Dear Helen: Last fall, my neighbour allowed me to dig some rhubarb plants from her garden. They are not doing well in my garden. Half of the root sections I transplanted have some yellowed leaves and withered stalks. I鈥檓 wondering whether I听didn鈥檛 prepare the soil properly or I听planted at the wrong soil depth.
A.P.
Because rhubarb is a perennial crop that usually occupies a site for five years or more before being lifted, divided and replanted, a thorough preparation of the soil is especially important. That means a deep digging of the planting site, removing weeds and debris, and incorporating composted manure or/and compost deeply into the soil.
You mention planting 鈥渞oot pieces.鈥� Ideally, these should be cut cleanly, with a sharp knife, from around the outside of a lifted plant, where the youngest portions of the plant crowns will be located. The crown is the surface from which top growth proceeds.
There should be at least one growth bud on each piece to be planted, and the crown should end up just beneath the soil surface. October and March are ideal times for dividing and planting rhubarb.
Keep rhubarb plants well watered during dry summer weather. Consider mulching the plants with compost now, after a deep watering, to help build the roots up. A certain amount of leaf yellowing and stalk withering is normal in rhubarb, but if the ailing plants continue to fade away consider lifting and discarding them. Prepare new sites听and plant purchased roots in the fall or spring.
听
Dear Helen: I found an unusual plant at one of my local garden centres. It鈥檚 an evergreen shrub called mint bush (Prostanthera cuneata). Can you give me some ideas on its care?
D.T.
The common name for Prostanthera cuneata is 鈥渁lpine mint bush.鈥� This is not a plant I鈥檝e grown, but it is described as a dense and compact, evergreen Australian shrub with small, soft leaves. The white to mauve flowers in late spring and early summer are trumpet-like, with two lips. The plant will grow to one metre in height, with a spread of up to 150 cm.
The leaves on all Prostanthera species are dotted with glands that release a minty smell when crushed. The plant鈥檚 preferences are for a sunny, sheltered site with a soil that drains efficiently of excess moisture. Make sure the soil is kept moist in dry weather. Prune lightly, immediately after flowering. The plants do not respond well to hard pruning. Alpine mint bush is recommended for growing in containers and rock gardens.
听
Dear Helen: I have many large heathers in my garden. Some are one听metre tall and wide. Occasionally they need to be cut back severely, but听when I听cut them back into old wood, that is beyond green growth, that part of the plant dies. Sometimes the entire plant expires. How can I avoid harming the plants when I prune, and is there a听preferred time of year or method for听reducing the size of heathers?
H.A.
Heathers are kept as compact and neat as possible by cutting them back after flowering. It is most common to remove just the faded blooms, but as much as half the length of flowered stems can be removed.
Yearly post-bloom pruning is the best way to keep heathers compact and听youthful, but eventually most become woody and straggly beyond redemption. Then, it is best to dig them听out, renovate the soil, and replace them with young transplants. The ones that settle in most easily and flourish best in my garden are very young heathers, purchased in 10-centimetre wide pots.
GARDEN EVENT
Water garden tour. For the Love of Africa Society will host its 10th annual Water Garden Tour on Saturday, 9:30 a.m. to 4:30 p.m. This self-guided tour of 10 Greater Victoria water gardens will include musicians playing, artists, master gardeners, and designers to answer questions on ponds, fountains and more. Tickets听at $25 are available at various vendors and online. Find this information at watergardentour.ca or call 250-891-0762. Proceeds from the tour go to support the society鈥檚 current project, a trade school in Tanzania. fortheloveofafrica.ca.
