On 4/29/11 6:35 PM, Higgs Boson wrote:
On Apr 29, 12:35 pm, "David E. Ross" wrote:
On 4/29/11 11:12 AM, Higgs Boson wrote:

Here's a pic of a rosebush that bears abundantly, but most of the
blooms don't open fully. What causes this?
I'm in Zone 8, So. Calif coastal.

TIA

IMG]http://i54.tinypic.com/1zeh00j.jpg[/IM

HB

The roses with brown petals are afflicted with a fungus, most likely
mildew since you are near the coast.

However, many roses never open fully. Only singles and semi-doubles
open fully.

True doubles generally keep opening until they fade. But they have so
many layers of petals that they do not show their centers until the
petals start falling.

That would seem counterproductive in terms of fertilization. If the
insects can't get at the germ material, how can they carry it
elsewhere?

Most true doubles are hybrid teas. The were developed by a person
cutting away all of the petals from a mature flower of one variety and
then collecting the pollen. Then that person cut away all of the petals
and stamens from an immature flower of another variety and then
immediately tying a small paper bag over what is left of the flower.

When that second flower matures, the bag is briefly removed while the
pollen from the first flower is applied. Then the bag is again tied
over the flower. Eventually, a rose hip (sometimes called a pip) forms
with seeds inside.

The stamens are removed from the second flower to prevent
self-fertilization. The bag prevents stray, unknown pollen from
fertilizing the flower.

Notice that NO insects are involved. Also notice that a failure of a
flower to open completely has no impact.

Wild roses tend to have single flowers, which open completely. Heritage
and species roses tend to open completely even if they have double
flowers.

--
David E. Ross
Climate: California Mediterranean
Sunset Zone: 21 -- interior Santa Monica Mountains with some ocean
influence (USDA 10a, very close to Sunset Zone 19)
Gardening diary at http://www.rossde.com/garden/diary