|Mike's Gardening Tips
Be Careful How You Fill That Hole in the Ground!
Q. Hi Mike! Last spring a big crabapple blew over and the stump had to be ground out. Now I have to fill in the hole (an area of about 20 sq. feet) before planting either a Franklinia or a Yellow Magnolia I bought last
spring at a U of D native plant sale. So far I've been filling in the area with composted leaves that the city provides. My question is do I need to get other dirt too? My native soil is such nasty clay that our plantings have had to be preceded by digging in tons of peat just to make it plantable. Any suggestions?
A. Yeah-rent a time machine, go back to last Spring, leave the stump IN the ground (cut flush with the soil), and build a beautiful raised bed that you will fill with flowers and shrubs over it so you won't have a big hole in the ground to worry about!
No? Then let's stop you from making some other mistakes. It is NOT a good idea to plant any tree in an 'island' of rich soil. The tree's roots will stay tucked nice and warm in that little soil womb instead of spreading out into your Crappy Clay like you need them to do for good growth-and for not falling down like the previous tree did. When planting most trees, you should fill the hole back up only with the same lousy dirt you removed so that the roots HAVE to reach out looking for something better. Any compost or other soil improvements should be added afterwards (on top).
Your two choices, however, are far from normal trees-especially for our area. Although the Franklinia IS named for our famous 'Dirty Ben', it hails from Georgia and prefers a warmer clime than ours. It WILL survive, especially in a sheltered area, but will never look as nice as it would if grown down South.
Magnolia?! Which one??? Some are hardy all the way down to zone 5 (North of us); some would perish in their first winter here. Some are deciduous (lose their leaves in winter); some are evergreen. Some magnolias (including yellow-flowered ones like the 'tulip tree') bloom too early for our climate, and frost kills their flowers most years. No matter WHAT kind you have (something you should definitely find out if you don't know for sure), it needs to be planted in a sheltered spot. (Actually, it would prefer to be planted in Georgia, but.)
Anyway, both those trees require a soil much richer than most, so instead of all Crappy Clay, I'd fill the hole with a mix of two-thirds soil (cheap 'top soil' or yes, your Crappy Clay) and one-third compost. "Composted leaves", huh? If it looks like rich soil, use it. If it still looks like leaves, DON 'T use it-and clear out the hole and start over; your new tree needs to be well anchored and loose leaves won't do it.
And stop with the peat moss! It conveys no nutrition whatsoever, and it makes the soil severely acidic, which is good for some plants, like azaleas and rhododendrons, but not most trees. (To further confuse the issue, some magnolias like an acid soil, while some like it alkaline; furthering your need to know exactly what you have.)
I strongly suggest you plant something more truly native and/or reliably hardy in our area instead. The crabapple that blew over (a strong sign that you really DO need to provide good 'anchor' soil) was/is a great choice.