starting seeds that need cold

7/28/2019 Starting Seeds That Need Cold

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Starting Seeds

That Need Cold

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STEP-BY-STEPStarting Seeds ThatNeed ColdText by JANET H. SANCHEZIllustrations by ELAYNE SEARS

M A N Y P L A N T S T H A T AREN A T I V E to temperate regions ofthe world have seeds that req uire amoist, cold period beforethey sprout. You can grow these seeds by sowing them inpotsand setting the pots outdoors inlate fall orwinter. Known as"stratification," this treatment replicates the natural condi-tioning the seeds would unde rgo intheir native habitat,breaking down the internal mechanisms that inhibit theirability togerminate. The seeds will germinate when tempera-tures rise inthe spring.

This rather low-tech method, which isalso called moist-chilling, works well for starting seeds ofmany perennials ,including bleeding heart (Dicentra spp.), columbine (Aquilegiaspp.), globeflower (Trollius spp.), masterwort (Astrantia spp.),monkshood (Aconitum spp.), penstemon , garden phlox, andturtlehead (Chelone spp.). It's also very useful forstarting theseeds ofmany fall-ripening trees and shrub s, such asbarber-ries, dogwoods, lilacs, species roses, and viburnums.

I . Sow the SeedsYou can use four-inch plasticpots orflats forthis project. Ifyou have used the containersbefore, clean them first with asolution ofone part house-hold bleach tonine partswater. Prepare apotting mixof equal parts builder's sandand apeat-based potting mix.Th e coarse texture ofthis mixwill allow plenty of air to cir-culate around the seeds andthe growing roots. Moistenthe mix and fill your contain-ers, tamping each down towithin one-half inch ofitsrim. Sow the seeds about a

half-inch apart and coverthem with athin layer ofmix.Topping the pots with a thinlayer ofvery fine gravel orcoarse sand will prevent therain from washing out thepotting mix and the seeds.

Label each container withthe plant 's name and thedate. (Use a permanen tmarker so itwill survive theelements.) Water the potswell toensure that the seedsimbibe moisture, which isanecessary prelud e toth echilling period.

2. Place the Pots in aCold PlaceFor the winter chillingperiod, choose a locationou t ofdirect sun, such as anunheated porch orshed,oran uncovered cold frameon the north side ofth ehouse. Aplace where tem-peratures remain between35 and 45 degrees F ahre n-heit isideal. (Higher a ndlower temperatures wil l

produce changes inth eseeds at aslower rate.) Ifyou opt for acold frame,line itwith a layer ofmoistsand soyou can bury thebase ofthe pots tohelpkeep them up right . Cover-ing the pots with wirescreen will keep outrodents and birds .

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3. W ait for G ermination

4. Thin or TransplantWhen the seedlings havegrow n their second set oftrue leaves, thin or trans-plant them to prevent over-crowding. If you don't needmany plants, thin to oneseedling per pot by cuttingoff the extras with smallscissors. Ifyou want alot ofplants, transplant theseedlings, one per container,into 2 1/4- or 3-inc h-w ideplastic pots filled withmoist, peat-based pottingmix. Use afork to gently lift

the seedlings out of theiroriginal containers andtease them apart. Handlethe seedlings by their leavesto avoid da magin g theirstems.

Water the seedlings andplace them out of direct sunfor afew days to recover.After aweek, put them in aplace where they receivemorning sun. Begin feedingthe seedlings once aweekwith liquid fertilizer dilut-ed to half strength.

Check your pots frequentlyand water if he top of thesoil mix feels dry. As springapproaches, you shouldbegin to see signs of gro wt h.Different species will germi-nate atdifferent rates. Somemay app ear in very earlyspring, others in ate spring,while afew kinds may take

up to ayear or more.As the seedlings sprout,

move the pots to a nurseryarea oran unheated green-house where they receivebright but indirect sunl ight .Kee p an eye out for slugsand snails, which candevour you ng seedl ingsovernight .

5. Plant the Seedlings in the GardenBy late summer orearlyfall, many of your seedlingswill be large eno ugh to setin to the garden. Transplantthem on acool day, andwate r carefully for a fewweeks afterwards until they

are well established. Someslower-grow ing speciesmay not be large enough tomove yet. Keep these in acold frame over winter andset them out the followingspring.

A L T E R N A T I V E C O O L I N G M E T H O D S Ifyou live na warm-winter cl imate, or fyou want toplant in hespring orsummer, you can provide aperiod ofmoist chill-ing by placing already sown pots ofseed in he refrigera-to r fo r abo ut six weeks. Altern atively , stratify the seedsbetween layers ofdamp sand in aplastic bag in he refrig-erator. Sow the seeds as soon as they sprout, orafter sixweeks.J.H.S.

S O U R C E S OFSEEDS Many horticultural societieshold seed exchanges, which are excellent sources ofuncommon varieties. For an extensive list, consult Gar-dening by Mail, byBarbara J. Barto n (M ariner Books,1997). A few societies k now n fo r th eir seed exchangesinclude the N or th Am erican Rock G arden Society (P.O.Box 67, Millwoo d, NY 10546-0067; www.nargs.org), theHardy Plant Society (c/o Pam Adams, Little Orc ha rd,Great Co mb erton , nr. Pershore, Wo rcestersh ire, EnglandWR10 3DP), and the Scottish Rock Garden Club (P.O.Box 14063, Edinburg h, Scotland EH 10 4YE).J.H.S.

NOVEMBER/DECEMBER 1998 31


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