Adrian Higgins gives advice on grooming your garden in the spring and summer

May 19, 2011

Find out which plants, besides impatiens, are best for a summer shade garden.

Read Adrian's latest story "Impatiens' lovely bedfellows"

I'm thinking of covering patio tomatoes with tulle netting or something like that to avoid insect/stink bug damage. Will they get enough sun through the netting to produce? If not do you have any products you recommend for the problem?

Hello everyone, thanks for joining our spring chat. Stink bugs not only invade our homes in the fall, but do real damage to certain edibles, particularly peaches. I don't think it's necessary to cover the tomatoes, they grow so vigorously that bugs should not be a problem, especially if you monitor them often and physically remove and kill the bugs as they appear. Tomato plants may grow under row covers, but the flowers need pollinators to shake up the pollen.

Good afternoon, Professor. I am now in the process of planting my annual flower bed, full sun. I purchased dwarf dahlias last weekend and have planted them in the front row of the bed. What would you suggest for the rows behind them?

There are so many wonderful zinnias these days, they bloom their heads off. I'm also about to sow seeds of smaller sunflowers for my garden. I love Italian White, which  grows to about five feet.

Can I transplant fountain grass now? It hasn't started greening up yet. Will it do okay in a mostly shaded area? Thank you!

You can transplant it if you are careful to dig up much of the root ball, or you can simply chip off a fair sized division and plant that. Unfortunately, while pennisetum can take a little shade, it will look feeble and floppy in a dark bed. If you want a grassy effect in deeper shade, I would go with hakone grass or various sedges.

Last year I saw Shinto moss gardens in Japan. Is it possible to create a moss garden in our area? Which type of moss would you recommend? Are native mosses available?

Moss gardens struggle in our hot, humid climate. Even the native mosses in the mountains here retreat in drought and heat. You can certainly have a fairly pretty moss garden if you are diligent about removing leaf litter and weeds, and watering regularly. I would advise starting in a small area and see how it does for you. There are moss nurseries out there, you'd want to make sure you're getting a species suited to our region's climate and soils. Has anyone else tried growing moss in Washington?

Can you advise on environmentally safe weed killers and where to locate them?

Corn gluten is an effective preemergent herbicide. Vinegar will work on growing weeds, but not household vinegar, it's not concentrated enough. Check out East Coast Organics, see what they have. Another option is to use a propane weed torch or to hand pull.

I need low growing evergreen foundation plants for my partially shady front lawn. Any suggestions? Thank you.

I would consider ornamental gingers, ajugas, epimediums and leadwort.

What would be a nice low-growing, shade-loving plant for the front of the house?

I have grown dwarf nandina in shade, as well as hellebores, camellias, the aforementioned hakone grass and epimediums. Lacecape hydrangeas or Annabelle hydrangeas will work in partial shade.

Thank you for your article that goes beyond impatiens for colors in the shade. I discovered coleus last year and greatly expanded my plantings this spring. I am now interested in heucheras, but you made no mention of them in the article. Are they viable for container planting in this region? Also, my go-to spiller in the shade is torenia, but it is increasingly hard to find. Any sources?

Thank you. I didn't recommend torenias because I fear they don't perform well in our heat. I have heard very different accounts of how they perform here. Any observations out there would be most welcome. Heucheras are good shade perennials but many don't last long here, mostly because they are in soil that is too wet. Villosa types do well. I saw a variety the other day called Montrose Ruby that seems to be happy if given the right conditions.

I am thinking of adding a hive this fall for garden pollination. What do you think?

I've only kept honeybees, which are definitely started in the spring at the start of the egg laying season. I don't know if a fall management of orchard mason bees would work.

Friends are getting married and have asked for no presents. They are avid gardeners, and we'd like to 1) disobey their wishes and 2) disobey by getting them a tree, planted by us, on their large property (location of their choosing). We would like to work a conversation around their favorite trees, but in the event that doesn't happen, do you have suggestions for native trees that would work in a landscape, either as a shade tree or ornamental specimen? They are in zone 6b-7a. We wouldn't do this if we thought they'd be offended; Knowing them, they don't want their guests to do anything for them but would be delighted with a gift of this nature (so to speak). My husband is partial to the red Buckeye. We have a couple and they're gorgeous in the spring, but not much to look at in the fall. I'm partial to Franklinia and Fringe trees. Other thoughts? Thanks!

This is thoughtful, but predicated on a) the recipients being in one place for a long time or b) the plant being amenable to transplanting when they move. I love the red buckeye, stay away from the horse chestnut. Make sure the fringetree is the native shrub, not the Asian tree. Franklinia is special but difficult to establish. There is a native stewartia shrub that might be good to consider.

Hello! So glad to see you! I am seeking three to four foundation shrubs that can grow up to 5' high. They will face south and the hot afternoon sun. I've tried Japanese hollies twice, and they all died. I tried Chinese hollies, and the deer decimated them. Would mahonia aquifolium work? Do you have any other suggestions? Thank you so much!

Yes, mahonia would work, but you need to cut them back hard after fruiting to prevent them from getting too leggy. Trite, but I really value nandinas for difficult spots like that. Dwarf forms of crape myrtle might be a good choice.

I am growing green beans in my garden and the leaves appear to be getting eaten up. There are bites taken out of the middle of the leaves. What could be attacking my plants and what can I do to prevent these pests from eating up my bean plants?

It could be slugs or bean beetles. Start with great soil so they can outgrow these munching pests, and do inspect the leaves top and bottom for insects and eggs. Do this when the leaves are dry.

Greetings from Mount Prospect, Ill. In the fall of 2009, I planted three sky rocket junipers on the south property line of my house. They were beautiful and healthy until the winter of 2010-11 struck. Now they are green at the crowns but pretty much rust brown every where else. Will water and fertilizer do the trick or have I lost them?

I think even in Illinois, there is enough heat and humidity to do these plants in. They are native to dry, sunny, Western states and soon decline in hot clammy climates.  They look awfully pretty in the nursery, where they should stay. I would go with perhaps a thuja or red or white cedar in their stead.

Hi Adrian! Last fall, I received a gift of iris bulbs from my father-in-law. These bulbs have been grown, divided and shared among my husband's family for many generations in the Lake Erie area of Pennsylvania. I planted them in my garden here in Northern Virginia last fall, and they have thrived -- well, the leaves have, anyway. They've grown very tall and are nicely green. But the flowers never bloomed! I can't imagine I killed them, since the greens grew well, but is there a reason the flowers never appeared? Is there anything special I ought to do with them? I watered them with fertilizer that was marketed for new transplants, but otherwise they've just been hanging out in the soil getting regular water.

I don't know if these are true bulbous irises, which bloom in late winter, or the bearded types now in flower. It might be a case of them needing a year or two to build up enough reserves to bloom. If bearded rhizomes, the key is a well drained bed, especially in winter. Don't use a high nitrogen feed on them.

The tips of my clemetis vine (with buds) are wilting. Is this fungus? How do you suggest that I control the wilting? Thank you!

This is classic wilt disease on large flowering hybrids. Cut the wilted stem below the wilt, but sterilize the pruners between cuts (in alcohol or chlorine solution). Some gardeners drench the roots in fungicide. The real solution is to plant smaller flowered clematis that are more resistant. Joy Creek Nursery always had a splendid array. http://www.joycreek.com/

I have planted a few perennial flowers but most of the packets say that the flowers will only bloom the following year (ex. poppies). Could you explain to me why that is please?

They tend to be hardy annuals that need a period of chilling for the seed. Thus, you sow them in the fall or late winter. Once you have a good stand, they will reseed each year provided you don't cover the ground in a thick layer of mulch. 

Is there any advice for a backyard that supports two dogs but the owner wants to landscape it nicely and have it look good as well?

Many gardens coexist with dogs. The key is to minimize the amount of open soil (good for weed control too) and not to let the dogs roam in the garden all the time. My dog is only in the garden when I am.

Impatiens are great for partially shaded gardens but are there ANY colorful perennial plants that flower for an extended period, i.e., through the summer?

Not too many, and the point is that whether you go with perennials, annuals or grasses and shrubs, the most satisfying course is rely more on leaf ornament. Tricyrtis, persicaria and hardy begonias offers perennials blooms in shade, along with leadwort. 

Where can I go for help in identifying green things that are beginning to come up in my garden/window boxes as to whether they are weeds or possibly interesting/desireable plants ?

I would take specimens to your local plant clinics run by county Master Gardener programs.

What causes yellow leaves on hydrangeas? I have a row of healthy green leafed ones and one yellow leafed one. They all get identical care and fertilizing.

Could be lots of things, including really poor drainage or high soil pH. It might also be a lack of nitrogen or magnesium. I would get some nice compost, mix in some Epson salts, and spread it as a thin mulch.

Hi, Adrian. When the new leaves emerged on our maple tree this spring, they had brown spots and were curled up and dark brown along the edges. Other maples in the yard are not affected. I planted some archangel under it earlier in the spring. Would that have caused the problem? They were just small plants. Thanks for your help.

The archangel would not have a bearing on this. It's probably a leafspot or anthracnose disease caused by the cool, wet spring. The tree will regrow leaves if it needs to, and if you keep it lightly fed and watered as needed, it should be ok. I wouldn't spray.

I live in a town house and the small front yard is mostly shaded by a cherry tree. What shade-tolerant plants would you suggest that would create year-round interest and eliminate the need to mow this small yard without damaging the tree?

Lots of already mentioned shady ground covers. I just love epimediums, small leafed hostas, foam flowers and leadwort. Be careful not to damage the root system when you convert from grass to bed.

Please advise as to the best way of getting rid of chipmunks. They are digging holes in my flower beds and near the base of the bushes. Each year these holes keep getting wider and deeper!

I live with them, but I'm not over run. Does anyone have any ideas?

What is your opinion of the popular hanging tomato devices in which the plant grows upside down ?

Complete and utter rubbish.

What other options are there when Bishops Weed is found growing between the impatiens in the summer shade garden? Is Round Up the only solution?

Round up would work, I suppose. You'd want to try and dig it out and soon as it sprouts in late winter, and then prep the bed for your summer annuals.

Mr. Higgins, I planted my vegetable garden in early May knowing it was too early for tomatoes, etc. based on your advice in previous chats. However, I have a new baby and my parents, who are excellent gardeners, were visiting and wanted to help. Now after a few weeks of cool rain and tomato plants that are looking at me like I've done them wrong, I see that your advice should always be heeded. My question: Can you predict other things as well as the weather? Can you give me some lottery numbers?

What can I say. I think Somerset Maugham said there are three rules for writing the perfect novel, but no one knows that they are. Mine are still in pots, outside, but seem to be responding to something. I was going to put them in this weekend. I would hang tight and see if they come back. I can't give you lottery numbers but I can safely predict your baby is going to grow up to be a fabulous gardener.

Are there any plants that dissuade mosquitoes from coming too close?

Not really, there are some whose oils they don't like, but you have to break the leaves to release the oils. Scented geraniums are a good example. Thyme too.

I have cabbage and brussel sprouts that have holes all over them from being eaten by something. Same with my rhodedendran. What can I use to prevent them from being eaten and I can eat the cabbage?

You have at least two different pests at work here. The cabbage and broccoli are the victim of the cabbage worm butterfly, I suspect, while the rhododendron has its own leaf eating beetle. The edibles can be eaten, just examine the leaves carefully for green caterpillars in various stages of growth and remove them first, unless you like a little extra protein.

Are there any types of salad greens that would be appropriate to plant now or have I missed the boat for this year? I already have loads of romaine, red leaf lettuce and swiss chard growing but I am hoping to grow greens like arugula, mesclun and escarole. Also, I am planting tomatillos and, although I have read that they should be planted two to three feet apart, I haven't been able to find out how far apart the rows are supposed to be. Do tomatillos tend to grow successfully in the D.C. area? Also, are tomatillos cross pollinating? (I have read this all over the Internet but wanted to check with you.)

I would not sow lettuce now, but wait until August for a fall crop. Arugula is in the same boat. For greens now, I would consider kale (eaten at baby stage), chard and maybe beet greens. Collards are a good choice. Tomatoes and tomatillos both do best with some elbow room. I would space rows at least three feet apart. Tomatillos grow well in our area and are self pollinating.

I bought some scallions from my local farmer (picked that morning) and planted them in a window box. I read somewhere that they would continue to grow. The tops (the green part) are all brown and wilted. What did I do wrong?

Alliums tend to react to transplant shock by showing brown tips. You can trim them off if they bother you.

I enjoyed your weekly groundwork blog the last two years. Are you no longer doing that?

The candid answer is I don't know. I think it provided a lot of help but was getting too few eyeballs for the amount of work involved. I don't know whether to restart it. We have been doing videos of me in the garden. Two so far this year and another in the works. I'm open to suggestions and feedback.

What's the best-looking way to keep my rugosa roses under control? They're gorgeously messy and smell great (and so low-maintenance, which has been important as I've been quite sick this spring). At this point, though, they're so top-heavy that the thorny branches all bend into and block the only path through the garden. Should I tie them or use bamboo stakes or build a high fence around them? Thanks. I always look forward to your chats.

You can trim them back after blooming. Then mark your calendar to do some serious winter pruning next January or February, on a mild day. Take out the old thick canes and trim back the keepers.  I wouldn't stake them.

I have a brown thumb. I would like to find a large houseplant which I can sit on the floor and bring some natural beauty to our family room. The room gets moderate light. Any suggestions?

Try a philodendron.

Time snuck up and they are huge. Is it too late to divide them?

If you are careful not to damage leaves, and coddle the divisions with compost and water, you should be all right.

Does D.C. have any clinics that you know of where I can get plants and soil analyzed?

Yes, UDC has a cooperative extension office. 202-274-7166.

Go on. Tell us how you really feel. :)

Oh Ok. I think it's a gimmick. If you can't place a tomato in the ground, that's fine, give it a good amount of soil in a container and let it grow the way nature intended. A hanging basket is the most stressful environment for any plant.

Hello. I have problems with both chipmunks and squirrels, and after a lot of experimentation, I've found that sprinkling cayenne pepper on the soil deters them.

Great. Thank you.

My basil is starting to look yellow green rather than a rich green. I have read that this could be caused by over watering or under watering. What do you think would cause this discoloration and what can I do to get my plants back to their rich green color?

Gosh, we're out of time. Basil has been set back a bit by the cool temperatures and rain. The best thing to do is to leave it alone and let the soil drain and warm, this will promote fresh growth. Thanks for joining us today.

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Adrian Higgins
Adrian Higgins is the Washington Post's gardening columnist. Read his latest story on plants for the summer shade garden.
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