Adrian Higgins gives advice on grooming your garden in the summer

Jul 21, 2011

Learn how local homeowners are reducing the amount of rainwater leaving their property with beautiful rain gardens, and get summer gardening advice.

Hi, everyone. Thanks for joining us for the chat today. Today we wrote about how to install a rain garden and, moreover, explained what a rain garden is. I hope you had a chance to see it, either in print or online. The next six weeks are among the most challenging for the gardener. We have to work at producing something beautiful in the dog days, but that can be achieved beautifully.  Let the discussion begin...

Dear Mr. Higgins, I was given a hydrangea that is supposed to have blue colored flowers. I heard treating the soil would ensure the blue blooms. What do I need to do? The soil in the yard is typical of the Seventies subdivision: a heavy brown color with a high clay content under sod.

The mophead and lacecap hydranges are part of the bigleaf hydrangea tribe. The preferred blue hue is only achieved in acidic soil, the more alkaline the pinker. In our typically mildly acidic ground, the color is purplish. You can acidify the ground with aluminum sulfate, or regular top dressings of compost. I think the native pH will win out eventually. I'm actually becoming captivated by other hydrangeas such as the Annabelle and Limelight types. 

What do you think about planting white clover seeds in place of a lawn? Other than mowing it, we're not very good about keeping up our lawn (aerating, weeding, fertilizing, etc.) and we don't want to pay a service to do it for us. Would a clover lawn be easier to maintain?

Yes, it would be, but many people find a  lawn mostly of white clover to be unsatisfactory. With lawn renovation season coming up, you may want to try again.

Am I glad to see you online today! I carefully planned and then planted a shade garden . . . .and then sat back and watched a good bit of it disappear. My hostas are pretty much gone and now the voles are starting on the ferns. I'm quite sure it's voles. (I can see the holes they are making and the plants are dying because the roots have been eaten.) I'm pretty sure there's not much one can do about voles that isn't super toxic. If that's the case, is there anything I can plant in a shade garden that voles do not like? I have heard they like plants with fleshy, bulbous roots -- like hostas.

Voles love to eat the roots of hostas and other perennials, as well as bulbs. Sounds like you have a real problem. Whatever you plant, I would surround the rootball with a good barrier of gravel, and allow for root growth. I would try ground cover euphorbias, I have to believe the milky sap would turn them off.

I have a small strawberry patch raised bed. This is my second year, and I was looking for many fruits this year. I did mulch and the fruits were not touching ground, but they were all eaten by something by the time they were ripen. They all have several holes, and it looks like they've been eaten by bugs. (Not birds or animals for sure, since fruits are still haging on.) Today, I finally saw slug coming out from a strawberry! If the slugs are eating my berries, what would be the best organic way to keep them away?

I say it's almost certain slugs.  You can use an organic slug poison called iron phosphate. Anything you can do to keep the fruits off the ground would be helpful and drip irrigation would allow you to water the roots without the foliage. That would help too.

Adrian, we came back from a two-week vacation last week to find our 8-year0old sour cherry tree missing nearly all its leaves, and those that were left were brown and shrivelled. It's strange because we had a bumper crop of cherries in June. I noticed a few yellow leaves before we left, but nothing that seemed abnormal. Any idea what happened and do you think the tree is dead or might come back? Thank you.

It could be a number of things, prunus is notoriously prone to pests and disease. It might be Japanese beetle, fall tent caterpillar or inch worms. Prunus will also drop leaves when stressed, though we haven't really had the drought conditions that would trigger that. I don't know if you have a lawn service, but if you do, check to see what they have been spraying in your yard. A new herbicide called Imprelis has been linked to widespread tree defoliation. Your tree may leaf out next spring, don't give up on it.

For rain gardens we recommend to residents digging about 6"-8" in saucer shape, not bowl shape, and emphasize planting native plants, which don't need amended soil. Not sure about the 18" to 45" you mention.

I wish we could put to rest this idea that native plants don't need any special cultivation.  A well grown garden plant needs all the help it can get, including steps to improve the nutrient, moisture and oxygen retaining qualities of the soil. 

Good afternoon! I have a September Charm Japanese Anemone by my front door that is rapidly outgrowing its space (didn't know it was invasive when I planted it). I don't want to destroy it but would like to move it out of that spot because we feel like we are walking through a jungle. It's getting ready to bloom. Could I safely transplant it after it is finished blooming? I want to plant a boxwood in that space before winter. I live in Zone 6. Thanks for your help!

Wait for it to bloom this season, and then dig and divide the anemones, cutting back the tall stalks as you do. 

The hydrangea flowers are turning brown. They are in part-shade and I have been watering them. How much water do they need? Thanks.

Some hydrangeas go through a sequence of flower color as they age, ending in brown or tan. Yours may have reached that point. Sounds like it might be oakleaf hydrangea.

I have a small little "umbrella tree" (camper down elm) in my front yard which I love. It is prone to and infested with scale. I finally resorted to expensive chemical ground injections from a tree care company this last time around. Am I destined to fight this forever?

I don't think I know this plant, do you have a botanic name? My view is that unless you have an old, irreplaceable tree, keeping something going with soil injections is simply an admission that you have the wrong plant in the wrong place. 

This hot weather is prompting me to get rain barrels for my gutter downspouts. Last year I was surprised to learn that rain barrels are illegal in many western states. You're not allowed to capture water. You have to let it go back into the ground and the water table.

This is amazing. Water so precious you can't capture it. I'm not sure I could live in such a place. One vital thing to remember about rain barrels here: Keep them covered to avoid mosquitoes and to avoid small children getting into them.

I'm already thinking of cooler days and of trying to get rid of the clover and other broadleaf weeds that have taken over my yard here in Charlottesville. How difficult will it be to use organic broadleaf killers and then amend the soil and seed anew? Or might I be better off tilling everything under, amending completely and starting fresh? What's the tipping point for one method or the other? Many thanks.

The rule of thumb is that if at least half your lawn area is thin and weedy, you should start again in early September by removing the vegetation, tilling the soil and seeding. There aren't that many organic herbicides out there. Contrary to what you read elsewhere, even in this newspaper, vinegar off the shelf isn't going to be effective against weeds. The acetic acid used organically is much stronger than the vinegar one buys in the store. Roundup is used by a lot of folks because it works fairly quickly and breaks down quite quickly, unlike other herbicides. But it is time to be thinking about killing what you have so you can move forward in a few weeks.

I was happy to see the rain garden feature, but I think it is a little involved for most folks. Would merely adding some of the plants from the resources help with soaking up excess water--without the excavation, etc.? I have a somewhat "swampy" area in my yard, yet to be landscaped, and I was hoping to just create a bed of water-loving plants--saving my back from all that digging and saving the costs of regrading the lawn. Creating the bed would involve amending the soil, so I expect it would improve drainage. It seems shrubs versus weedy lawn and day lilies would be an improvement regardless. Not that it would matter this summer! I live in fear of the water bill's arrival, though I follow recommendations such as a.m. or evening watering, being generous with the mulch, etc. Unfortunately I picked this spring to double the size of my vegetable garden and greatly expand my perennial garden!

Lots of ponts here. It was dry in May, a key seed germinating period, so that was a real problem. Though it has been hot, we are not in a drought. The difficulty with waterlogged soil is that you are restricted by the types of plants you can use there, because they must endure flood and drought. The beauty of a rain garden is that it drains but keeps the ground moist for long periods, this allows a much broader palette of plants. Also, ironically, a wet area is not a good location for a rain garden because it won't perc as well as a drier one. The object is to put the rain garden uphill of the wet area so that you drastically reduce the amount of moisture getting to it. The manuals referenced in the stories online will explain this better.

How long does it take after planting a raspberry plant to get berries? This is my second year and the bushes are beautiful but no raspberries! Can you plant blueberry bushes in the same bed and or near the raspberry bushes? I live north of Boston, Mass. Thank you.

You have to wait at least two years to get a decent raspberry harvest, and preferably three. Here's the consideration: For regular, early summer bearing raspberries, you have to keep canes that grew the previous season, though they can and should be trimmed back. If you have late summer/fall raspberries, called everbearers, you can mow the lot to the ground in late winter. Find out the variety you planted. 

I have been hearing about the Giant Hogweed plant. It seems quite frightening. How does one get rid of it should it appear nearby? Is there someone to call?

It is a monster weed whose sap can cause skin irritations. If you can feel you can do it yourself, wear long sleeved clothing and use gloves. 

I just found tiny little black bugs crawling over my basil plants yesterday. I've never seen them before. Any ideas on what they could be, and how I can save my plants?

They may be aphids. YOu can spray them off with a gentle jet of water. May planted Basil is at the end of its game. I would keep cutting it back to promote branching and delay flowering, or plant some fresh. Some supermarkets sell young rooted basil as a fresh herb. It's easy to separate each plant and stick it in the ground. 

I grow a lot of radishes. I plant them in the rows of the seeds that are slow to germinate such as parsnips and parsley. Sometimes they form good bulbs for harvesting, but sometimes all they do is grow foliage, go to seed and provide no edible root -- all in the same raised bed. Any idea what's causing this?

Radishes need cooler temperatures and colder soil to develop well, along with even moisture. Any dry or heat stress will turn them pithy or prevent bulb formation. I would wait until late August, early September before sowing a fall crop, and then make sure they don't dry out (without drowning them). 

Professor, I bought a weeping pussy willow that doesn't weep. One small branch is weeping but the rest of the tree is standing straight up. I bought it from a mail order catalog and when it came it was just a small branch that I stuck in the ground. Was I supposed to be training it to weep as it grew? If so, I didn't. Is there anything I can do now to make it weep?

The weeping quality is the mutation of  branch that has been cloned to produce a weeping tree. You can't make a normal, upright branch to weep, not even by reading it some Jeffery Archer. It is not uncommon for some of the branches of a weeping plant to revert to the normal state, at which point the errant branch should be removed. 

My property borders a detention pond. My yard leads to a chain-link fence and on the other side is a six-inch-wide berm held up by railroad ties. The property owner will mow the other part but not edge along the berm, so I've got wild, poisonous weeds along there, creeping into my yard. Is there something I can plant in that are -- full sun, well-drained soil -- to spread on both sides of the fence to keep the weeds at bay? Thanks.

Rain gardens have become popular because many landscape architects feel the old model of the detention pond is an aesthesic disaster. If the encroaching weeds are vines, it sounds as if they are, it is tougher to put in a plant barrier against them than if they were simply shrubby or herbaceous weeds. You could try a closed fence (not wire), or a feature such as a xeriscape, rock garden like, bed. I have this problem in my community garden, and I just pull the encroaching bindweed, porcelain berry etc. once a  week.

My beautiful 3-year-old Japanese Magnolia (approximately 6-feet-tall) was transplanted to my front yard, against my better judgment, in April. Eventually the green leaves curled and fell off, and now it is entirely bare. I keep watering it, hoping there is life in there somewhere, but hate to keep a dead tree in my front yard until next spring. Is there a way to tell without digging it up?

You can scrape the bark with a penknife or your thumbnail and look for green tissue below.

What was the white flower on the cover of the Local Living Section? The red one was a scarlet lobelia, the purple one was some type of blue flag iris, but I couldn't place the one white.

I think that was clethra, summersweet.

How do I create a rain garden in an already established area with a lots of plants thriving in it? I get a lot of run-down rain water from my neighbor's yard, which seats slightly higher than mine. With heavy rain the mulch or rocks in my dry stream wet washed away. Any suggestions would be appreciated.

The key to a successful rain garden is the initial excavation of  heavy soil and backfilling with the soil mix mentioned in the story. To that end, you would have to lift and set aside your plantings before putting them back. They can be stored in mounds of soil and mulch, as long as the roots are not exposed, and are kept moist. 

We have extremely hard water and have installed a water softener. I've been told by numerous people not to water my flowers and vegetable garden with this water as it will harm the plants. True?

Yes it will, the salts used to soften the water is harmful to plants.

Now I wanted to know your thoughts on how to handle excavated soil from a rain garden hole: if it's as common in D.C., there's not space in the yard to put it and it's more than you can use in a berm.

You can pay for folks to haul off excess soil, especially the crummy type typically found in an urban yard. I think one of the owners had to deal with this, Jamal Kadri, and I don't think he would mind me sharing his email address:

Do you have a cat? My neighbors' cats took care of my vole problem! My "lawn" contains a good bit of clover -- though it is not all clover -- and I find it very satisfactory, as do the honey bees!

There you go. Tackle the voles with a cat. When I had a cat, the vole population was reduced, no question.

Mr. Higgins, what do your suggest as the appropriate watering cycle for lawns and garden beds in this heat?

First, I would water early in the day, and try to avoid wetting foliage. Hand watering is most efficient, a hose wand is a great way to deliver a lot of water gently. Containers need watering at least once a day in this heat, lawns just once a week, but they should get a good soaking. You need to get the soil wet down to four inches, and use a screwdriver to see if that has happened. Generally, the smaller the container or the poorer the soil, the greater the need for water. 

There are hotlines to call in certain parts of NY. They ask that you call and photograph it.

There you go, thank you.

Last year the heavy snow weighed down my side bushes around the perimeter of my small lawn. They are now brown in several places and out of shape. How do I get them looking green and healthy again?

The first thing you should do is cut out all the dead wood. This will allow the vegetation to fill in over several years. Speaking of deadwood, I better sign off. Thanks for all your questions. Stay cool. Keep watering.

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Adrian Higgins
Adrian Higgins is the Washington Post's gardening columnist. Read his latest story on rain gardens, and watch his latest video on caring for tomatoes in his community garden plot.
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