Getting Garden Mums to Flower

Q. I planted some mums last year and they were beautiful. They came back this year and are growing wonderfully, and look fantastic. My question: I’ve been told that they will blossom in early summer and then again in the fall and that if I snip off the buds in the early flowering, then the fall flowering will be even better. What do you say about flowering mums?
-Chesapeake, Virginia

A. Sometimes, mums are sold in the spring with buds so that the customer can see what color the flowers will be, but fall flowering mums do not bloom in early summer. Depending on the variety, they can start blooming any time from August on. Some of the older varieties, my favorites, do not even begin to bloom until October. Again, depending on the variety, mums can vary in height from twelve inches to twenty-four, even thirty-six inches tall. The problem with the taller ones is that they tend to flop. For these, I suggest cutting them in half once they are eighteen inches high. This will make them shorter and bushier.

-Bobbie Schwartz
Bobbie’s Green Thumb
Shaker Heights, Ohio

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Wisteria Not Blooming

Q. I have several wisteria plants that are probably offshoots of a main vine. The main vine blossoms like crazy every year but the offshoot plants don’t blossom, even though they grow and send out lots of stringers and look very healthy. I want to train and control these off shoot plants and want them to blossom. What do I need to do to get them to blossom?
-Chesapeake, Virginia

A. Some wisteria don’t bloom until they reach a certain point of maturity. Sometimes, laying off the fertilizer for a year helps, too, as it doesn’t promote so much green growth (versus flowering activity).
Denny Blew, BlewLabel Perennials
Bridgeton, New Jersey

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Dehydrated Wisteria in NYC

Q. I have a beautiful wisteria on my terrace. It was green and leafy. I have an irrigation system as well as someone to check them when I am away. I just returned from a 6-day vacation and upon return my wisteria did not get enough water (the irrigation hose slipped out of the planter and my friend didn’t notice). It is not dead but most of the leaves are brittle and some are burnt on the edges. I watered it and put the hose back in. What are its prospects? Anything else I can do to help it along? Not sure what kind of wisteria and it is in a large planter. I was told they are hearty but anything that needs water and doesn’t get it has problems.
Manhattan, New York

A. Wisteria is a very hardy and tough. Some of those leaves that have burned and curled will likely fall off. But with continued watering (and water soluble fertilizer once a week) and our good weather in New York, you should (I expect) get a second flush of leaves. This same drying issue happens to Spireas, Potentillas, and Dappled Willows, as well, and the plants rebound very nicely.

Todd A. Efing,
Van Putte Gardens
Rochester, New York

www.vanputte.com


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Gaillardia Not Growing

Q. I planted gallon pots of Gaillardia last year. I don’t see any of them coming up this spring. Perhaps I’m mistaking them for weeds? What should they look like by this time?
-Geneva, Illinois

A. Gaillardia needs excellent drainage to survive wet soil during the winter. If you planted in heavy clay, I am not surprised that they died.
-Bobbie Schwartz
Bobbie’s Green Thumb
Shaker Heights, Ohio

A. Gaillardia needs the right conditions to overwinter. They are native to the midwest plains and want a neglected condition: low nutrients, no overabundance of water, and so on. They have sort of a dull, fuzzy, longish leaf.
-Denny Blew, BlewLabel Perennials
Bridgeton, New Jersey

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Identifying Trachelospermum jasminoides

Q. We recently moved to South Carolina and this house. I think we have a honeysuckle bush growing along/up our fence. It doesn’t match up to what I am finding online. I am not sure I have smelled honeysuckle before, but this is wonderful and I assumed this is what it was. I think the leaves definitely look the same and the flower petals for the most part, but what we have doesn’t have the stamens that I am seeing in online photos.
-Aiken, South Carolina

honeysuckle-bush

A. Thanks for including the photos of your plant-in-question. After a search through the landscape plant manual to confirm, it appears you have a lovely, vigorous Trachelospermum jasminoides (Star Jasmine or Trader’s Compass). Here is another great online reference for you to take a look at to learn more about your hardy, easy-to-care-for beauty: http://hort.ufl.edu/shrubs/TRAJASA.PDF. Trachelospermum jasminoides are fairly low maintenance (lucky you!) and have a blossom so fragrant they are used to create perfumes.

Our next door neighbor actually has one of these and one warm nights the scent is wonderful coming over the fence. Enjoy!

Shannon Mullett-Bowlsby, co-founder, owner
The Lazy Locavores & King County Master Gardener
Seattle, Washington

Follow-Up Q. Thank you so much for your response! Do you know if I can take a cutting & plant it in other areas?

A. Yes, it’s a non-patented plant, so there are no legal issues, and it should propagate easily. I’d take three cuttings about 6-in. long, strip the bottom-most leaves, dip the cuttings in rooting hormone (you can get this at a garden center). Stick it about I-in. deep in wet potting mix in a container, cover loosely with a baggie and place in indirect light. They should take root in a couple of months. On the other hand, you can probably buy small already-started plants for not too much money. Good luck.
-Denny Blew, CenterPeace Plants
Bridgeton, New Jersey

A. Yes, it actually should root very easily with some rooting hormone. I’ve even rooted it in water. May is the best month to take cuttings. They need to be semi-hardwood, which means growth that hasn’t hardened off yet like the old wood, but isn’t green and flexible either. I’d take about 6-in. cuttings, and stick into a 1/2 peat moss and 1/2 perlite mixture, or just plain old SC sand would be fine as well. I actually had a “rooting bed” in my backyard that was nothing but plain old sand, and it rooted things very well.

You can also “ground layer” them, by scraping the underside of pieces running on the ground, and putting a brick or rock on top of them. They will form roots in the ground, and you can later cut them off and dig them up to transplant. You can also pin pieces to pots with bent wire (I use old wire coat hangers, cut and bent into “u” shapes like hairpins.).

Deborah Aldridge, horticulturist
North Port, Florida

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Powdery Mildew on Snap Peas

Q. It’s nearing the end of sugar snap pea season here in Sacramento. A bunch of my plants, while still producing a few peas, are covered with what appears to be a mildew or mold that turns the leaves and stems white (powdery). Some of the pea pods themselves are mottled on the sun side with black spots (mold?). I’m wondering if it’s still safe to eat them. Seems strange to have fungus when the air has been real dry. Thanks in advance.
-Sacramento, California

A. The problem you are having on the peas is called powdery mildew. I don’t think I would eat them. Time to pull them out and plant some beans. The reason you have powdery mildew on the peas could be from watering the plants in the evening. If the leaves are wet at night, powdery mildew will grow even if the days are dry. Always water early in the morning. This will allow the leaves on all of your plants to dry off before night time.
Tim Lamprey, Harbor Garden Center
Salisbury, Massachusetts

A. Powdery mildew will grow any time temperatures are between 60-80F and the light conditions are less than stellar. It does not need a lot of free moisture. As to the safety of the fruits, I do not know. Next year, look for mildew resistant varieties, or run a spray program that prevents fungus.

-Denny Blew, CenterPeace Plants
Bridgeton, New Jersey

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Planting Under Black Walnut Trees

Q. Any suggestions as to what to plant beneath a Black Walnut tree? I have tried rhododendrons without luck. I like the tree, carefully pick up the fruit when it falls to no avail. What plants if any will grow around a ‘Juglan’?
-Hudson, Ohio

A. There are a number of wildflowers and native grasses that will grow beautifully under Black Walnut trees. Black Eyed Susans, Cardinal Flowers, Jack in the Pulpit, Wild Senna, Prairie Smoke, Sneezeweed, Sunflowers(perennial), Great Blue Lobelia, Mountain Mint, Goldenrods, Ironweeds and Asters. In addition, two gorgeous shade grasses—Northern Sea Oats and Fine Fescue Grasses will do just fine.
-Miriam Goldberger, Wildflower Farm
Ontario, Canada

Here’s some additional information from another gardening professional:

A. Planting around Black Walnut trees is a problem because the tree produces a substance called juglone, which negatively affects other plants. One of my coworkers at About.com has written a nice article about plants that are especially sensitive to juglone, as well as a link to a list of juglone-tolerant plants. I hope you can find the right one for your yard!
http://gardening.about.com/od/gardenproblems/qt/Black_Walnuts.htm

Here’s my profile about Black Walnut trees. http://treesandshrubs.about.com/od/commontrees/p/blackwalnut.htm

Vanessa Richins
Guide to Trees and Shrubs
About.com
Twitter: http://twitter.com/treesandshrubs

And another!
A. Many plants will grow under Black Walnut but not Rhododendron. Try some of the following:
Ajuga reptans (Bugleweed), Asarum europaeum (European Ginger), Galium odoratum (Sweet Woodruff), Geranium sanguineum (Cranesbill) if it’s too shady, most ornamental grasses, Hosta, Pulmonaria (Lungwort), and Stachys byzantina (Lamb’s Ear) but I recommend one of the non-flowering cultivars assuming that it is sunny.
–Bobbie Schwartz, Bobbie’s Green Thumb
Shaker Heights, Ohio

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Growing Conditions for Spiderwort

Two answers for this one!

Q. I purchased a Sweet Kate Spiderwort and I am not sure how much sun or shade this plant needs?
-Huntingdon Valley, Pennsylvania

A. Sweet Kate Spiderwort is one of the most visually vivid partial-sun plants around. It does best in morning to early afternoon sun (1pm-2pm). The bright yellow foliage will sometimes get sun scorched in hot afternoon sun locations. You can plant this perennial in a mostly shade area, but be aware that the foliage will become more chartreuse and the vivid purple flowers will not be as plentiful.

-Todd A. Efing, 
Van Putte Gardens

Rochester, New York

A. I think you will love ‘Sweet Kate’ I have been growing her for several years on the east side of my house where she gets a couple of hours of sun in the morning but nothing much else. She blooms very well and the yellow foliage is lovely too. I planted a skirt of Lysimachia nummularia ‘Aurea’ (Golden creeping Jenny) around and it looks great. If you put spiderwort in full sun I find that it tends to burn later in the season when it gets hot. I am in NY Zone 6, so our conditions are similar.
-Ruth Rogers Clausen, Garden Writer
New York

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Pruning Forsythia

Q. I cut my forsythia back completely last spring, to about 3 to 4 inches in height. Over the course of last summer it grew into a nice looking shrub. This spring it is too leggy. Each branch is a good 36 to 46 inches and hanging low. The bush cannot be mowed around for the drooping branches. Is there a solution to begin shaping this shrub, or should I resign and dig it up completely.
-Washington, Indiana

A. As you have found, Forsythia are very strong willed and can rebound strong after a hard pruning. You had so much length growth due to the existing large amount of roots using all the stored sugars on a small amount of stems.

At this point lightly prune the forsythia back into some shape. By a little, I mean just prune enough back to take some of the weight off (no more than 8 to 12 inches). Next year you will likely see long growth again, but not as radical. At that point just simply prune to maintain at the 6 to 10 ft. size.

You have created a pruning project each year now due to the radical prune last year. If the Forsythia is too big for the space, then it might be best to remove it. Otherwise, simply enjoy it and don’t become over active with the pruners.

-Todd A. Efing, 
Van Putte Gardens

Rochester, New York

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Pruning Pampas Grass in Spring

Q. I have 3 large clumps of Pampas grass. They took a big hit this winter. They seem to be coming back along the outside perimeter, but the center is brown and dead. Should I cut the center back to nothing?
-Bellingham, Washington

A. Many grasses die out in the center but continue to produce new growth on the edges. You can leave it as is or you can undertake the difficult job of digging out the center. Most grasses have very strong fibrous roots, a characteristic which usually necessitates the use of a mattock or a pick and someone with a great deal of strength.

-Bobbie Schwartz, Bobbie’s Green Thumb
Shaker Heights, Ohio

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