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Gardening Answers Knowledgebase

Search Results for: Annuals and biennials | Search the catalog for: Annuals and biennials


Plant Answer Line Question

Keywords: Annuals and biennials, Petroselinum, Herbs

Is Italian parsley a perennial or a biennial?

Answer:

The Sunset Western Garden Book says that parsley (Petroselinum species) is a biennial grown as an annual.

University of Arkansas Extension provides additional information on growing parsley, including the Italian variety, which is Petroselinum neapolitanum, and curly leaf parsley, Petroselinum crispum.

Date 2017-04-13
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Plant Answer Line Question

Keywords: Silene, Plant identification, Alpine and rock gardening, Annuals and biennials

I am having trouble growing Silene (do not know the species). It has magenta flowers with notched petals on two foot stems and hairy basal foliage. I have killed four plants that were planted in four different locations. I am able to keep hundreds of other plants alive in my garden, but not this one! It flowers profusely from mid April through July. Then the leaves start wilting, and before long, it is dead. The only thing I can think of is that it needs superior drainage. Could I be overwatering it?

Answer:

You may have one of the annual types of Silene, which die after setting seed. It is really hard to know for sure since there are over 500 species. You may be able to identify your Silene in the book Lychnis and Silene in the Garden, by J.L. Jones, 1999.

There are some magenta-colored species of Silene with notched petals (Silene dioica and Silene hookeri for example), as you describe. These are alpine or rock garden plants that prefer well-drained conditions and do not like highly acidic soil. It is certainly possible that you have overwatered or that the soil in which they are planted doesn't drain sharply enough or is too acidic.

Date 2017-05-30
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Plant Answer Line Question

Keywords: Annuals and biennials, Verbascum

I would like to know a little more about Verbascums. Are they a biennial? Will they reseed themselves? How long a period will they bloom. How tall can they become? Are they invasive? Thank you for you help! I have had very little experience with annuals and biennials.

Answer:

Verbascum includes 360 species, most of which are biennials, with a few annuals, perennials, and small shrubs, some of which are evergreen or semi-evergreen. The flowers grow on tall upright stems, and while individual flowers are shortlived, there are many of them and they bloom over a long period of time (summer into early fall, in most Seattle gardens).

In my own experience, they can reseed themselves, so if you would prefer not to have your plants do this, just cut off the tall stalk after the flowers have bloomed, and before they set seed. I checked the list of Washington State Noxious Weeds, and did not find Verbascum there, though it can be invasive in other parts of the country (Hawaii, for example).

If you would like information about specific varieties of Verbascum, the Royal Horticultural Society A-Z Encyclopedia of Garden Plants has photographs and descriptions of many of them.

Date 2017-04-13
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Plant Answer Line Question

Keywords: Annuals and biennials, Zinnia, Daisies, Verbena, Coreopsis, Artemisia, Salvia, Lavandula, Achillea, Echinacea, Xeriscaping, Tagetes, Sedum, Herbs, Container gardening

Our neighborhood has a small planter area at its entrance. There is no water supply to this area, but a nearby resident is willing to water occasionally. The soil contains much clay. We would like to plant a few drought-tolerant annuals to add color and supplement the more permanent shrubs--such as boxwood--planted in the area. Can you recommend some plant choices? How could we amend the soil to best hold water during the upcoming dry months? Would a commercial product such as "Quench" be of any value, in addition to organic mulches?

Answer:

I found the following article by Nikki Phipps on GardeningKnowHow.com about drought-tolerant container planting. Here is an excerpt:

"...many plants not only thrive in containers but will tolerate hot, dry conditions as well. Some of these include annuals like marigolds, zinnias, salvia, verbenas, and a variety of daisies. Numerous perennials can be used in a xeriscape container garden such as Artemisia, sedum, lavender, coreopsis, Shasta daisy, liatris, yarrow, coneflower and more. There is even room for herbs and vegetables in the xeriscape container garden. Try growing oregano, sage, rosemary, and thyme. Vegetables actually do quite well in containers, especially the dwarf or bush varieties. There are also numerous ornamental grasses and succulents that perform nicely in containers as well."

The Brooklyn Botanic Garden's book The Potted Garden (21st Century Gardening Series, 2001) provides a list of drought-tolerant plants for containers.

I had not heard of Quench, but since it is cornstarch-based, it is certainly preferable to the hydrogel and polymer products which are more widely available. I found an article by garden writer Ann Lovejoy in the Seattle P-I (June 3, 2006) about Quench. Here is an excerpt:

With pots and containers, mix dry Quench into the top 12 inches of potting soil in each pot and top off with plain compost. Few roots will penetrate deeper than a foot, so it isn't very useful down in the depths of really big pots unless you are combining shrubs and perennials.

I would not recommend hydrogels or polymers as a soil amendment. Professor Linda Chalker-Scott of Washington State University has written about these products and their potential hazards. Here is a link to a PDF.

You could consider applying a liquid fertilizer (diluted seaweed-fish emulsion would work) to your containers once every week or two during summer. Here is general information on container maintenance, from Ohio State University Extension. Excerpt:

"Once planted, watering will be your most frequent maintenance chore, especially if you are growing plants in clay containers. On hot, sunny days small containers may need watering twice. Water completely so that water drains through the drainage hole and runs off. Water early in the day.

"If you incorporated a slow release fertilizer into the potting mix, you may not need to fertilize the rest of the season; some of these fertilizers last up to nine months. You can also use a water-soluble fertilizer and apply it according to the label directions during the season.

"Mulch can be applied over the container mix to conserve moisture and moderate summer temperatures. Apply about one inch deep.

"Depending on the plants you are growing, you will need to deadhead and prune as needed through the season. Monitor frequently for pests such as spider mites. Pests usually build up rapidly in containers."

Date 2017-05-26
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Plant Answer Line Question

Keywords: pinching, Centaurea cyanus, Antirrhinum, Annuals and biennials

I'm starting snapdragons and bachelor's buttons for the first time. The bachelor's buttons are growing a main stalk and then budding. They're 6-12" high. I want more flowers. Can I pinch them back?

Can I pinch snapdragons? Those are only a couple inches high.

Answer:

I checked The Gardener's A-Z Guide to Growing Flowers from Seed to Bloom (Storey Publishing, 2004) by Eileen Powell for the answer to your question. Powell suggests that for snapdragon (Antirrhinum species) you "pinch back young plants after four to six leaves have appeared to encourage a bushy habit. Feed lightly twice before first flowers appear [...]Deadhead often. If blooms become scarce, cut back plants generously, then feed and water generously."

For bachelor's buttons (Centaurea cyanus), the author only suggests deadheading frequently to prolong bloom. A Colorado State University Extension article from 2001 entitled "The Year of Centaurea" describes pinching back:
"Many bachelor's-buttons branch naturally, but you can pinch the growing tips to encourage more branching, bushier growth, and more flowers. C. americana does need to be pinched, or you may end up with single-stalked plants. Pinching perennial cornflower will also give you more flowers, but it isn't required. For slightly larger flowers, you can remove the buds from young plants, but part of the charm of cornflowers is their small, thistle like blooms."

Date 2017-05-26
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Garden Tip

Keywords: Ocimum, Annuals and biennials, Herbs

In France basil is known as herbe royale, while in both India and Italy basil is considered a symbol of love. Read more about this favorite annual herb at www.herbsociety.org/basil/index.php

Date: 2006-02-27
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Garden Tip

Keywords: Alcea, Seed companies and seed sources, Annuals and biennials

Add old fashioned charm to your garden with hollyhocks (Alcea rosea). These stately and edible flowers grow up to seven feet tall in shades of red, pink, yellow and white. Technically biennial (growing leaves the first season, flowering the next summer, setting seed then dying), hollyhocks can be coaxed to flower a few more seasons if stopped from going to seed. The down side to growing hollyhocks is the potential for their leaves to look tattered from rust disease and weevil holes. Never mind - just plant them at the back of the boarder where only their flowers will show.

Here is a source for hollyhock seeds in single colors, plus growing information, pictures, history and lore.

Date: 2007-04-03
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August 01 2017 12:36:01