Homegrown: Dividing spring, summer perennials

I have two huge whirling butterfly plants and two lavenders that I need to either move or divide before next year. How and when should this be done?

— Carolyn

Late September through October is probably the best time to divide spring and summer blooming perennials such as the two you have. Just wait until the weather has cooled down a bit.

Doing it while it’s still hot puts additional stress on the plant and occasionally leads to trouble. You could do it early next spring, but doing it now often means you’ll get some flowers next year while dividing in the spring often means a summer without flowers as the plant reestablishes itself.

To divide them, dig the whole clump up and set it aside. Clean off most of the soil around the plant so you can better see it. Cut out and discard any roots or portions of the clump that are dead, soft or rotted. What’s left can then be cut into smaller pieces for replanting.

Most people cut an older perennial into two to six pieces, depending on the plant. You want several sprouts or growth points along with some roots attached in each piece.

Avoid the temptation of cutting your mother plant into too small of pieces. If you do, you run the risk of losing them or creating weak plants that struggle to reestablish themselves.

To cut the clumps apart you can use a large knife you don’t mind getting dull, pruning shears or, use what I often do, a good sharp shovel.

Before replanting, take advantage of having access to the soil the plant is growing in and work in some decomposed organic matter such as Soil Pep or compost.

Our soils need all the help they can get and your plants will appreciate it! The goal here is to give the plant more space and to reinvigorate the plant.

You’re giving it a new lease on life.

My tomatoes are really good tasting, but what causes them to split around the stem?

— Pat

Your tomatoes have growth cracks: circular or radial cracks at the top of the tomato.

It happens when environmental conditions encourage rapid growth of the fruit during ripening. We usually see this when the plant is watered thoroughly after a period of dryness.

Cooler, wet weather will also contribute to the problem.

Growth cracks occur usually when the tomato has reached full size and is starting to turn red. At this point, the skin no longer will expand like it did as the fruit was growing and as it takes in the abundance of water available to it, the skin cracks.

There are a couple of things you can do to avoid the problem. First, try to maintain more even soil moisture; avoid water peaks and valleys.

I know that can be hard when it’s really hot, but try to avoid letting the soil get really dry and then really wet.

Mulching around plant will really help. A 2- or 3-inch layer of wood chips, straw, bark, chopped leaves or other coarse mulching material on top of the soil will help cool the soil, keep moisture in and help even out those water “peaks and valleys.”

Another thing you can do is to allow your tomato plants to sprawl or grow in cages to shade the surrounding soil. Staking your plants up or pinching the suckers off exposes the soil to the hot sun, making the problem worse.

Finally, the fruits are still good to eat unless a secondary rot sets in. Just cut off the cracked area and enjoy.

Dennis Hill is the nursery manager at Bookcliff Gardens, http://www.bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or e-mail .(JavaScript must be enabled to view this email address).


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