Grevillea gracilis Alba

Culture:

Grevillea gracilis Alba is best planted in spring, after the last frosts. It prefers soil with an acidic to neutral pH, sandy, loamy, or poor and very well-drained. The presence of limestone in the soil causes yellowing of the foliage, chlorosis, which weakens the bush until it eventually dies. This condition can be corrected by regular application of iron in its chelated form (sequestrene). In regions where the soil and subsoil are limestone, dig a large hole 60 cm (23.6 in) in all directions, filled with ericaceous soil or compost and non-limestone sand. Growing in pots allows better control of the substrate and allows the plant to be stored frost-free in areas with limited hardiness (up to -7°C (19.4 °F) at the peak for a well-established plant).

Grevilleas are drought-resistant plants once well established: monitor watering during the first 2 summers, after which it will become optional or even unnecessary. In the ground, they appreciate a thick layer of mulch. Use wood chips or grass clippings. It is recommended to use a fertilizer very low in phosphorus, as it can decrease the plant's drought resistance by destroying the dense root hairs that develop just below the soil surface. A N-P-K fertilizer with proportions of 18-2-10 is well-suited.

In pots, prefer Grevillea species and varieties with low growth. Use a lightweight, well-drained potting mix that remains moist. We recommend the following mixture: 60% pine bark, 20% coarse river sand, 10% fine river sand, and 10% clay soil for water retention. The pH should be 7 or less.

Insects and diseases:

Grevilleas can develop black leaf spots, caused by a rarely fatal fungus: a fungicidal treatment will eliminate it.

Rotting of the collar can also be a problem, a deadly disease also caused by fungi that develop in moist and warm soil. Avoid burying the plant's collar, which should be exposed to air. Avoid watering too often in hot and dry weather; let the soil dry out between waterings.

Phytophthora (cinnamomi), a disease also caused by a fungus, affects many plants in dry areas. The parasite destroys the roots during excessively rainy winters. The plant may suddenly wither in summer due to lack of water as a result of the destruction of part or all of its roots. Partial or complete death of the vegetation or branches can be observed in severe cases. Prevention is crucial, as the disease is almost impossible to eradicate: ensure that the soil drainage is perfect, remove the excess water from the saucer placed under the pot, and remove dead or diseased parts.

Pruning:

Grevilleas tolerate annual pruning well, during their growth period or just after flowering. Shorten the branches by one-third of their length. Regularly pruned bushes will be more branched and more floriferous.