Rules of return for spring bulbs and pruning crepe myrtles

To keep bulbs coming back year after year, don\'t plant annual flowers over or near them -- dig them up when the leaves turn brown and replant them in fall. (Getty Images)

Meet Mike this weekend

Saturday, April 26: Prince William County Compost Awareness Day; Balls Ford Road Compost Facility; Manassas, Va. 20112. Free! Mike will give a talk on how to make, buy and use compost correctly at 10:30, with a brief (half-hour) compost Q & A at noon. More info here.

Saturday and Sunday, April 26 and 27: TomatoMania! Mike will tell you how to grow your best tomatoes ever in a pair of free talks at Greenstreet Gardens:

Saturday, April 26, at 2 p.m. at Greenstreet’s Alexandria location, 1721 West Braddock Road; Alexandria;

Sunday, April 27, at 1 p.m. at Greenstreet’s Maryland location, 391 West Bay Front Rd., Lothian, Md.

More info at 410.867.9500 or here.

Flowers on Top Make Spring Bulbs One-Time Wonders

Sid in Laurel writes: “I planted a lot of tulip and daffodil bulbs at my parents’ house last fall, which they are enjoying thoroughly this spring. My mom would like to plant annuals in the same flower bed, but I’ve heard you warn against this and know that I should dig out the bulbs and re-plant them in the fall — but I doubt I’ll have the time to do this every year. Can I plant annuals near the dormant bulbs and expect the bulbs to be healthy next spring?”

Sadly, the answer is no, Sid. In their native habitat — the most God-forsaken mountainous regions of Turkey, Afghanistan and Russia — winters are cold and snowy, spring is brief but delightful and then summers are scorching hot and dry. Those are the conditions that favor the return of the flowers year after year.

Our habit of planting — and then watering and feeding — annual flowers over top leads to the exact opposite of those conditions, and tends to rot the dormant bulbs below. That’s why I dig most of mine up after their leaves go brown, store them in the basement and then replant them in the fall. It’s not as much work as it sounds, and I have an amazing rate of return — even with famously feisty rare tulip varieties.

The smart money says to dig them up and store them this season, and then plant them in the fall in a more out-of-the-way spot that doesn’t cry out for a summertime replacement show.

Spring Bulb Rules of Return

Want your spring bulbs to return and bloom again for you next season?

Quickly clip off the flowers after they fade to prevent wasted energy going to the seed heads. (Just the very top of the flower stalk — not all the way down.)

Do not cut off any of the leaves. Those leaves must be left unmolested to collect the solar energy to fuel the following year’s flowers.

And don’t tie them up either. “Bulbs in Bondage” also prevent that energy collection (and may reveal more about you to your neighbors than you’d like).

Do give them a nice feeding of compost, worm castings or other gentle organic fertilizer; right after flowering is when spring bulbs should be fed.

And don’t plant annual flowers right over top of them. For the best rate of return, dormant bulbs should not be fed or artificially watered over the summer.

Begetting Better Bloom on Lilacs

Arnie in Burke writes: “My lilac bush is in full bloom, but with one less purple flower than last spring — that’s down from three to two. Why am I not getting more blooms on a very mature bush that appears to be quite healthy with plenty of green leaves?”

The biggest cause for disappointing bloom on these drama queens is lack of sun, Arnie. Lilacs require full sun to bloom their best. After that, they need to be far away from lawns that are fed nitrogen, and they should never be fed directly with manure or other high-nitrogen fertilizer. Nitrogen reduces a plants ability to flower.

But you can give them a cup of rock phosphate — a natural mined mineral — covered with an inch of compost this spring to induce better blooms next year. Phosphorus is “the blooming nutrient,” and rock phosphate is the best source. But just use one cup per plant and only apply it once every three years. A little goes a long way and lasts a long time.

Prune, But Do Not Murder Your Myrtles

Margot in D.C. writes: “Is it OK to prune my crepe myrtle now?”

Yes, Margot — in fact this is the perfect time of year to prune crepe myrtle and other plants that bloom in mid-to-late summer. And pruning now will increase the amount and quality of the flowers that will follow. Crepe myrtles really respond well to a spring haircut.

But don’t commit “crepe murder” by hacking the poor plant all the way back to the ground or you’ll wind up with a very lopsided, bottom-heavy plant after a few years. The ideal for crepe myrtle is to remove about as much height as the plant grew last season, typically one to two feet. This should keep the blooms down at a comfortable eye level while respecting the structural integrity of the plant.

Seed Starting: Turn the Heat Off, But Keep the Lights Tight!

Kirsten in Stafford has a very important question. She writes: “How long should we leave the heat mats on under our seed-starting flats after the seeds have sprouted? We started the seeds under four-foot-long fluorescent tubes, raising the lights as the seedlings grow, keeping the lights as low and close to the plants as possible as long as they are indoors. Hope this is all correct!”

Half and half, Kirsten.

Bottom heat is only used to germinate the seeds. Heat mats should be turned off as soon as the sprouts are up. Leaving them on can cause mold problems on the soil and keep the young plants too warm, causing severe transplant shock when they go outdoors into soil that’s still relatively cool at the ideal planting time of mid-May.

But keeping the young plants as close as possible to those fluorescent tubes is the absolute right thing to do. And 4-foot-long tubes are the best! People who skimp on the light when they try starting their own seeds always end up with tall spindly (“leggy”) unhealthy plants. Keeping them close to the (cool) fluorescent tubes produces shorter, stockier plants that get off to a great start outdoors.

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