Willow Glen Resident

Gardening

Biennial Bloomer: Hollyhocks are biennials often grown as annuals. They self-sow easily, tolerate less-than-perfect growing conditions and bloom in a variety of colors.

Don't be impatient, there's still time to plant impatiens

By Tony Tomeo

Petunia, marigold, lobelia, alyssum, impatiens and snapdragon are among the most popular annuals that are at their best this time of year. Less common but also popular are cosmos, celosia, nicotiana (flowering tobacco), verbena and zinnia. If they did not get planted earlier as weather began to get warmer, any of these warm-season annuals can still be planted from cell-packs and will grow quickly, making up for lost time. Nasturtium seed can be sown anytime. It is only beginning to get late for hollyhock and some of the larger sunflowers, which need some time to grow before blooming later in the season. Like nasturtium, sunflowers are most easily grown from seed.

Hollyhock and sunflower get rather tall, so are good choices for sunny areas against fences or behind other low-growing annuals. The largest of the single-flowered sunflowers are so tall their flowers are above the eaves and cannot be seen from inside the home if they are just outside. Their foliage is nice though, and can temporarily shade south- and west-facing windows through the hottest part of summer. They need only to be planted in a row where the eaves end.

Until the weather is dry enough (minimal humidity) to inhibit fungal diseases, powdery mildew can be a problem for any of the warm-season annuals, and very often infests snapdragons and zinnia. Snapdragons and hollyhock are also very susceptible to rust. Many people have already noticed that some susceptible woody ornamentals, particularly roses, have been seriously afflicted with powdery mildew. This may be a difficult season for annuals as well.

It is easiest to avoid powdery mildew and other plant diseases by growing plants that are less susceptible. Of course, innate disease susceptibility of the various plants is affected by the environmental conditions of each particular garden. For example, some people have no problem growing snapdragons but find their verbena gets powdery mildew. In other gardens, verbena is very healthy, while snapdragon succumbs to rust. I actually gave up on snapdragons years ago but have plenty of other options.

Fungal diseases thrive in humidity, so are not very happy when the air gets dry. Although weather conditions cannot be modified to suit gardening needs, certain gardening techniques can be modified to decrease humidity in the garden. Ambient moisture will dry more efficiently during the warm and sunny part of the day if the garden is watered in the morning. If watered too late, moisture will linger through the night. Pruning overgrown plants to improve air circulation will also help to decrease humidity. Removal of badly infested plant parts does not change humidity, but decreases the abundance of spores that continue infestation.

With the exceptions of lobelia, alyssum, impatiens, verbena and perhaps only a few others, annual flowers perform better if dead-headed. This procedure, which is simply the removal of fading blooms, prevents seed production. Resources that would be needed for seed production can instead be diverted to continuing bloom.

Flower of the Week: Hollyhock

Hollyhock, Alcea rosea (or Althaea rosea) is grown as a warm-season annual, but is actually a biennial that is happy to bloom the first summer. (Most biennials produce only foliage in their first year, and bloom and later die in their second year.) Those that bloom earliest can actually bloom again in autumn if their first flower spikes get cut down to just above the basal foliage as flowers fade. New plants can still be added to the garden, but it is too late to sow seed for this year. Seed can be sown at the end of summer for bloom next year. Earlier blooming varieties can be sown in early spring for summer bloom.

Hollyhock is one of the boldest annuals. The shortest varieties produce single flower stalks that are more than 2 feet tall. Old varieties can get 9 feet tall with basal foliage as wide as 3 feet. The coarse, lobed leaves are sparse on the flower stalks, and fuller and larger at the bases. The approximately 4-inch wide flowers can be single, semi-double or double, in shades of white, pink, red, purple, pale yellow and peach, as well as a very dark red that looks black.

Horticulturist Tony Tomeo can be contacted at 408.358.2574 or at LGHORTICULTURE@aol.com.