Tuesday, February 26, 2008

Cold frame treasures

In addition to bulbs, the cold frame houses a variety of other plants. Most of these are not suited to life in the open garden, and each represents a significant extension of my horticultural horizons in a new direction.

For example, there is a young seedling of Sophora secundiflora. In a very sheltered place, this might be hardy in the open. Mature plants have fragrant flowers which suggest wisteria. It’s a very handsome plant and all but unknown in gardens in this area.

A seemingly thriving plant of Cistus psilosepalus has me hoping that I might soon see a rock rose actually blooming in this garden. I’ve tried others in the open air, and they quickly went from bad to worse. Various cistus have been described as hardy in this area, but it’s not simply a question of hardiness in the sense of cold tolerance. The climate here is all wrong for them. The little seedling I planted into the ground in the cold frame has slowly grown all winter: it looks like it’s ready to take off once the weather moderates. The cistus I really want are the ones with fragrant foliage; if the current experiment proves to be successful, I’ll try one of those.

Several of the asarums are temporarily in the protected cold frame. These are Asarum nobilissimum and A. maximum. Last summer they grew in a spot which got plenty of sunlight and it seemed to do them good. I doubt if their foliage will have a chance in the open air, so they went into the cold frame for the winter.

There are also several rosemary plants; these were rooted from grocery store material sold for culinary purposes. Rosemary is like cistus: it’s not really hardy here in my experience, although an occasional plant might survive for years. Again, it’s not simply a matter of cold: the climate in general here is wrong for it.

Another occupant of the protected cold frame is little Smilax pumila. An earlier trial of this species in the open air was somewhat successful. The plants grew and went on to bloom – but the developing seed was killed by winter cold. I’m hoping that they will be right at home in the protected frame.

Ceratostigma griffithii occupies a corner of the cold frame. I doubt if this plant needs cold frame protection, but at the time the frame was built the Ceratostigma was still in a pot and needed a home. Because it blooms so late in the year, the frame seemed to be a good choice. It has made itself right at home.

Ruscus hypoglossum is also spending the winter in the frame. I expect this to be hardy in the garden, but I have not yet decided where to put it.

There is also a little plant of Calluna vulgaris ‘Mrs. Ronald Gray’: this is there to remind me of my plan to grow a variety of little evergreen shrubs in a cold frame. Heaths, heathers and broadleaf evergreens have never become common in our gardens; I think the main reason for this is that they experience so much foliar damage that they emerge from the winter ugly. Cold frame protection should prevent that.

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