Plant Doctor Archive

Red-less rhubarb

OVER a period of five years I have bought five different rhubarb plants from various respectable garden centres - one each year from a different centre and each of them with beautiful healthy red stems. Can you please tell me why the red stems disappear and are replaced by green ones soon after planting? I put compost in the bottom of each hole along with sheep pellets at the time of planting and each plant gets given periodically a drink of liquid chicken manure.

RHUBARB is naturally a cool-climate plant that grows and crops better in areas that get cold winters - it can tolerate temperatures as low as -15°C. It also needs plenty of water and nutrients during spring and early summer when going through its maximum growth phase. Rhubarb stems generally tend to be redder early in the season and in lower light conditions, so for your area I recommend you plant it in a cool, shady spot and make sure the soil stays moist. You're doing the right thing with sheep pellets and liquid manure, but you may not be applying enough nitrogen, so also use lots of general compost, both added to the soil and as mulch around the crown of the plant. Feed during the growing season with high nitrogen fertiliser such as Thrive or Nitrosol to encourage lush growth.

The other point to bear in mind is young rhubarb plants can take two to three years to reach their potential, so don't pick off too many leaves until the clump is well established and even then, from around mid-summer, allow plenty of leaves to stay on the plant to keep the crown strong and healthy for next season. Also, cut out any flowers when they appear as they'll suppress leaf production.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.