Growing Concerns 519: Fertilizer perscription, dogwood, vinca flowers

Late Spring!

Cut your losses on winterkilled trees then pamper and shape what's left


Dear Janet,

What should we do with dogwood trees that didn't bloom this spring?

I bought mine only 4-5 years ago so it's not very big. I did notice last week that some older, established dogwoods were blossoming but not profusely.

I now have some leaves appearing, but only on one side of the tree. There are three major limbs. One is definitely dead because I've cut several twigs and there isn't a speck of green inside. Should I prune the entire limb or wait and see what happens next spring?

Does it do any good to feed the tree Miracid now?


Dear A.W.,

Add flowering dogwood (Cornus florida) to the lengthening list of this winter's casualties. I had hoped that these trees lost only their flower buds but count them now with pines, hollies, azaleas, rhododendrons, false cypresses, redbuds, poplars, sassafrases, hawthorns and others killed in whole or part this winter.

Which combination of factors killed this tree and not that one, or some branches but not all of a given tree? Let's leave that detective work to others, so we can focus on determining what's worth saving and begin rehabilitation.

You're right to look for moist green cambium tissue under the bark. If a twig lost the leaf buds it set last year but still has live cambium, it may yet develop new buds.

This will require energy, which must come from sugars produced by surviving foliage or starchy reserves in limbs and roots, sent to defoliated limbs through the cambium. So plants with more leaves, bigger roots and thicker twigs are more likely to revive than those with scant green or roots weakened by transplant or drought.

Replacement leaves develop over weeks, not years. If bare limbs don't show new growth within a month after nearby plants of the same type have leafed out or intact buds on other limbs have opened, start pruning.

Fertilizer is important once growth begins. It does not initiate growth, nor can it supply energy to plants. It's not food but vitamins, given to actively growing plants just as we supply vitamins to children.

To "feed" recovering plants, water well and let as much light as possible reach them. They'll use light, water and gases from the air to make the sugars and starches that are true plant food.

Losing a main limb is tough but if it's dead, remove it. Cut to just above a husky new bud or surviving branch. Then train new growth into position over the next few years. Don't despair -- replacement limbs develop quickly on trees that are healthy in their other parts.

Training new growth means disbudding to thin crowded shoots as they appear, selective pinching to shorten new growth while it's still soft, or gently bending and using non-binding restraints on pliable shoots to coax them into the desired positions.


Dear Janet,

I planted some vinca flowers in pots on my deck and they seem to be dying. I planted impatiens at the same time and they are doing well. Is vinca more susceptible to cold? Is there a way to bring them back to life?


Dear B.C.,

You can be a plant doctor if you start with a thorough exam. Dig out one of your ailing patients to look closely at its leaves, roots and stem.

If the roots are white or light colored, thick and firm all  the way to the tips, and the stem is sturdy and uniformly colored right to its base, the soil temperature and water have probably been okay. In that case, poor growth or dieback might have come from frost, drought or overfertilization that affected only the youngest leaves and outer branches. Since the plant has a healthy stem and viable roots, you can prune off dead leaves and branches and expect new growth. Whether this is best depends on how much of the plant you'll lose in the trimming and how quickly you need a full look.

If the root tips are mushy and dark or the stem has sunken soft spots or wet wounds, then cold soil and moisture probably killed cells which were then attacked by stem rot or root rot fungi. We shouldn't expect a young annual to overcome rot. It might survive but remain sickly all summer. Better to replace them, along with the soil immediately around those roots.


Short report

Stumped by fertilizer figures?

Enlist your household's math whiz or number puzzle hound. Hand that person the fertilizer prescription from your soil test result, a list of the three-number labels from fertilizers already in your possession, and today's thumbs up and thumbs down. Let the high math commence while you go back out to weed!


Green thumbs up

to those who will calculate on behalf of gardeners. Don't tell us how, just tell us that each pound of the 10-6-4 fertilizer listed on a soil test might as well be two pounds of 2-2-2 Driconure plus half a pound of 12-0-0 blood meal and one-tenth pound of 0-10-0 bone meal!


Green thumbs down

to manufacturers who prey on fertilizaphobia with such tactics as packaging the same 5-10-5 as "vegetable food" and separately as "rose food." They know we'll buy both, just as we'll buy a 12-12-12 rather than using the 20-20-20 we already own at three-fifths strength.

Originally published 6/7/0