They are invasive and a real pain. I don't use herbicides, though I suspect there are some available for this viola. 

I planted a vegetable garden this year (first time ever). My husband built me two raised beds and we got garden soil from the local garden center. A few weeks after I transplanted my seedlings, I noticed that they are stunted and yellow. Hubby got me a soil test kit and I couldn't believe how deficient the soil was in N and just sufficient in P and K. I supplemented with blood meal and fertilizer in a bag, specific for veggies two weeks ago. The plants seem to be recovering but I wonder if I should expect any kind of harvest this year or is it all a failed exercise? Do plants recover from a bad start?

Nitrogen is fugitive so you have to give your plants a feed from time to time (not too much, and fruiting veggies like tomatoes and cucumbers won't like nitrogen when they are setting fruit, preferring phosphates at that point. I find that if the soil is rich enough with organic matter, the need to fertilize is much diminished. Keep at it, and keep adding (if you can) rotted compost as a top dressing. The soil microbes will make hay, so to speak. 

I am growing arugula this year in containers on my balcony in addition to some other veggies and herbs. My issue is that there is something eating my arugula - and only the arugula! The internet leads me to believe the problem may be flea beetles and most websites say that they are not harmful. They will just leave small holes in your arugula which is better than using an insecticide. I wouldn't mind eating arugula with holes, but the critters have left nothing! They have eaten the leaves down to the stems! Any suggestions? I don't want to use chemicals and I don't think netting will help.

The main pest of arugula is the flea beetle, a tiny black insect that makes holes in the foliage. We are at the end of the first arugula season here, it simply bolts in this heat. Sow seeds again in mid August for a fall crop, when the flea beetles seem to have gone on vacation. 

The cicadas have done significant damage to my small cherry tree. Most of the branches are broken about a 12 - 18" from the tip. Can I remove the broken branches (before they fall on their own) and if so should I cut right below the break or further down the branch? Thanks.

Too bad. I would wait to see if the branch cutting has, indeed, killed a branch before taking it out. If you are pretty sure it has, just prune back the damaged stem to the nearest pair of leaves, or remove the branch entirely, as warranted. 

So how much are all these torrential rain storms we've been having going to affect my home garden garlic crop?? They're shooting out scapes, which I've been enjoying thoroughly, but I know garlic doesn't like wet conditions when setting. Any advice or do I just have to wait it out and hope for the best?

The garlic, as you say, doesn't like the sogginess at this critical time. I would just wait for it to turn color, signalling it's ready for the bulb to be pulled. Next season, add lots of sand and other coarse material to the garlic bed to help the garlic through that important  early summer period. 

Hi Adrian, I ordered some Mary Washington asparagus and planted them about a month ago. I've never grown asparagus before but ferns have come up. Any recommendations to keep the plants happy and healthy? I need to wait two years to cut the spears, right? Thanks for answering.

The standard advice for asparagus, as  a perennial green, is to really prepare the bed beforehand, making it deep and rich. I would make the bed no wider than four feet (but as long as you want) so that you can weed by hand on either side without getting into the bed. Weeds can be a real problem in establishing an asparagus bed. I would not harvest in any quantity until the third year. 

Our lawn would not entice goats to eat. We have every weed growing and no grass. Neighbors chose to remove their weeds, put down soil, and reseed. Grass is now growing. Is this a task to tackle now with summer heat coming or should we wait until September? When is the best time to move a peony? It is healthy but receives too much shade from a large oak. Thank you so much!!

Now would be a bad time to seed your lawn -- the best grass around here, believe me, is a cool season type called turf type tall fescue.  Wait until early September to do the bed preparation and sowing. If you are planning on a wholesale herbicide treatment of the area, make sure you do it early enough that it won't affect seed germination. You can renovate lawns at this latititude from Labor Day until Halloween. The earlier the better, though, in that time frame. 

I'm not a gardener, but after years of embarrassing my neighbors, I finally pulled up the terrible overgrowth in front of my house this spring and replaced it with a few miniaturized hybrids of easy-care shrubs in the hopes that even with my lack of skills and attention they'll look presentable but won't get as unwieldy as their predecessors. I barely got them in the ground before this spate of constant rain. I know if it were dry I'd need to water them until they were established (however one determines "established"), but can I do anything to prevent them from drowning? The bed is slightly raised, but the soil in my area has a lot of clay, so there's only so much draining. There's a layer of mulch on top, should that stay indefinitely? Does it need to be replaced periodically? How often? Do the plants ever need a break from it?

Lots of strands in this one. Yes, our heavy clay needs major amendment for most ornamental plants. If you have genuinely unfixable wet soil, it would be better to plant shrubs that can take drought and flood, things like winterberry holly, myrica, inkberry, shrub willows. Mulch should not be renewed until it breaks down, and too much shredded hardwood mulch laid year after year can cause harmful levels of manganese to build in the soil. Much better to mulch with compost or leafmold.

My first attempt at getting a draculus vulgaris to grow has turned out good and bad. It "bloomed" but the bloom only last a few days. Is this typical? Should I have planted two or more bulbs for pollination?

This is an aroid that I have not grown. I thought it would bloom for a longer period, but perhaps the heat hastened its demise. 

I have 6 eggplants in my garden that are desperately trying to survive the onslaught of little black beetles (flea beetles?) that are eating their leaves into lace. I've been using a spray on the leaves, the recipe for which I found online - 5 parts rubbing alcohol, 2 parts water, and 1T dish soap. It works for a brief period, but the next day, or after rain, the bugs are back. Do you have any suggestions for keeping my plants safe short of standing guard 24/7? Thanks!

I'm not sure that the rubbing alcohol in a spray would be too good for the plants. Cut back on that. If the eggplant is growing in good soil in full sun, it will soon outgrow the damage, which is worst when they are set out as tender transplants. They will benefit from a tomato feed.

Hi Adrian. I'm lucky enough to have lots of pepper plants in my veggie plots. I always struggle with the question of whether--and how--to stake them. Best done now, I think, before the roots really develop. Any suggestions on the best way to stake? Thanks to a neighbor's bamboo infestation, I have access to lots of bamboo poles of various diameters...

Excellent question! I am putting out my pepper transplants now (finally). They really do benefit from some advance staking, but they don't need the heavy duty supports that tomato vines need. I find that the small tomato cages (too small for tomatoes) are perfect for pepper plants. I have also used a simple stake -- a 5 footer pushed in one foot -- set a few inches from the pepper stem and tied as the plant grows with twine. 

We purchased and planted a Knockout Rose a month or so ago. It already is looking like it is dying as there are stems withering. It bloomed briefly. The nursery gave us a guarantee. Any ideas? I understand Knockouts have a few problems that can go wrong. Our neighbors have beautiful Knockouts.

Are you referring to the natural cycling of the blooms or actual stem wilting and stress? Knock Out is a pretty bulletproof rose. Roses in general need full sun and soil that drains but will hold some moisture. (Clay enriched). A rose in wet soil will die.

Do you recommend heavy mulching to choke out weeds in an asparagus bed, and if so, what kind(s) of mulch?

Yes, I might use straw in the first year, or again, the catch all leafmold. 

Just wanted to say one of the reasons I'll pay for the WaPo online is to have continued access to experts like you. Opinion columnists can be fun to read, but my real learning comes from pros like you. You (and the paper) are appreciated!

Well thank you! Nice to hear.

Hello! I read an article that suggested that light exposure for lettuce was a greater factor in bolting than heat and I wondered if you had any success with this?

Afternoon shade may delay bolting, but believe me, lettuce is going to be bolting in the next couple of weeks. I would pull it and plant some carrots or something. 

I've found that spraying with neem oil (I use "Safer GreenGuard") gets rid of most bugs, but I haven't had flea beetles. It's worth a try, and better for your plants than rubbing alcohol.

Yes. Neem oil will discourage them. But once the plant sets more leaves, I'd forgo that. 

OP here. Yes the idea (German for "hill culture") is that burying logs/branches/wood chips etc. under soil, leaves, grass clippings, mulch, etc is not only supposed to provide long-term organic matter but also helps provide drainage (I think) and lessens watering since you are supposedly unlocking the water held in the wood as the wood rots over time. Just thought though that it was an interesting idea to test out, especially since my part of MoCo is afflicted with clay soil and would be a good way to use something I usually just toss in the lawn/leaf can for the County to pick up. And yes I would be amending whatever soil I dug up with compost I already have on hand, since it's not like I have a surplus of good friable soil to begin with anyway. :-) Potomac, MD

I'm sure the rotting wood will feed beneficial soil fungi and bacteria. Some of the images I have seen seem to have subordinated beauty for function.

When I traveled in Thailand a few years back, I took so many pictures of orchids, everywhere - hanging from lightposts in the street, decorating the outside of shops, in medians on busy streets. They were beautiful and stunning and were totally taken for granted. Then our guide took us to a famous garden, named after a Queen of Thailand, and it was called, I think Exotic Garden or Exotic Flowers or something like that. It was filled with... gardenias, petunias, daisies, hydrangeas and the like. Very beautiful, but not exactly what I thought of when I thought of "exotic". But I guess if you're surrounded by orchids all the time, then gardenias ARE what's exotic! (That's all. No question.)

One of the downsides of our love of tropicals -- bananas, coleus, cannas and taros, for example -- is that every place around the globe looks like every other place. Maybe that doesn't matter if you love your little corner of paradise. 

Any suggestions for asparagus beetles? I'm trying (again) to get an asparagus patch established, and these varmits were my problem last year.

You could try neem or horticulutral oil, or even insecticidal soap (all organic). Good sanitation is also helpful. Make sure all the dead top growth is removed over the winter. 

I have some hostas that have thrived where they were planted. So much so, that they need to be thinned. I have some bare area to transplant those that are separated, but I don't know how to do it and when is the right time to do it. Thanks!

If you are careful, you could lift and divide them in leaf, and give them lots of water and mulching in their new site. If you can I would wait until September to do this. 

Dust with rotenone periodically?

I don't like rotenone. I think it's nasty stuff. http://www.ncbi.nlm.nih.gov/pubmed/19385059

We have a "volunteer" wild black cherry that has grown enormously over the past few years. It's healthy and we like it, but due to its growing canopy it shaded some of our lilacs so they stopped flowering. I moved them to a sunny spot, but am wondering what perennials might do well in the shade, and that I can plant now. Any ideas? Also, the transplanted lilacs are healthy but got pretty leggy. Should I just leave them as is and see how they do next spring?

Perennials for shade? Lots of choices, hostas, ferns, epimedium, solomon's seal, heuchera, hellebores, to name a few. I would leave the lilacs. The black cherry produces a lovely timber but the tree is rather weedy and attracts the tent caterpillar. 

Hi, I have a 5 year old coreopsis plant that is not growing back in my garden. And last spring I planted 3 more in another area of my yard, and I don't see them. Any thoughts on this? I have a major bunny problem; maybe the bunnies ate them? Already, the bunnies have eaten the tops of the new coneflowers I planted on Sunday! Darn bunnies!

I think the only satisfactory way of dealing with bunnies is to exclude them with fencing. I'm developing a story on this at the moment. Perhaps you would like to email me your locale, extent of problems etc. adrian.higgins@washpost.com

I'm usually a pretty good gardener but a friend had a question that stumped me. She has been trying to start a cutting from a family wisteria plant for several years now with no luck. She has followed all the conventional wisdom to start one of these plants that I've been able to find in my books and on the internet (these should be harder to kill than to start). She has tried new shoots, old woody cuttings, used rooting powder, used long and short length cuttings, tried digging up new shoots at the root area, but they all die. I recommended trying "air layering" or standard layering as possibilities since she'd tried all the regular stuff. Any other suggestions?

I was going to say standard layering, where you cut a longitudinal slit on the underside of a branch and peg it to the ground until it roots. At which point you lift a whole new plant. 

The most bolt-resistant (relatively speaking) leaf lettuces I've found are Buttercrunch and Red Sails.

Perhaps. My main lettuce season is the fall. I find that by sowing seed in mid August, I can get lettuce through to the end of the year. I love Winter Density. 

We are heading out for a week in Portland, Oregon, the Rose City. I know the annual Rose Festival is over, but where would you recommend we look for the best public gardens starring roses?

Gosh. There's a place called the International Rose Test Garden. www.portlandparks.com. Check it out. Alas, we have reached the end of our allotted time.

Gosh. There's a place called the International Rose Test Garden. www.portlandparks.com. Check it out. Alas, we have reached the end of our allotted time.

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Adrian Higgins
Adrian Higgins is The Washington Post's gardening columnist. Read his recent story on advances in the old fashioned iris and follow him on Twitter.
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