Growing Concerns 518: Catalpa tree, thistle, ash

Late Spring!

When planting a catalpa tree, why not aim for a new national champion?


Dear Janet,

Where can I purchase catalpa seeds or trees?


Dear S.M.,

The northern hardy catalpa (Catalpa speciosa) is often called cigar tree or bean tree for its long seed pods. Detractors call the tree messy for these big pods and its relatively brittle wood that can lead to some twig fall. Yet the tree's big white flowers in summer and craggy winter form are assets in the landscape.

You can buy a catalpa locally if you look around a bit. Use the internet to find places close to you.  There are also places that will ship the tree to you.  Just be sure to use the botanicle name.  Common names can be different depending on your location.

For seed, just wait until late fall and collect some pods. The seed sprouts readily with no treatment other than popping it from the pod before planting.


Dear Janet,

I'm ready to give up and turn my flower bed over to the thistle weeds growing in it! I dug them out and pulled the sprouts all last year but they're back, as nasty as ever! Is there any hope?


Dear C.B.,

Weeds have the upper hand in many situations because they're persistent. So it's only fitting that persistence on the part of the gardener is one of the keys to beating them.

Here's my standard approach to perennial weeds. It sounds like you may already have completed the first steps, last year -- so despite appearances, you're in the home stretch!

If it's a perennial bed, lift the perennials out of the bed. Take large root balls, mist them, then set them aside in the shade and they'll be fine for a few hours or even a weekend.

Dig up one thistle and learn what its root looks like -- brittle and white, in the case of Canada thistle, with thick horizontal segments. Now dig through the bed methodically, removing every bit of root you find. Note any place where the thistle root has entered the bed from adjacent ground, and how deep the roots are running at that point.

Now rinse all the soil off the root balls of the on-hold perennials. Remove every bit of foreign root. Replant them. If the weed was entering the bed from surrounding soil, dig a trench around the bed or install a vertical root barrier -- making either the moat or edging material as deep as the weed's runner roots.

Patrol the bed regularly -- daily is wonderful but weekly can work -- to remove every weed shoot you see. Be sure to "lift the skirts" of your desirable perennials to roust out the weed shoots that may be nestled there. Producing such growth uses up starch from the root fragment at the weed's base. Each day the shoot is in the sun, however, it creates new starch to rebuild the root. So the more frequently you nip these survivors in the bud, the sooner you starve out the remnant roots.

Don't be discouraged in year two. The world wouldn't be green if Nature gave up so quickly. Despite first appearances, the weed is weaker this year than last, so keep breaking it off and rooting it out.


Short reports

If you cut down an ash tree but can't chip it...

...and suspect the tree was infested with the borers  cover the wood securely with a plastic tarp until next winter. That's because borer beetles will emerge even from cut wood. Removing the bark is not an adequate defense as the larvae of this beetle tunnel into the wood to pupate.


Green thumbs up 

to pansies, which seem to have encountered ideal seed germination conditions this year and are coming up like a green carpet wherever pansies grew last year. As with other self-sown species such as sweet alyssum, cosmos, cleome and pot marigold, all the gardener need do is to thin the plants to leave one every three or four inches and enjoy your free flowers!


Green thumbs down

to carpet roses as groundcover, firethorn as a wall covering and barberry as a formal hedge. Why choose such viciously thorny plants for situations that require regular close hand work? Groundcover roses must be weeded regularly until established. Firethorn and barberry need frequent shearing for a formal appearance. Oh, my poor pricked fingers!

Originally published 5/31/03