Protea longifolia is easy to grow and responds well when propagated by seed, however, cuttings is also used but takes a while to root. Sow the seed in autumn, March to May, in a well-drained sowing medium of coarse sand and fine-milled pine bark. The dropping of the temperature in autumn breaks dormancy and stimulates the germination of fynbos seed. The optimum temperature for germination is 5–10ºC for night temperature and 15–20ºC for day temperature. It is important to select the fertile seeds before sowing; fertile seeds are plump, whereas unfertile seeds are not. Protea seeds are very sensitive to waterlogging. Use a well-aerated pot with good drainage. Smoke treating the seed with dry and green fynbos material stimulates germination. At Kirstenbosch, seed trays are placed in a plastic tent into which smoke from burned fynbos is piped. Smoke extract is also available for sale from the seedroom. Treat your seed with a dusting systemic fungicide which contains the active ingredient metalaxyl, to prevent the post emergence seedling infection.

After sowing cover the seed with a light layer of sand to cover any exposed seeds. Keep the soil moist and apply fungicide once a week. To prevent birds and rodents from eating the seeds, cover the benches or trays with a grid. Once the seeds have germinated, they will produce the cotyledons, followed by true leaves. The seedlings are ready to be transplanted into small plastic bags or into compartmentalized trays when they have true leaves. Place the potted up seedlings under shade net for hardening off if conditions are dry and hot. At Kirstenbosch the seedlings are placed in a shade net in the nursery until they are ready to be planted into the garden after a period of 1 to 2 years. Shade net reduces the direct sun which can dry out the soil in the plastic bags and can also prevent the scorch.

Protea longifolia is a water-wise shrub once it is established in the garden, normally 3 years after it has been planted in the garden. Plant the seedlings in acidic soil preferable between 5–7 pH levels. Protea longifolia grows naturally in nutrient-poor soils, more specifically where phosphorus is scarce. Use lower concentratons of organic fertilizer to encourage the sensitive proteoid root and avoid using artificial fertilizers containing phosphorus, as they can cause the plants to collapse and eventually die.

Protea longifolia can also be propagated by cuttings. The cuttings can be taken in summer, from November to April, from the semi-hard growth of the current season. Select disease-free cuttings of 200 to 250 mm long from upright-growing lateral shoots. Dip the cutting in rooting hormone for at least 5 seconds. Place your cuttings in a well-drained and aerated rooting medium of 70% perlite and 30% fine-milled bark, or coarse sand and finely milled pine bark, in multi-trays. Put the trays on bottom heated benches of 22–25ºC and regularly treat the cuttings with the fungicide to prevent fungal infections. Remove the dead leaves and wilting cuttings until your cuttings are rooted. Rooting the cutting of Protea longifolia is quite difficult and the cutting can take 3 months to root. Monitor the cuttings and if not rooted, damage the callus, retreat with rooting hormone and replant in fresh rooting medium.

Keep the soil moist during the hot dry summer season by mulching your bed with an about 5 mm thick layer of compost. The mulch will keep the roots cool, keep moisture in the soil and reduce the growth of weeds. Protea longifolia needs to be pruned after flowering to encourage the new growth and to compact bush.

Nocturnal beetle such as Snout Beetle can cause leaf damage by feeding on the leaves during the night. Control the beetle by using a bright torch in the night and place a wide, open container under the tree and shake them off and crush their hard exteriors. Protea longifolia is also susceptible to Phytophthora cinnamomi. Graft Protea longifolia scion on hybrid ‘Pink Ice’, a cross between Protea compacta and P. susannnae. There are various hybrids that are resistant to phytophthora and other various pathogens which can be used. At Kirstenbosch in the motherstock area, P. longifolia plants are doing very well without hand watering. Phytophthora spores become more active when the soil is warm and wet in summer season. Planting in winter season in Mediterranean area encourage the roots of plant to spread and goes deep into the soil to avoid the need for watering in summer time.

Protea longifolia has been reported to be affected by Armillaria. To control the pathogen, apply the prevention method of avoiding to use the infected mulch, bark chipping, compost, chipping wood and bark and remove the infected plant and burn it immediately.