I'm thinking of writing more on this, but for now, consider the black petunia. Called 'Black Velvet,' it came on the market in 2011 to generally favorable reviews. Growers loved it, but there was some hesitation, too. Black - far as I know - has never been a popular color in the garden, and some folks hesitated. But this petunia really is cool.

I found it at Terrain at Styers in Chadds Ford the other day, along with 'Phantom,' another black petunia with a cream/yellow star in the center. There's at least one other black petunia - 'Pinstripe' - and a few other darkly dark flowers out there, among them hollyhocks and pansies.

This picture shows why the experts are forever emphasizing the idea of multi-season "interest," that something ought to be happening in every season in the garden. These so-called bridal wreath spireas line 16th Street near Vine and do they look pooped or what? These shrubs are old-fashioned favorites, but I've never seen the appeal - beyond about a week in spring, that is. For that brief moment, they're spectacular. Then ... they turn brown, a slow death, like this one, and that's it, folks. We're stuck with an unruly, brown and green blob for the rest of spring, and all of summer and fall. (And, oh yeah, it stinks.)

Nothing else in this bed, which is why I thought of the "interest" thing. It's a simple concept that, oddly, is really hard for gardeners to figure out: Plant stuff that blooms or colors up or has an interesting feature (bark, foliage, flowers) in every season. When I interview expert gardeners at home, they all have something going on out there, even in deepest winter. Winter jasmine, or red twig or yellow twig dogwood, or witch hazel.

Like everything else this crazy spring, roses are early. Way early. Frankly, this couldn't happen at a better time; times are tough all around, and it seems everyone you meet is depressed over something! My pink double Knock Outs are blooming with abandon, and while you can argue with this blockbuster's lack of fragrance and bemoan its ubiquity, you can't (seriously) knock it - it's reliable, it's not bad looking, and it grows no matter what you do or don't do to it. It fills in inconvenient gaps in the landscape.

Somehow, though, Knock Out doesn't provide the lift - the thrill - that some other, more unusual, roses do. Maybe it's because it's like wallpaper these days. Everywhere you turn, there's a lonely Knock Out in the middle of a weedy bed in front of McDonald's or the bank.

Look at this stuff! Chives make any flower garden pop. Saw these in the Idea Garden at Longwood yesterday. Big clumps anchored the four corners of almost every bed in the herb garden there and let me tell you, on a chilly, gray day, they were standouts. Lately, it seems, everyone's into herbs for their ornamental value, which for chives is considerable. What part of your garden wouldn't be enhanced by a show like this?

Chives are useful in many ways, too.  You can eat both flowers and leaves, usually in salads. Both also can be sprinkled atop or around a plate for dramatic effect. Chives are very high in vitamin C, and were used in herbal medicine to help with digestion. They were put to other uses, too, but I'll spare you the details. One wonders how the ancient herbsters ever came up with some of these things. Let's see. You have hemorrhoids? Ah yes, let's try leeks for that. (Wait - I promised not to go there.)

Looked all over the internet and found almost nothing on Dr. Ruppel, the hybridizer of this fabulous clematis. All I could find was "Argentina, 1973." Regardless. It's a lovely spring (and late summer) bloomer that popped open on my black fence this past week and caused spontaneous happiness among dog-walkers. This one came from the Morris Arboretum plant sale, which, if you haven't been to it, is one not to miss. It's May 12 this year (for the public).

To digress: This is plant sale season, and there are wonderful places to buy. Check out Eva Monheim's column this Friday (called It's Time To ...) in the Home & Design section. She has suggestions for what and where to buy, but for a good roundup of sales at public gardens in the area, go to greaterphiladelphiagardens.org; they've compiled a roundup. After going to a lot of these, I think I'll never again buy plants at box stores - if I can help it. Local garden centers and area plant sales are the way to go.

It goes something like this: ornamentals plus edibles. Big trend, and nowhere have I seen it done better than at the PHS' City Harvest exhibit at the flower show. I blogged about it then, and was moved to do it one again after a colleague recently asked PHS, and then received by email, the plant list for that exhibit. It's quite a long list for the whole exhibit, which also included the lettuce wall, the vegetable/community garden, the fragrant wall, not practical for the home gardener - or, at least, anyone without "help."

But it you're interested only in what's shown here, what was called the celebration garden, a mix of edibles and ornamentals, I can give you the plant names. There are only 18: alyssum ('Snow Crystals'), basil (Genovese), calendula (Kablouna mix), cardoon, celosia ('New Look Yellow'), cilantro, cleome (Queen Mix), cosmos (Sonata mix), dill ('Bouquet'), kale (dwarf blue curled), rosemary, purple sage, stachys ('Helene von Stein'), sunflower ('Firecracker'), verbena bonariensis, and zinnia ('Persian Carpet,' 'Gift' and 'Red Cap').

Here's urban farmer Annie Preston, wearing sunglasses after being stung by a bee on Monday, weeding at the Urban Tree Connection's farm at 53d and Wyalusing. You can certainly see the urban nature of this spot, and just imagine its former lives as garage, a storage area and, according to one oldtimer in the neighborhood, a plant nursery. Must've been a long, long time ago! Finally there was a fire and then blight set in. Neighbors recall all sorts of unsavory stuff going on in there.

Today, the place is quite savory, I can assure you, in both the cultural and culinary senses of the word. Yesterday Annie was pulling grass and lamb's quarters, an irritating weed that chefs now use in salads and other dishes, from the rows of spring onions. The weeds this year - as you may have seen in your own garden - are plentiful. I'm on the third or fourth round of pulling in mine ...

This is Annie Preston, who's chosen "urban farmer" as her current and future profession. She helps manage a 3/4-acre organic farm at 53d and Wyalusing, in the Haddington section of West Philly, that's surrounded - you might say protected - by rowhouses. It's an interesting place, one that I'll be visiting again tomorrow to talk to Annie again and to check on the progress of the crops - radishes, chard, spinach, carrots - Annie gave me this one - potatoes, garlic, onions, collards, kale, spring onions, beets, green beans ... and the list goes on.

There's one bee hive, and a desire to harvest and sell honey, a tidy composting operation, kids' programming, a farmer's market, cooking classes, and a healthy network of neighbors and volunteers helping out. It's all done under the auspices of the Urban Tree Network.

Our native redbud is getting more popular, thanks to the tree-planting programs so active in the city and region. Salutes to them, really. They are making such a difference. I'm seeing redbuds and other great street trees all over my neighborhood and others in my travels. Not so many Bradford pears anymore, though they were the rage in the '80s.

Bradford pears, which are nonnative, turned out to be problematic on several fronts, including the fact that at a certain point, they start falling apart. They have "weak wood." And they're susceptible to disease, although they're not the only street tree this is true of. They are pretty in spring, no question, and remain an extremely popular tree for roadsides, homes and municipalities.