Adrian Higgins on fall gardening

Courtesy Ball Horticultural Co.
Sep 17, 2015

Washington Post gardening columnist Adrian Higgins took questions on gardening.

How are the new tomato varieties for disease resistance, specifically blight? A tomato plant can have the best tasting tomatoes ever, but it has to live long enough to bear those tomatoes. Then you have to keep the critters away, but that is a whole 'nother rant.

Tomato harvest is in full swing. I hope you had a chance to read our Local Living story on how breeders are trying to combine the flavor superiority of heirlooms with the vigor of hybrids. In DC, the tomato season crashed with the June monsoons but for those who stuck with it, the season managed to rebound. I'd love to hear your tomato stories for 2015 and, especially, what growing techniques you employed and which varieties did well for you. There are two highly effective ways to address blight, one is to cover the soil with a thick straw mulch and the other is to remove all the lower leaves early on, so that you might have a plant in late May that is 18 to 24 inches high, but with the stem bare below 12 to 15 inches or so (as the lower branches dictate). It looks odd and disfigured, but the upper growth soon fills out. This is aimed at stopping the upward spread of early blight. 

Hi Adrian. Thanks for doing the chats! We only have one spot in our yard sunny enough for a vegetable garden, and so we can't really rotate crops. As a result, I think diseases (esp fungal) have been accumulating, and the tomatoes were very sad this year. Does solarization work, and if so, how long do the results last? We'd be willing to sacrifice a year of garden if it would be worth it.

Solarization is the process of putting plastic sheeting over beds, so the solar gain cooks the soil below and kills (in theory) pathogens and weed seeds. It does work, and without chemicals, the problem is you need to lay the clear plastic for at least a month in summer, so it removes a bed from use during one growing season, in essence. It's also ugly, let's be honest.

Early blight spores are so endemic that I suspect if you started with a clean bed in May your tomatoes would still get blight from imported spores. 

Which variety reaches that perfect intersection between flavor, and resistance to disease?

Even when you create that perfect balance, variables can alter the results, from heavy rains, to too much overhead irrigation, to soil that is too heavy or poor. The acid test is how does a given variety perform in your garden? I am a big fan of Cherokee Purple and of Brandy Boy, in seeking heirloom qualities with disease resistance and yield.  

I tried solarizing again this summer but the June rains made it useless. Do you know enough about El Ninos to predict what next spring & summer will be like, since they're saying a strong El Nino is working up right now?

And something I forgot to mention about solarization: It brings with it a real risk of trapping water and causing mosquito outbreaks. A strong El Nino would be good in bringing rain to California, I'm not quite sure of its effects here. But we do need rain. In spite of last weekend's downpour, everything is dry and stressed. 

Adrian - I'll need to prune back some lacecap hydrangeas under my kitchen window because of some repair work being done on our house. Is this a good time? (not that I have any choice in the matter - the work needs to be done.)

The buds have already been set for next year, so you will lose flowering wood. Something this is unavoidable. This week, I had to butcher a dwarf nandina in front of the gas meter. But it will grow back, and your hydrangea will rebloom in time. I would make sure that no heavy boots are stomping in the area of the crown of the shrub. 

I planted six Justin Brouwers boxwoods about 2 years ago. They did fine -- until this summer. I picked them because I thought they could take more sun that most boxwoods. But the one that happens to get the most afternoon sun turned a yellow/brown - about 65% of it is dead. I thought it might be the dreaded fungus, but the garden shop thought it was just too hot the last month with not enough water for its shallow roots. Your thoughts? And when I replace it, is there a better choice for that spot? The other 5 are doing relatively well but they get less sun.

Justin Brouwers is a handsome and sturdier substitute for English boxwood, and derived from another species, but it would still benefit from growing in partial shade rather than full sun. The other key to success with boxwood is not to plant them too deeply and not to overwater them. Once they are established, they should be kept on the dry side. I would direct you to the Saunders Bros website and their evaluations of boxwood cultivars. You may find one there that will work better in a full sun situation: Boxwood guide

Although we essentially started a brand new garden last year and rotated the tomatoes to a new spot this year, we had a horrible problem with anthracnose on tomatoes. The small fruited varieties were fine, but the early and canning varieties were hit hard. Now, the deluge of rain in June was likely a big contributor, but we also had trouble last year when rain wasn't as big of a factor. Are there any varieties that are resistant? Besides moving to a new spot in the yard (which didn't seem to make a difference this year) is there anything else we can do?

Anthracnose and blight are similar, although the former is more devastating.I've come to the reluctant conclusion that this isn't the best climate for tomatoes, and to grow them well you either have to find a really open and sunny and breezy site, or spray them before the diseases show up. There are organic sprays available, but this sort of goes against the instincts of gardeners who don't want to use chemicals. 

Lemon Boy is my old reliable. It isn't the best tomato, although it isn't bad for a yellow. But no matter the circumstances, I always get at least a few tomatoes off of it. This year, when the other plants produced only one or two (or none), my Lemon Boy had 6 or 8 tomatoes, not counting the ones that were eaten by birds and animals. I had a bumper crop of paste tomatoes. I can't remember the name, but it was from the Mountain series of disease resistant varieties. This one was advertised as blight resistant, and it really was. Flavor wasn't all that great, even for a paste variety. I plan to check out other Mountain tomatoes.

One bonus of the dry period is that the tomatoes have more flavor and they are not cracking, so we should count our blessings. I've found that varieties can vary quite a bit from one garden to another. When I grew Lemon Boy, I wasn't impressed with the flavor, but it might have been a wet year. 

Pots. I grow them in pots...BIG pots... right amidst the rows of lettuce, beans, whatever, and "mulch" with those hemp planter-liners. But this year the cukes just up and wilted and died on me... is this, too, a "forever" infection? Sigh.

Tomatoes in big pots can work well, especially determinate types. I just wrote about the rooftop container garden at UDC and those Cherokee Purple were productive and flavorful. Some commercial growers actually stress the plants to induce a stronger tomato flavor. 

As for the cukes, this is another unavoidable dimension to cultivating them outdoors -- the beetles arrive and spread the bacterial wilt and suddenly they collapse. One approach is to sow or plant cucumbers successively from early May to late June to assure a long harvest. 

Where locally can one buy established heirloom tomatoes plants outside the usual Brandywine? We prefer to start with extremely established plants because we grow all our tomatoes in half-whiskey barrels for space reasons. Starting from seeds has been frustrating and non-fruitful.

Increasingly, garden centers and local nurseries are offering a broader range of tomato varieties. The pitfall is in buying them in four or six inch pots in early to mid April when it is still too cold. If I buy them, it is in two inch pots in late April for planting in early May. DeBaggios has a good selection at that time, out in Chantilly, Va. . 

Talk about damning with faint praise. My ideal is a fresh-picked Brandywine, which I haven't had for years between bad weather and blight, so would the Cherokee Purple and Brandy Boy be my best bets?

Yes, I think they would stand up to the ills better and be more productive, though you should still give them optimum care. (Sans the spraying?)

We're hoping to grow kale, bok choy, and beets from seed this fall. We only got the beets in last week. Are we too late to get a crop of the others if we plant this weekend or next? I feel panicked by the sudden nighttime drop in temperatures.

Beets may grow a little this fall but then you could harvest them in the spring if the winter isn't as bad as last. I am still sowing hardy greens, kale, mustard greens and spinach. I also plan to re-sow lettuce that didn't germinate (old seed, hot soil). Might still be time for pac choi, especially a dwarf variety.  

Hi Adrian, I have a cluster of the "mini" crape myrtles that were all the rage a few years ago. the pinky-orange ones are blooming like gang-busters (I trim them back each spring)... but the white ones have grey dust on the leaves and NO blooms whatsoever. time to tear out? or time for modern chemistry? thanks,... and I DO so miss your weekly discussions!

The dryness of late has been great for encouraging powdery mildew, which you will now see on lilacs, squash, phlox, all the usual suspects. Modern crape myrtle varieties, including dwarf ones, have been bred for mildew resistance. When I used to spray against mildew I found even that didn't help much in a year like this one. If they're not blooming (too much shade?) and they sickly, I might consider taking them out. 

How much longer do I have to overseed my lawn?

Until mid October. Make sure you have good seed to soil contact by roughing up the lawn with a thatching rake and adding some amendments. Keep it moist and be patient, cool season fescues can take three weeks to germinate. Someone once asked me why his grass seed hadn't sprouted and when I asked him when he'd sown it, he said, "yesterday."


A friend has planted a lot of these and has invited me to help harvest. Do we need to wait for first frost, or can we dig up the tubers now? We're in southern Michigan...

They are usually harvested after the first frost or two has killed the top growth. This will make them sweeter. 

Buy them at a farmers' market---many varieties are sold at Courthouse, and I imagine other markets as well. When trying to start from seed, did you use a grow light? That us usually where seed starters go awry, trying to grow them in a windowsill. Use a good seed starting medium and a light, and you will be surprised how easy it is, and then you the sky is the limit with seed varieties!

I have some homemade light tables with shop lights, and I start the tomatoes in late February, early March. I use heat mats to speed germination. I pot them on after about four weeks.    

I found a great variety of heirloom tomato plants at a vendor at this year's Maryland Sheep & Wool Festival, and I bought an Abe Lincoln. Sadly I had to throw in the towel on tomatoes this year, but would an Abe Lincoln be worth trying again next year?

I haven't grown this variety, but I hear the Sheep and Wool Festival is a great place to find heirloom transplants. I would try it again next year, yes. This is how we grow as gardeners, trial and error. 

Interesting. The garden center told me the browning was most likely from lack of water -- not too much.

Possibly, but the single greatest cause of boxwood death is planting the crown too low in soil that doesn't drain sufficiently. Excessive mulching doesn't help, either. You can test the soil moisture with your fingers. 

Our huge Japanese maple is dying, probably of old age. It's the kind that has thick trunks that spread out from near the ground. We want to put a similar tree a little distance away from where the original is, but I've been looking all over at Japanese maples and they mostly seem to be the slim-trunked kind that's been pruned into a rose-tree kind of shape. What kind do I need to look for? Yes, I realize that we won't live to see the new one as big as the old one.

There are three basic forms of Japanese maples or acers, the weeping, mounded dissectums, the upright ornamental tree (Bloodgood etc.) and a whole host of upright multistemmed shrubs that are the least grown and perhaps the most interesting. Garden centers are increasingly making these available, but you can also find specialty nurseries online. 

I've been reading a lot about pawpaws lately. Do deer eat them? (If so, I'll fence them in.) And do they like sun or shade?

Pawpaws are fruiting now, they take five years after planting to fruit, and will grow in full sun or partial shade. I have a friend  in deer territory and they seem to leave the pawpaws alone, although when it comes to deer and plants, there are no guarantees. 

The blooms get brown and crispy--I obviously can't water it enough to prevent, and it is too big to move. Should I plant something in front of it to offer some shade, or cut to the ground and then move when it is manageable?

It would need rich, moist soil and benefit from partial shade. Now is the time to move all this stuff, but I'd water the beds thoroughly a day or two beforehand. Sorry, we've run out of time. Let's hope for rain. I hope to see you here again before the end of the growing season. Thanks for all your questions. 

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Adrian Higgins
Adrian Higgins is The Washington Post's gardening columnist. Read his latest columns and stories here and follow him on Twitter.
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