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“Dear Ruth” Column

Category: 'Dear Ruth' Column, Presenting "The Curious Gardener"

The Curious Gardener Newsletter

The “Dear Ruth” Column for Gardening Questions

Ruth Rogers Clausen is a horticulturist, journalist and author who is partnering with Womanswork to produce the “Dear Ruth” column.

Ruth grew up in Wales and studied horticulture at Studley College in England. She has contributed greatly to her profession as a writer of tomes (Perennials for American Gardens, Random House; Essential Perennials, Timber Press); an editor of gardening magazines; and a lecturer, advisor and judge for botanical gardens and flower shows all across the country and around the world.

For many years Ruth gardened in Westchester County, NY (Zone 6), and more recently has been gardening in Maryland where she grows an eclectic range of plants. Her plant choices reflect those plants that do well in her region and throughout the northeast and mid-atlantic.

Ruth wrote a book for Timber Press titled 50 Beautiful Deer-Resistant Plants: The Prettiest Annuals, Perennials, Bulbs, and Shrubs that Deer Don’t Eat, and more recently co-wrote with Tom Christopher a book, Essential Perennials, also for Timber Press.

Write your questions in the Comments section below and Ruth will respond in a timely manner.

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205 thoughts on ““Dear Ruth” Column

  1. Maureen Workman says:

    Dear Ruth,
    I have hydgrangia in full sun in front of my house. They are pink and only give me one flower each. They been there six years , after being moved from other home where they did great.
    There good size and I haven’t cut them back threw winter because I’m afraid of losing them.
    Any thoughts ? Thank you for your time. Maureen

  2. Kathy Green says:

    Hello, I have a problem with Monarda. I grow it for pollinators and it’s beautiful. But, it’s always covered with mildew! Could you please give me a name of a variety that you know will stand tall and not mildew?? I grow it in sun and part shade.
    Thanks, Kathy

  3. Linda Blandy says:

    I have about 40 day lilies. A lot of them are Stella Dora lilies. For the past few years, the lower leaves have browned. The blooms have gotten less. Last year I split several of them hoping that would revive them. This year I realized they had aphids and had to resort to “Seven” which I hated to do. Some of my other day lilies have deformed buds.
    All my day lilies were purchased at a local day lily farm about fifteen years ago and have always been outstanding. Are they just tired, or maybe I need to fertilize? I want my gardens to look lush. I am not one to constantly water because I’m on a meter. I am willing to do what you think is best.

  4. Ruth Rogers Clausen says:

    Hi Maureen,
    It sounds as if your hydrangeas are not liking the full sun position. I wonder if they were in more shade in the previous house? Hydrangeas are best in part shade with plenty of water (hydra=water, as in hydrate). Prune the plants immediately after bloom time as then they grow new stems that will bear flowers to following year. You should expect more than a single bloom of course. Perhaps the buds are being blasted by winter storms. You don’t say which zone you are in. Putting them in more shade would provide a little protection also.

  5. Ruth Rogers Clausen says:

    Hi Kathy,
    I am also a fan of Monarda or beebalm. Mildew is an ongoing problem but look for light pink Monarda bradburiana, the Eastern beebalm that remains mildew- free. Otherwise clear pink ‘Marshall’s Delight’ may be the most resistant, although petite dark cherry ‘Pardon my Cerise’ and others in the Pardon Me series are recommended as resistant as well. All are best in sun, with adequate moisture and plenty of air movement. Edit the older stems if plants become thick.

  6. Ruth Rogers Clausen says:

    Hi Linda,
    As low maintenance as daylilies ordinarily are, they do not appreciate NO CARE! If they were planted 15 years ago, undoubtedly they need a renewal. Overcrowding will encourage leaf decline and make the plants susceptible to pests and diseases. I suggest lifting and splitting the healthiest plants for replanting, and discarding the rest in the trash (you don’t need aphids etc. in your compost pile). After this is done, preferably this fall before frost, water thoroughly and apply a nice organic mulch to help retain soil moisture. If you can manage it, in spite of the water meter, apply about 1″ of water weekly next summer and going forward when it is hot. A 1″-2″ mulch of compost, shredded leaves, or fine bark is effective to keep weeds down as well. A planting 15 years old is pretty remarkable. It has served you well!

  7. Mary Ellen Krober says:

    I have a number of perennials that look as if they need to be divided but I can’t seem to find out when is the best time of year to do the dividing and also whether the answer to this question depends on the species. Can you direct me to a good source for this information?
    Thanks!

  8. phyllis erhard says:

    I am having trouble with my white breech tree the leaves in the center of the tree looks as if they have been burned.

  9. Carole Bayer says:

    Dear Ruth,
    How do I get rid of mugwort in my flower garden?
    It is unbelievable and everywhere
    Thanks
    Carole.

  10. Ruth Rogers Clausen says:

    HI Mary Ellen,
    Tracy DiSabato-Aust has recently revised and expanded her excellent book: “The Well-Tended Perennial Garden” (Timber Press). It is filled with good advice and there is a short chapter on division (p79). You will see that different species respond best to fall or spring division, but at the end of the day most are not that fussy. If you live where winter comes early or stays late that will influence your decision. Hope this is helpful

  11. Ruth Rogers Clausen says:

    Hi Phyllis,
    There are several diseases and pests that have been causing trouble with beeches in recent years. I do not have a photograph or know where you are located, so it is impossible for me to give you definitive advice. I suggest you take a picture to your local expert tree company or to the Cooperative Extension office in your state. Either may even be willing to arrange for a consultation or site visit at your home. Good luck with this.

  12. Ruth Rogers Clausen says:

    Oh Carole, you are not alone if that is encouraging!
    Mugwort (Artemisia vulgaris) is a serious perennial weed that spreads by underground roots or rhizomes as well as by seed. In the short term and on a small scale, dig or pull the plants and get as much of the underground parts as possible. On a larger and longer lasting scale: 1. Cut the plants down as short as possible. 2. Cover the area with a thick layer of corrugated cardboard, clean newsprint, or a tarp. 3. Top with a 3-4″ layer of mulch. Leave this for at least a year before pulling away the mulch and removing the remains of the cardboard. It will be easier to dig out any remaining roots that have not been suffocated. Be vigilant about young shoots and remove immediately. Hope this works for you.

  13. Sue Haugh says:

    Hi Ruth, I have dug out some bearded iris. They have traveled with me to different locations- some are 40 plus in age living now in Rochester, NY. They have been in a flower bed with other perenials. The beds get mulched in the Spring. When I replant do they need to be planted in a mound above the mulch or do I let the mulch continue to cover them. Thanks for any help you can provide.

  14. Carmelita Britton says:

    Dear Ruth –
    I had pretty good luck with my tomato plants this year, potted in containers with “new” potting material because of previous problems with my garden soil. However I had a new problem this year, with black, powdery growth (fungus?) on the stems, starting from the main stem and including some branches. The fruit seemed unaffected by this scourge, though the plants began to die off prematurely. I placed all the plants in plastic garbage bags to dispose of them, but I’m sure spores blew around the garden. Any thoughts about the nature of this infection, when it came from, or what I should expect next year?

  15. Hi Ruth,
    I have several roses that were planted in my garden by the previous owners. They seem to be old, big long canes with viscous thorns. Beautiful “day” roses clustered, pink with sweet fragrance. I know nothing about roses, but understand they badly need pruning. What is the best way to tackle this? How deeply should I prune these lovely old ladies. I’d hate to lose them.

  16. Ruth Rogers Clausen says:

    Hi Sue,
    Bearded iris roots (fat rhizomes) do not like to be covered with mulch. The tops of the roots do best when they are exposed and baked by the sun. Plant about 1/2 the horizontal depth and don’t cover them with soil or mulch. Water them in gently to get them settled. Hope they do well in your new garden.

  17. Ruth Rogers Clausen says:

    Hi Carmelita,
    It sounds as if your plants have been attacked by aphids or other sucking insects that have left sweet “honeydew” deposits on the foliage. This attracts the growth of black sooty mold fungus that covers the leaves, interrupting photosynthesis. As time goes on the leaves brown and die, although the fruits may not be attacked. Next year keep a sharp eye out for aphids especially on the growing tips of the plants. Treat these as soon as they appear, before there is an infestation.

  18. Ruth Rogers Clausen says:

    Hi Therese,
    How lovely to inherit some nice old roses, even if they do have vicious thorns!. You can cut out any dead or damaged canes now, to the ground. But at this point I would be inclined to cut the long ones or tie them in so that they don’t get broken in the winter winds. Next spring, about when the forsythia or other spring-blooming shrubs burst into bloom, thin out the canes to the base, leaving the strongest. These should be cut by about 1/3 to 1/2 their length, to an outfacing bud. Use sharp hand pruners, and make a slanting downwards cut, so that rain will fall away from the dormant bud. I think you will be happy with the results. The new growth should produce a nice crop of blooms.

  19. Ruth Rogers Clausen says:

    Therese,
    I neglected to remind you that the leather gauntlet gloves from Womanswork are especially made for rose pruning. They will protect your arms from even the most thorny shrubs. I wouldn’t attempt to prune without them and have give many pairs as gifts to my rose-loving friends! The Holidays are coming!

  20. Thanks for the advice. I am off to get my pruning shears right now!

  21. Bayla Singer says:

    I live in Florida, in zone 10. I’m confused about what plants might grow well here; if something is hardy to zone 9 or 8, would it be ok in 10? How can I find out about plants’ preferences for short or long day length, resistance to heat, etc?

  22. i live in coastal san diego county…. climate zone 10 ….or 24 in sunset western garden book……most of my plants thrive under my thumb……cannot get a clivic to bloom and actually lost a yellow one…..the orange non bloomer is in the ground on the north side of my home thanks

  23. Ruth Rogers Clausen says:

    Hi Bayla,
    You should have the opportunity to grow lots of tropicals and subtropical plants in your zone 10 garden. If a plant is marked for Z8 or 9 it should do fine for you as well. The zone marking denotes the lowest or coldest zone where it will survive, but these are really just guides. There are a couple of good on line sites:http://www.south-florida-plant-guide.com/; http://www.fairchildgarden.org/Home-Gardening. There are numerous books available as well, probably some at your local library. The Complete Guide to Florida Gardening
    by Stan DeFreitas is a good reference. Enjoy!

  24. Cecile Lowrey says:

    We have a large very old, probably planted when house was built in 1950, Concord grape vine. We have been getting 100 lbs. of grapes a year, just cutting it back some as we are picking, but we would like to know how we are properly supposed to care for it and prune it. Thank you. Salem, Oregon It grows up the garage walls on the East and South walls.

  25. Ruth Rogers Clausen says:

    Hi Nancy,
    I am sorry for the delay in answering your query, and that you lost your lovely yellow Clivia. I don’t know how old the non-blooming one is, but at least it is in a good place on the north side of your house. Try to give it a rest period in fall into winter if you can, withholding water and fertilizer for a couple of months. In containers the plants require more irrigation as they dry out more quickly than in the ground. Hope this will be helpful, but if the plant is young you may have to wait a couple more years for it to mature.

  26. Ruth Rogers Clausen says:

    Hi Cecile,
    How fortunate to have inherited an established Concord grape vine. Obviously the treatment that you are giving it is working well. Grapes are mostly produced on shoots made the previous season. Shoots are “spurred back” to a couple of buds or “eyes” in late winter before the sap rises. Remove some very old stems or canes annually so the plants do not become overburdened. However if you prune too hard, you will get an abundance of new shoots that will not produce fruit until the following year. Enjoy your crop.

  27. Jody Block says:

    Dear Ruth, I have a stand of 7 fully grown Miscanthus sinensis ‘Morning Light’ that is about 4 years old. Every year up till now they have stood beautifully all winter. This year, however, they keep falling down after every rainstorm, starting in October. I am tying them up but this detracts from their pretty, carefree appearance. What do you think I have done wrong? I garden in Louisville, Kentucky.

  28. Ruth Rogers Clausen says:

    Hi Jody,

    Miscanthus ‘Morning Light are beautiful when they remain upright. However flopping all over is not so attractive. Could your plants have gotten irrigated too much this hot summer? These grasses tolerate drought well and if overwatered and/or over-fertilized will produce soft, sappy stems that flop over with heavy rain. You’ll find they are more attractive if supported with heavy twigs or brush instead of tying them up. When you cut them back in the late winter, leave a foot or so of the old stems to help support the new stems coming up through them. Hope this is helpful.

  29. Thanks Ruth. I will watch the watering next summer.

  30. cindy frank says:

    HI Ruth, I have moved my fig tree into the garage for the winter. the leaves have not dropped yet. should i be watering it at all ? any tips on keeping it alive for the winter? I live on Cape Cod (zone 7)

  31. Margaret (Penny) Haines says:

    Holiday Greetings, Ruth. I am back again with a question re. my Hydgrangia. They had NO blooms this year. One barely grew, the other is a beautiful bush but no blooms. My lace Hydgrangia, Pinky Winky, Snowball bush and Laurel, all in the same area, had a healthy, wholesome summer and fall.

    I appreciate you advice with advance thanks.

  32. Ruth Rogers Clausen says:

    Hi Cindy,
    I hope you got a good crop of figs this year. Several friends here (also Z7) had amazing crops. Actually figs should overwinter safely out of doors in Z7. However, if you prefer to have them indoors they are not hard to overwinter. You can pull back on water now and just keep the soil very slightly damp for the next few months. The remaining leaves will drop quite quickly, but don’t allow the plants to become desiccated. Keep the plant in a dark place above 30? but below 50?. I hope you don’t have mice in the garage? They will have a winter feast on its stems, so be sure to protect the plant. Good luck and Happy Thanksgiving!

  33. Debi Balog says:

    I experienced a major infestation of white flies in my garden this summer spreading throughout my property. Will the colder winter weather eliminate them for next year or what prevention should I take next year to avoid the mess?

  34. Sheila Bowden says:

    For the past 3-4 years, I’ve had trouble with mealybugs in some pots of annuals and tropicals I grow on my patio. I’ve never had this problem before and I’ve been gardening a long time. I’ve disposed of the plants and soil in them (in the garbage) in hopes of getting rid of them. And somehow they reappear. I use neem oil and granular rose care to keep them in check as much as possible but I’d really like to get rid of them completely. Is it possible ? I garden in central Mississippi, zone 8.

  35. Ruth Rogers Clausen says:

    Hi Debi,
    I’m afraid that your infestation of whiteflies will not be eliminated during cold weather this winter, although they will be slowed down a little. Next spring keep a look out for eggs and nymphs and apply Neem or something similar. It is critical to stop a pest infestation from the start. Remove any dead leaves regularly, spray the plants with water to knock off the flies, and consider importing beneficial insects to your garden. There are several beneficial insects such as brown lacewings that prey on whiteflies. Check on line for these. As whitefies are attracted to the color yellow, many people find they can control the pests by attaching sticky yellow cards on posts round the crop. This works well in greenhouses as well. Unfortunately, whitefles are a perennial problem, and your best plan is to control rather than try to eliminate them.

  36. Ruth Rogers Clausen says:

    Hi Sheila,
    Mealybugs are another ongoing pest (see above) that can be a real problem in some gardens. You did the right thing to destroy affected plants and their soil. It is doubtful however that the problem will go away completely. As mealy bugs begin to appear in spring inspect the plants routinely and destroy whatever bugs show up. With houseplants, I use a cotton swab dipped in rubbing alcohol on a daily basis to avoid build up. Rub off any eggs that you can identify and remove badly infected leaves. Neem oil and insecticidal soaps are good products to use against mealy bugs. Be sure that you do not overwater or overfeed your plants–bugs are attracted to soft, lush growth. Try beneficial insects such as ladybugs and lacewings as well. I hope you cleaned up the surrounding area thoroughly after the growing season–you don’t want overwintering pests hiding in crevices in the soil waiting for spring to arrive. As a precaution, inspect any new plants bought in for the summer from nurseries and garden centers. Sometimes pests hitch-hike into your garden.

  37. Ruth Rogers Clausen says:

    Hi Margaret,
    Sorry to miss your question before. Glad your ‘Pinky Winky’ and others did well. They are cultivars of Hydrangea paniculata that blooms on stems that grew this past summer, and should be pruned in spring. The ones that did not bloom however, are probably H. macrophylla varieties, that set their buds the previous season just after bloom time. If you cut them last fall or this past spring to tidy them up you would have cut off any latent buds for the season just passed— Plenty of foliage but no flowers. I suggest you don’t prune those for a couple of years to get in the rhythm of their bloom schedule. Happy Holidays

  38. Margaret (Penny) Haines says:

    Thank you, Ruth, Merry Christmas and a healthy New Year filled with love and contentment. cares ‘n prayers from Penny

  39. Ruth Rogers Clausen says:

    Thanks Penny. Same to you and all the others who have written to me this past year on the Womanswork page. I look forward to a bright and shiny 2018 for us all.

  40. Maureen Arnold says:

    I have a Christmas cactus that is a little over a year old and it has been dropping branches for over a month. In fact, one of the plants has dropped everything and is just a stump in the pot. It did not bloom for Christmas as I did not do the light control process. The plants in the pot seem healthy so I don’t understand why the branches are falling off. I am trying to start some of these branches in a separate pot. It gets sunlight through a southeast-facing window, plus I keep the lights on most of the time. Once a month I soak it in a big bowl full of water for an hour, then give it light watering in between. Sometimes I use ice cubes so it gets a slow drink. Any help would be appreciated, including tips on how to get the fallen branches to propagate.
    Maureen

  41. Ruth Rogers Clausen says:

    Hi Maureen,
    Sorry about your problem Christmas cactus (Schlumbergera spp.). Although usually these plants are not difficult to grow, there are certain conditions that they require. Overwatering is a common problem, and coupled with soil that does not drain freely, it can be fatal. Although your watering regime may not seem like much, I think indeed the plant is not getting a chance to dry out between waterings. Consider repotting the remaining plant into a clean pot (with a drainage hole) with 1part “container soil”: 1part coarse sand or chicken grit. Healthy pieces can be rooted in perlite or vermiculite mixed with coarse sand or chicken grit. Personally I have not been successful trying to root in water.

  42. Maureen Arnold says:

    Thank you so much, Ruth, for your information and advice on how to get my Christmas Cactus back to a healthy state. I have to admit that I am not a plant person; I can even kill plants that I have been given and told can’t be killed. LOL. I will keep trying and I really appreciate your help.
    Maureen

  43. Sharyn Moorer says:

    Dear Ruth,
    Can hosta be separated in the Spring?? Sharyn

  44. Ruth Rogers Clausen says:

    Hi Sharyn,
    I have not had success with trying to split Christmas cactus.. Often the base of an older plant is woody and does not appreciate being broken apart. I find it is better to take cuttings and root them separately. However, you may find 2 or 3 individual plants in a quite small pot and these break apart readily. Good luck with them.

  45. Louise Veffer says:

    How do you get rid of lily of the valley and wild pansies,I mean the easy way.

  46. MONA SCHNITZLER says:

    I live in Brooklyn, NY and have been trying to grow a fig tree for years. The fig in question, Chicago Hardy, seems to be right for my zone. It’s planted in a large container, mulched, and covered in the winter. The current one came back last spring, but this spring, it is quite gone. I don’t have the room to plant one in the ground. Any suggestions would be much appreciated.

  47. Margaret (Penny) Haines says:

    Dear Ruth, I am truly perplexed about my Rhododendruns. They are approx. 45 yrs. old. The lower growth is healthy but the upper branches and leaves are scraggly and spotted. I have fertilized them, put pine needles around them, and am now spreading coffee grounds around the soil. Please help, I am confident you have some answers. They do produce a few blossoms, nothing like they used to be. I wonder if I should trim them down to the new growth?? I offer my advanced thanks for your service.

  48. Ruth Rogers Clausen says:

    Hi Louise, many of your fellow gardeners would be thrilled to have your lily-of-the-valley problem. Not sure about an “easy” way to get rid of them, unless you really want to poison them and the surrounding soil. You don’t say where you live or how enormous the offending patch is. You might want to hire some strong person to dig the roots out for you. They spread by underground horizontal stems (or rhizomes) and thus can be more than a little assertive! I’m sure some of your neighbors or fellow garden clubbers (you do belong to a garden club of fellow garden enthusiasts don’t you?) would be glad to have plants from you. Wild pansies are best pulled out, including the roots… before they go to seed. Did you know the flowers are edible? My daughter’s wedding cake was decorated with sugared wild pansy flowers and it looked amazing! Good luck!

  49. Ruth Rogers Clausen says:

    Hi Mona, I know only too well about losing fig trees over the winter. Yes ‘Chicago Hardy’ should be fine in most Brooklyn winters. I thought mine would be fine here on the Eastern shore also and we are milder than you are. My suggestion is to bring the pots indoors (an unheated garage or basement works) over the winter and return the pots outside as it starts to warm up. I am of the opinion that often it is not only the cold weather that does them in. Excellent drainage is essential–you don’t tell me how the soil and drainage is. Make sure it drains freely so the roots don’t sit in wet soil during bad weather any time. Wind is another variable that you can control. Perhaps you can find a spot in the garage over the winter and just check from time to time in case of drying out. After the leaves drop they don’t need light. I hope we both make out better next year!

  50. Ruth Rogers Clausen says:

    Sharyn, I believe I neglected to reply to your winter message. I do apologize. Yes, spring is a perfect time to divide hostas, as soon as you can see some new growth. Depending upon where you live, the leaves may be fairly large by this time, so be careful not to damage them if possible. Dig around the plant away from the center or crown, lifting it slightly to loosen the roots. You can either divide it while it is still in the ground, or lift it completely and them split it with a sharp spade thrust down it’s middle. If you move the leaves apart prior to cutting it makes it easier to see a good spot to cut. You might want to make several new plants from a single one, but beware of making the pieces too small as they may take at least a season to become established.

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