Helen Chesnut’s Garden Notes: Pulling horsetail weeds encourages new growth

Dear Helen: I’ve been pulling up horsetail plants on my property and putting them on the compost. When I mentioned this to gardening friends, I was told that, because the plants extract heavy metals from the soil, they are harmful additions to a compost heap. Is this true?

H.M.

It is true that horsetail has been used to help remediate soils polluted by heavy metals. The plants’ extensive and incredibly deep roots are efficient at drawing metals from the soil. The amount of heavy metal in the plants will depend on how much is in the soil. The highest levels are found in areas where the metals have been mined.

I doubt that the soil in most home gardens will be heavily laden with dangerous metals, but if this is a concern the history of the land could be looked into. In benign soils, the plants extract and hold minerals that are useful additions to a compost.

Personally, because this is such an aggressive weed, I would treat the stems before composting them. Either soak them in bins of water for a week or lay them out in the sun on plastic sheeting to dry thoroughly.

Your email indicates that you don’t mind the horsetail on your property. Most gardeners regard the plants as pernicious weeds, almost impossible to control. Should you wish at some point to begin curtailing their spread, refrain from pulling the plants up or digging them. These actions prompt underground nodes of growth to sprout new plants.

A preferred control is to keep cutting the stems to the ground, beginning with the leafless, spore-bearing spring stems. Cut them before they can form and spread spores, which can germinate in moist soils. Then cut down the leafy stems that follow. Continued cutting will gradually weaken the roots.

If it suits the situation, an early summer cutting could be followed by covering the area with thick black plastic for a year. If you don’t like using plastic, another option is to cover a horsetail-denuded area with cardboard thick enough to hold together well for at least a year. Top it up with layers of newspaper if you wish. Then cover with a thick mulching material.

Dear Helen: In the last few years an Italian prune plum tree in my yard has produced only around 20 plums each year. The tree is an old one, dating back to the 1960s I think. I would be sad to lose the tree, but I fear it is in decline. What can I do?

P.C.

Fruit trees, like most living things, have a finite life span. For prune plum trees, the average is 15 to 20 years, with 30 years being exceptional. Our damp coastal climate renders plum and other soft tree fruits susceptible to a number of diseases that can weaken a tree and further limit its productive lifetime.

My 40-year old prune plum tree still yields good crops of delicious plums, but parts of the tree are beginning to die back and I can see the beginning of its decline. Your tree is considerably older and is giving you few plums. If I were you, I’d begin planning restoration measures on a tree you clearly would like to survive and, at the same time, begin searching for a suitable site for a new tree to plant in the spring.

A new tree will take a few years to begin fruiting. Meanwhile some pruning may help to restore the old tree, even if for a short while. For disease prevention in plum trees, summer pruning is best. Aim for a flat-topped, spreading shape with the centre area thinned enough to allow for optimum air circulation and sunlight exposure. I’m considering spring and summer seaweed fertilizer sprays for my tree. Gardeners I know claim the sprays help to keep fruit trees healthy.

I can’t imagine being without my own prune plums. They provide favourite treats: plum cakes, pies, and clafoutis, sauces and jams.

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Plant sale

The Horticulture Centre of the Pacific, 505 Quayle Rd. in Saanich, is opening its fall plant sale to in-person shopping starting tomorrow (Thursday, Sept. 24) during regular garden hours (Thursday through Sunday, 10 a.m. to 4 p.m.). Shoppers are asked to bring a mask and wear it when physical distancing is not possible. View a plant availability list at hcp.ca.

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