Weather: The winter of 2003/04 was generally mild. December and January were mild and wet, with the occassional sharp frost, but no prolonged period of cold weather. These conditions continued until the middle of February, when a period of clear skies and high pressure with northerly winds set in for the remainder of the month. During this period several degrees of overnight frost occurred repeatedly, but temperatures rose above freezing during the daytime. Towards the end of the period the ground remained frozen during daytime. This was followed in early March by similar conditions, but with a greater degree of cloud cover and overnight frosts only on some nights.
Observations
Annuals and Biennials: As might be expected those annual and biennial plants which flowered the previous summer did not survive the winter. The first to go, in early winter, were Lavatera trimestris and Malope trifida. Hibiscus trionum died early in the New Year. Lavatera mauritanica, Malva linnaei (Lavatera cretica) and annual ('Braveheart') and biennial ('Mystic Merlin') strains of Malva sylvestris held out until the cold spell in late February.
Seedlings of Lavatera mauritanica and Malva sylvestris that has not flowered in the previous summer did survive. This was not the case for similar seedlings of Malva linnaei.
Herbaceous Perennials: Specimens of Malva moschata and Sidalcea ×hybrida all came through the winter without ill-effect. This was also the case of most specimens of Lavatera thuringiaca and Malva alcea, but one specimen of Lavatera thuringiaca lost some shoots, and a specimen of Malva alcea was lost. In the former case I suspect that the cause was cold wet conditions, rather than frost.
Perennial forms of Malva sylvestris ('Marina' and a sterile blue-flowered plant of 'Mystic Merlin') survived, as did specimens of Alcea rosea.
The resting buds of Althaea officinalis 'Alba' were scorched by frost, but the plants produced additional shoots from the rootstock.
Subshrubs: A specimen of Anisodontea capensis was uneffected by the winter conditions until the cold spell of late February, during which it lost about half its top growth. This same cold spell finished off the top growth of Lavatera ×clementii 'Candy Floss', necessitating treating this as a herbaceous perennial (the basal shoots produced in the autumn were unaffected). Some top growth of Lavatera ×clementii 'Lisanne' and Lavatera ×clementii 'Burgundy Wine' was also killed.
Specimens of Sphaeralcea ×hybrida 'Los Brisas' appeared to had been hard hit by the cold spell, but recovered.
Shrubs: Assorted cultivars of Hibiscus syriacus came through the winter without ill-effect.
Fremontodendron 'California Glory' was unaffected by the winter conditions.
A specimen of Lavatera 'Bicolor' lost some branches during the cold spell of late February.
Cultivars of Lavatera ×clementii and Lavatera olbia generally came through the winter unscathed, with the exception of the less shrubby forms mentioned above. In a mixed planting of 'Bredon Springs' and 'Rosea' observed on a exposed ridge at 1000 feet asl, plants of 'Bredon Springs' apparently came through unscathed, while those of 'Rosea' were extensively cut back by the frosts.
Specimens of Abutilon ×hybridum (6 specimens of 5 clones) all lost their foliage progressively over the winter, but all survived without major damage.
© 2004 Stewart R. Hinsley